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VIROLOGY
1796:Edward Jenner (1749-1823)
 used cowpox to vaccinate against
   smallpox
 was the first person to deliberately
   vaccinate against any infectious disease
 used a preparation to elicit an immune
   response.
 Variolation

  – infecting people with smallpox
  – to protect them from the worst type of
     the disease
1885: Louis Pasteur (1822-1895)
 experimented with rabies
  vaccination
 using the term "virus" to describe
  the agent
 "virus" and "vaccination" (in honor
  of Jenner)
1886: John Buist
 Scottish pathologist
 stained lymph from skin lesions of a
  smallpox
 – "elementary bodies"
 – he thought were the spores of
    micrococci
 – smallpox virus particles
1892: Dmiti Iwanowski (1864-
  1920)
 described the first "filterable"
  infectious agent
 – tobacco mosaic virus (TMV)
     smaller than any known bacteria
     first to discriminate between
      viruses and other infectious
      agents
1898: Martinus Beijerinick (1851-
  1931)
 – extended Iwanowski's work with
   TMV
 – developed the concept of the virus
   as a distinct entity
Freidrich Loeffler (1852-1915)
  and Paul Frosch (1860-1928)
 – demonstrated that foot and
   mouth disease
 – first to prove that viruses could
   infect animals as well as plants
1900: Walter Reed (1851-1902)
 demonstrated that yellow fever is
  spread by mosquitoes
 first to show that viruses could be
  spread by insect vectors such as
  mosquitoes
1908: Karl Landsteiner (1868-
  1943) and Erwin Popper
 proved that poliomyelitis: virus

 proved that viruses could infect
  humans as well as animals
1911: Francis Peyton Rous (1879-
  1970)
 demonstrated that a virus (Rous
  sarcoma virus) can cause cancer in
  chickens
 first person to show that a virus
  could cause cancer
1915: Frederick Twort (1877-1950)
 discovered viruses infecting bacteria
1917: Felix d'Herelle (1873-1949)
  – independently discovered viruses of
    bacteria
  – coins the term bacteriophage
1938: Max Theiler (1899-1972)
 developed a live attenuated vaccine
  against yellow fever
 safe and effective that it is still in
  use today!




1940: Helmuth Ruska (1908-1973)
 used an electron microscope: virus
  particles
 direct visualization of virions
1941: George Hirst
 demonstrated that influenza virus
  agglutinates red blood cells
 viruses could be counted


1945: Salvador Luria (1912-1991)
  and Alfred Hershey (1908-1997)
 demonstrated that
  bacteriophages mutate
 antigenic variation in viruses.
1957: Alick Isaacs and Jean
  Lindemann
 discovered interferon

 – first cytokines to be studied in
    detail
Carleton Gajdusek
 – proposed: a "slow virus" is
    responsible for the prion disease
    kuru
 – kuru is similar to that of scrapie
 – kuru can be transmitted to
1961: Sydney Brenner, Francois
  Jacob, and Matthew Meselson
 demonstrated that bacteriophage
  T4 uses host cell ribosomes
 – to direct virus protein synthesis
 – fundamental molecular
   mechanism of protein translation.
1963: Baruch Blumberg
 discovered hepatitis B virus (HBV)
 developed the first vaccine against
  the HBV
 – first vaccine against cancer

1989: Hepatitis C virus (HCV)
 nonA, nonB hepatitis
 first infectious agent to be identified
  by molecular cloning of the genome
    Sending Specimens to the
    Laboratory
    –Right specimen
    –Taken at the right time
    –Stored and transported
      immediately
Specimens for viral isolation or Ag
              detection
Respiratory Infection Nasal or throat
  
                       swabs, postnasal
                       washings
Gastrointestinal infxn Feces
Vesicular rash        Vesicular fluid, throat
                      swab, feces
Hepatitis             Serum, feces
CNS                   CSF, throat swab,
                      feces
AIDS                  Unclotted blood
SPECIMENS:
 Blood serum
  – syringe
  – vacutainer
 Swabs
  – skin lesions
  – throat
  – transport medium
     antibacterial
     antifungal
   Vesicle fluid
    – tip of a scalpel blade
    – large needle
    – spread on a slide
   CSF
    – dry sterile container
   Feces
    – dry sterile container
    – rectal swab
   Storage:
    – secure plastic bags
    – labeled
    – transported ASAP
    – 4oC: overnight
   Request forms:
    – date on onset of disease
    – clinical signs
    – suspected diagnosis
Laboratory Diagnosis
         for
        viral
     Infections
3 Basic categories of methods
used in the Diagnosis of virus
          infections
     Direct   Examination

     Indirect   examination

     Serology
Direct Examination
Clinicalspecimen
 examined directly for
 presence of virus
 particles, virus
 antigens, viral nucleic
 acids and virus-induced
 histological changes
Direct Examination
Clinical   specimen
 –virus particles
 –virus antigens
 –viral nucleic acids
 –virus-induced histological
  changes
Direct Examination
Main advantage: short
 length of time required for
 result
Results available the same
 day
specific antiviral
 chemotherapy
Direct Examination
Automated  molecular
biology techniques
available:
 1. PCR-based amplicor
     system
 2. Abbott LCR system
 3. Chiron branched DNA
     system
Direct Examination
 Wave of the future:
DNA chip technology
 detect viruses from
     clinical specimens
 tell viral load
 determine antiviral agent
     the virus is sensitive to
Indirect Examination
Virus amplification:
  growing in tissue culture, eggs or
 animals
Growing virus: changes
 cytopathic effect (CPE)
 ability to hemadsorb
Identity of virus confirmed by:
 virus neutralization
 Immunofluorescence
 complement fixation
 electron microscopy
Indirect Examination
Disadvantage of virus culture:
 long time required for CPE
 ability to hemadsorb to become
 apparent
May take a few days to a few
weeks
Virus culture sensitivity: low and
depends on quality of clinical
specimen received
Not applicable to viruses that are
difficult or can not be cultivated
SEROLOGY
Remains the bulk of work carried
out by a routine diagnostic
laboratory
 Complement fixation test
 hemagglutination-inhibition
 enzyme linked immunoassay
 Radioimmunoassay
 particle agglutination
 Immunofluorescence
 single radial hemolysis
 western blot
SEROLOGY
Sensitivity and specificity rates vary
Most techniques will detect all
classes of antibody
Some assays like RIA, EIA and IF
can be made to detect one specific
class
 IgM, IgG, IgA
Virus infections usually diagnosed
by serology:
  * hepatitis A, B and C
DIFFICULT VIRUSES
Viral infections of the Central
nervous system
 infection in immunocompetent
            hosts
 infection caused by HIV and
 opportunistic infections
Viral pneumonias
Viral skin infections
Emerging viral infections
Viral infections of the CNS
 Most  cases of acute encephalitis in
  immunocompetent hosts due to:
   * HSV-1 and HSV-2
   * EBV
   * HHV-6 and HHV-7
 Among immunocompromised
  individuals:
   * CMV
   * VZV
Viral infections of the CNS
Diagnosis revolutionized
 by availability of
 cerebrospinal fluid (CSF)
 polymerase chain reaction
 analysis
PCR allows rapid, specific
 and sensitive diagnosis
Viral infections of the CNS
 CSF-PCR   instead of brain biopsy
 – Dx standard for HSV encephalitis
 – mild or atypical cases
   16-25%     of cases
 HSV
    PCR analysis of CSF
 –monitoring adequacy of therapy
 –14day treatment with acyclovir
      negative PCR
 Prognosis:
 – Determination of number of viral
  DNA copies
Viral infections of the CNS
 EBV  semi-quantitative PCR
  –significantly higher: active EBV
   infection
  – latently infected patients
   seropositive: LOWER
 positive EBV PCR in CSF

  –sensitive and specific
    primary CNS lymphoma in
     patients with AIDS
    CNS mass lesions
Viral infections of the CNS
 HHV  6 and HHV 7
   –Almost all children
   –PCR
 review of CSF specimens from
  patients initially suspected to have
  HSV encephalitis found HHV 6 DNA
  in ~ 7% of specimens
   – suggests HHV 6 may be an
    important cause of sporadic focal
    encephalitis
Viral infections of the CNS
 Using  CSF RT-PCR analysis
   –most cases (85-95%) of acute
    viral meningitis
      enteroviruses
 Signs and symptoms indicative of
  encephalitis rather than
  meningitis develop in ~ 3% of
  patients
 Patients with
  agammaglobulinemia are at risk
  for chronic enteroviral
  meningoencephalitis
Viral Pneumonias
   Causes in adults:
    * Adenovirus         * Influenza A & B
    * CMV                * Measles
    * HSV                * Parainfluenza
                            virus
    * RSV                 * VZV
   Causes in children
    * Influenza A & B       * Measles
    * Parainfluenza         * RSV
Diagnostic techniques for
         herpesvirus infections
Virus     Cytologic Viral      Antigen   Gene
          evaluation culture   detection ampli-
                                         fication
HSV       Cowdry       CPE     IFA       PCR
          Type A       SVA     ELISA
          bodies
VZV       Cowdry       CPE     IFA       MRT-PCR
          Type A
          bodies
CMV       “owl’s       CPE     IFA       MRT-PCR
          eye” cells   SVA     ELISA
Diagnostic techniques for
         herpesvirus infections
Virus       Cytologic Viral       Antigen   Gene
            evaluation culture    detection ampli-
                                            fication
            Highly          CPE   IFA       MRT-PCR
RSV         eosinophilic
            intracytoplas   SVA   ELISA
            mic
            inclusions
Para        Large cells     HA    IFA      MRT-PCR
            with single
influenza   nucleus &       SVA   ELISA
            multiple
            small
            eosinophilic
            inclusions
Measles                     HA    IFA
                                  ELISA
Diagnostic techniques for
           viral infections
Influenz       HA      IFA
a virus        SVA     ELISA



Adeno Intra-     CPE   IFA     MRT-
virus nuclear SVA      ELISA   PCR
      inclusions
Herpes virus skin infection
            Diagnosis
 Tzanck  preparation :
  –used to rapidly determine presence
    of HSV or VZV
  –does not distinguish between these
    2 viruses
 Stains : Giemsa,Wright’s, methylene
             blue
 Characteristic multinucleated giant
  cells
  – inexpensive, efficient provisional
     diagnosis
Herpes virus skin infection
          Diagnosis
 HSV  tissue culture: using
  monoclonal antibodies, requires
  only 24 hours
  –sensitive test but expensive
 Polymerase chain reaction

  –expensive
 Serology not very useful
  – general population has antibodies to
    herpes simplex
Emerging Viral Infections
 Acute   Hemorrhagic fever syndromes:
  – Ebola and Marburg v
  – Hantavirus
  – Arena virus
 Other   viral encephalitis agents:
  – Nipah virus (previously unknown
    paramyxovirus)
 Labtesting currently available
 only at CDC:
 –antigen detection
 – IgM antibody detection
 –isolation in cell culture
 –visualization by electron
  microscopy
 – immunohistochemical
  techniques
 –RT-PCR
Emerging Viral Infections
 Many  of these “emerging” viral
  infections are thought to pose a
  serious risk as biologic weapons
 Rapid diagnostics should be
  made available worldwide in
  order to detect as rapidly as
  possible both justified and
  unjustified suspects of HF and
  attacks by other “biological
  weapons”
Emerging Viral Infections
 SARS

  –Severe acute respiratory syndrome
  –Killer pneumonia
 Cause has yet to be identified

 Laboratory tests found two types of
  virus:
  –paramyxovirus
  –corona virus
 A rapid diagnostic test should come
  soon
SUMMARY
Despite enhanced
laboratory techniques such
as viral culture, rapid
antigen detection and gene
amplification, a confident
diagnosis of viral
pneumonia continues to be
a CHALLENGE
SUMMARY
The non-specific nature of
 clinical characteristics &
 the extreme sensitivity of
 lab techniques make the
 diagnosis difficult, even
 when a viral agent is
 detected
SUMMARY
Understanding the
 limitations of these
 technological advances
 and the use of
 histopathological
 techniques can greatly
 enhance a skilled
 clinician’s ability to make
 an accurate diagnosis
ADENOVIRUS
ADENOVIRUS
DNA viruses first isolated
from adenoidal tissue in
1953
ADENOVIRUS
Family   Adenoviridae
Genus    Mastadenovirus
Transmission electron micrograph
         of adenovirus
           Source- PHIL, CDC
ADENOVIRUS - Classification
•   Subdivided into 6 subgroups based on
•   hemagglutination (A-F)

•   Human pathogens belong to 49 serotypes

•   Common serotypes:- 1-8, 11, 21, 35, 37, 40

•   Enteric Adenoviruses belong to subgroup F
ADENOVIRUS - Structure

   Non-enveloped DNA virus

   70-90 nm in size

   Linear ds DNA genome with core proteins
ADENOVIRUS
 EM APPEARANCE
ADENOVIRUS - Ultrastructure
   Icosahedral capsid with 252 capsomeres

    (12 pentons at vertices and 240 hexons)

   Each penton has a fibers with terminal
    knob projecting from it
Adenovirus- 3 D structure
Adenovirus - EM
       appearance
Note- projecting fibers and terminal knob
ADENOVIRUS-Ultrastructure
ADENOVIRUS STRUCTURE
Structure
Pathogenesis and Replication
• Infects   mucoepithelial cells of
 respiratory, GI and GU tracts
• Enter   via epithelium, replicate
 and spread to lymphoid tissue
• Viremia   occurs
• Secondary    involvement of
Pathogenesis and Replication
                   (contd.)

 Fiber   protein determines target cell
 specificity and attachment

 Viral   DNA enters host cell nucleus

 Virus   replicates in cytoplasm
Adenovirus- replication
Replication (contd.)

•   Early and late phases of

replication

•   Errror-prone process

•   Inclusion bodies in nucleus
ADENOVIRAL INCLUSION
      BODIES
Types of infection
   Lytic
   Latent/occult
   Oncogenic Transformation
Types of infection
 Lytic

 Results in cell death; seen in mucoepithelical
 cells
 Latent/occult

 Virus remains in host cell; seen in lymphoid
 tissue, Groups B and C
 Oncogenic    Transformation
 Uncontrolled cell growth and replication
 occur; seen with Group A viruses in
 hamsters
Adenovirus
 Used as VECTORS to transfer desired
  genetic material into cells e
 Viral genome is relatively easily
  manipulated in vitro
 Efficient expression of inserted DNA in
  recipient cell
Adenovirus- Properties

 Stable   in the environment

 Relatively   resistant to disinfection

 (Alcohol, chlorhexidine, detergents)

 Stable   in GI tract- can withstand low
 pH, bile acids and proteolytic enzymes
Time-course of infection
 Incubation    period- 2-14 days
   Infective period continues for weeks
   Intermittent and prolonged rectal
    shedding
   Secondary attack rate within families up
    to 50%
Timecourse - Respiratory infection
  Source- Medical Microbiology- Murray, Rosenthal, Kobayshi and Pfaller
EPIDEMIOLOGY

Endemic,   epidemic and sporadic infections

Many   infections are subclinical
EPIDEMIOLOGY-contd.
 ”Tip of the iceberg phenomenon”


                 Classical disease presentation
                            Mild clinical disease




                       Asymptomatic infection
                           but infectivity (+)
Epidemiology of Adenoviral
        Infections
 (source-centers for disease control and prevention)
EPIDEMIOLOGY

Outbreaks noted in military recruits,

swimming pool users, hospitals,

residential institutions, day care settings
EPIDEMIOLOGY-transmission


 Prolonged   infective period (weeks)
 Intermittent   and prolonged rectal
 shedding
 Stable   in the environment
TRANSMISSION

•   Droplets
•   Fecal-oral route
•   Direct and through poorly chlorinated water
•   Fomites
CLINICAL
    SYNDROMES
•   Respiratory
•   Eye
•   Genitourinary
•   Gastrointestinal
•   Others
Acute Respiratory Disease
              (LRI)

 Fever

 Tracheobronchitis
 Pneumonia
 Childrenand adults
 Epidemics in military recruits
 Types 4 and 7 most frequently
Acute Respiratory Disease
Pharyngoconjunctival fever
   Headache, fever, malaise
   Conjunctivitis and Pharyngitis

   Cervical adenopathy, rash and diarrhea
    also

   Main adenovirus types: 3, 4, 7, 14

   Epidemics in summer months
   Contaminated water in swimming pools,
    fomites
Adenoviral Infections of the eye

   Epidemic Keratoconjunctivitis (EKC)

   Acute follicular conjunctivitis

   Pharyngoconjunctival fever
Adenoviral Infections of the
            eye
Epidemic Keratoconjunctivitis

   Incidence in summer
 Conjunctivitis usually followed by
  keratitis
 Headache

   Pre-auricular lymphadenopathy
   Types 8, 19, 37
   Nosocomial spread by fomites, hands,
    ophthalmologic equipment, medications
Gastrointestinal Infections
 Types   40, 41
 Age    <4 years
 Spread   via fecal-oral route
 Year   round
Gastrointestinal Infections-
                 (contd.)


 Incubation   period 3-10 days
 Diarrhea   lasts for 10-14 days
 Fever

 Also,
      intussusception, mesenteric
 adenitis, appendicitis
INTUSSUSCEPTION
ADENOVIRAL INFECTIONS-
      Genitourinary system
Acute hemorrhagic cystitis
 fever, dysuria, hematuria
 Types 11, 7, 4, 21, 1
 More common in boys



Others
 Orchitis, nephritis, cervicitis with
  ulcerated vesicular lesions
 Types 2, 19, 37
Other Infections due to
       Adenovirus

•Myocarditis

•Pericarditis

•Meningitis

•Rash

•Arthritis
Adenovirus infections in
      Immunocompromised hosts

   Disseminated, severe and often fatal
    infections
   Due to new infection or reactivation of
    latent virus
   Prolonged infections with prolonged
    viremia and viral shedding
   Necrotizing pneumonia, hepatitis, rash,
    DIC, CNS involvement
Adenovirus infection in the
  immunocompromised
DIAGNOSIS
   Variety of clinical specimens depending on
    clinical syndrome-NP, conjunctival, stool,
    urine,
    tissue, etc.
   Transport in viral transport media
   Isolation from pharyngeal site correlates
    better with current clinical infection
Methods for diagnosis

   Culture in HeLa, HEK cell lines
   Shell vial cell culture
   DFA
   PCR, nucleic acid probes
   EM and Immune EM
Diagnosis-
      Enteric adenoviruses


 Isolation
         requires special media-
 Graham 293

 ELISA for rapid detection is
 available
Prevention
   Good handwashing
   Contact precautions
   Chlorination of water
   Disinfection or
    sterilization of
    ophthalmologic
    equipment
   Use of single dose vials
   Oral vaccine- restricted
HIV and AIDS
The cellular and immunological picture - The course of
the disease
HIV and AIDS
The cellular and immunological picture - The course
of the disease
HIV and AIDS
The cellular and immunological picture
The course of the disease

1. Acute Infection
 • High virus titer
 • Mild symptoms
 • Fall in CD4+ cells but recovers
 • Rise in CD8+ cells but recovers
 • A high virus titer (up to 10 million
    Macrophages bring HIV into the body if se
 viruses per ml blood)
HIV and AIDS
      2. A strong immune response



Virus almost disappears from circulation
• Good cytoxic T cell response
• Soluble antibodies appear later against both
surface and internal proteins
• Most virus at this stage comes from recently
activated (dividing) and infected CD4+ cells
HIV and AIDS
                       3. A latent state


Latency of virus and of symptoms
• Virus persists in extra-vascular
tissues
• Lymph node dendritic cells
• Resting CD4+ memory cells (last a
very
long time - a very stable population of
cells) carry provirus
HIV and AIDS

• 10 billion HIV particles per day
• Virus half life 5.7 hours
• 100-10 million virions per ml blood (set point)
• Small minority of T4 cells are infected
• Virus found in lymph nodes
HIV and AIDS
              4. The beginning of disease
Massive loss of CD4+ cells
• CD4+ cells are the targets of the virus
• Cells that proliferate to respond to the
 virus are killed by it
• Dendritic cells present antigen and virus
 to CD4 cells
• Epitope variation allows more and more
HIV to
escape from immune response just as
HIV and AIDS
 5. Advanced disease - AIDS
CD8+ cells destroy more
CD4+ cells
• CD4 cell loss means virus and
infected
 cells no longer controlled
• As CD4+ cells fall below 200
per cu mm
virus titer rises rapidly and
remaining immune response
HIV and AIDS




           Good correlation betw
           number of HIV particle
           measured by PCR an
           progression to disease
HIV and AIDS



               Viral load predicts
               survival time
HIV and AIDS




           CD4 cell count is not
           good predictor of
           progression to diseas
HIV and AIDS
                   Cofactors
Not all cases of Kaposi’s are associated with HIV
Not all HIV infected persons suffer from Kaposi’s
20% of homosexual HIV+ males get Kaposi’s
Few IV drug users or hemophiliacs get Kaposi’s
        Kaposi’s sarcoma associated herpes virus
        Human herpes virus-8
HIV and AIDS
                     Three Views of AIDS

      Gallo: Infection by HIV is sufficient to cause AIDS

Montagnier: HIV may be harmless in the absence of other co-
factors
Duesberg / Mullis: HIV is too silent to be the etiologic agent of
AIDS. It is a much maligned by-stander

So far it seems that >50% of HIV-infected persons have
progressed to AIDS
There is NO strong evidence there is any other infectious
agent involved than HIV
HIV - The Virus
                   Retrovirus




Membrane: host derived
                   Three genes
                   GAG – POL – ENV
HIV - The Virus
                    Retrovirus




Two glycoproteins: gp160      gp120 and gp41
gp41 is fusogen that spans the membrane
sugars                                    vaccine problem
                       ENV gene
HIV - The Virus
                  Retrovirus

  Group-Specific Antigens

p17: inner surface - myristoylated
p24: nucleocapsid
p9: nucleocapsid associated with RNA
GAG gene
           Polyprotein
HIV - The Virus
  Enzymes         Retrovirus

• Polymerase (reverse
transcriptase – RNA
dependent DNA
polymerase)
• Integrase
          • POL gene
• Protease (cuts
           Polyprotein
polyproteins)
The Genome of HIV




Three structural genes
LTRs
Extra open reading frames are clue to latency
HIV - The Virus
HIV - The Virus

            Life History
      A retrovirus

      • Latency
      • Specific destruction of
      CD4+ cells
HIV - Life History

           • Fusion at ambient pH
           • No need for entry
           into lysosomes
           •Profound significance
             Syncytia
            for AIDS progression:
            Spread from cell to
            cell
           Profound significance
HIV - Life History
       Entry into the cell
       T4 (CD4+) cells are major
       target
                     Human HeLa
 Human
                     Cell transfected
 HeLa Cell
                     with CD4 antigen

NOT INFECTED                 INFECTED
 But NOT the whole answer since this
  does not happen if CD4 is transfected in
HIV - Life History
    Why do CD4-transfected human cell
    but CD4-transfected mouse cells do
  Human cells must possess a co-factor for infection that mou

Co-Receptors
CD8+ Cells


MIP-1 alpha MIP-1 beta RANTES
Chemokines
HIV - Life History


                  HIV


                               chemoki
                                               Mutant
                        CD4    ne
                              CCR5             CCR5
        CCR5                             CD4
  CD4


             macrophage
Chemokine receptors are necessary co-recep
HIV and AIDS
Some people do not get AIDS



Long term survivors
Exposed uninfected persons

  The chemokine receptor story
HIV and AIDS
Co-receptors and HIV infection
• CCR5 is a chemokine receptor
• Cells with homozygous mutant CCR5 molecules are not
infected by HIV
1 in 100 Caucasians
No Africans
• Persons with heterozygous mutant CCR5 molecules
progress to AIDS more slowly
HIV and AIDS

Co-receptors
• 25% of long term survivors are CCR5 or CCR2
mutants (deletions)

• The same CCR5 mutation (called “delta 32”) is
thought to be the mutation that rendered some
people immune to the plague in the middle
ages
         • Many other chemokine receptors
HIV and AIDS
    Long term non-progressers
   People who have been infected with
    HIV for more than seven years that
    have stable CD4+ cell counts above
    600 per cu mm with no symptoms and
    no chemotherapy

    Many have produced a very good
    immune response to the virus
HIV and AIDS


• Nairobi prostitutes
Client infection rate more than 25%
• Rare HLA antigens
• Associations between resistance to infection and their
class I and class II MHC (HLA) haplotypes
HIV - Life History
HIV is a retrovirus
It carries with it:
 • Reverse transcriptase     HIV genes
 • Integrase               GAG POL
 • Protease                ENV

 • tRNA primer
      HIV has no oncogene but could still be oncogenic
                vaccine problem
HIV - Life History
        Latency – Cellular – The problem of memory T4 cells

   Only activated T4 cells can replicate virus
   Most infected T4 cells are rapidly lyzed but are replaced
   Some T4 cells revert to resting state as memory cells wh
   Memory T4 cells cannot replicate the virus unless they b
                     Clinical Latency

HIV infection is not manifested as disease for years
Dynamics of CD4 T cells in an
            HIV infection
         Cell death                                             Chronically-
         apoptosis etc                                          infected
                                                                memory T
                                                 Return to      cells with
                      Infection                  resting
Uninfected                                       state          provirus
activat
ed                 Long
T cell                                          Reactivation
                   lived!
              Uninfected          Cell death                                  Long
              unactivated
              memory
                                  immune                                      lived!
                                                         Adapted from Saag and Kilby
              T cell pool         destruction            Nat Med 5: 609, 1999
Long tern latent HIV


               Immune response


T4 resting                       T4 activated

  It may be impossible to cure the patient o
  Even if combination therapy stops HIV re
                     HIV
Inexorable decline of CD4+
              T4 cells

Why do all
of the T4
cells
At early
disappear?
stages of
infection
only 1 in
10,000 cells
is infected
       Of great importance to therapeutic strategy
Virus destroys the cell as a result of
          budding



         But few cells are infected:
         Early stage of infection 1:10,000
         Late 1:40




                                                   Why do all T4
                                                   cells
1. PUNCTURED                                       disappear?
MEMBRANE
Why do all T4 cells
            disappear? - 2
                                      But syncytia
                                      not common
Infected CD4
                 Cells
cell                                  Most T4 cells
                 Fuse
Gp120                                 are not HIV+
positive

                                      Could
                                      “sweep up”
                         Uninfected
Killing of CD4 cells     CD4 cell     uninfected
2. Syncytium             Gp120        cells
Formation                negative
Why do all T4
                   cells
                   disappear?


                   Cytotox
                   ic T cell



            Killing of CD4 cells
            3. Cytotoxic T cell-
BUT: Most   mediated lysis
cells are
Killing of
CD4+ cells
4. Binding of free
Gp120 to CD4
antigen makes
uninfected T4 cell
look like an
infected cell
Complement-
mediated lysis
Why do all T4 cells
  disappear?
                       Induction of apoptosis
   CD8               gp120
                                    Macrophag
HIVcell                             e
  (no CD4 antigen)
                        chemokin
                        e
                             CXCR
                             4        G protein
                                      signal
                 ?
                                         ?




                                    Binding to
      Binding to
                                    CXCR4
      CXCR4 results                 results in
      in expression                 expression of
      of TNF-alpha                  TNF-alpha on
Why do all T4 cells
disappear?
           Induction of apoptosis
 CD8 cell
    CXCR
    4                   Macrophag
   Deat                 e
   h




               CD8 T
               cell
Macrophages may be infected
       by two routes
HIV   gp120
              CD4
                                 HIV gp120 binds to
                                 macrophage CD4
                                 antigen
                                 Virus is opsonized
                                 by anti gp120
                                 antibodies which
                Fc receptor      bind to macrophage
                                 Fc receptors - an
                    Anti-gp120      vaccine problem
                                 enhancing antibody
          HIV
Overview: Hepatitis
 Virology
 Transmission

 Epidemiology

 Pathogenesis

 Symptoms

 Diagnosis

 Management

 Prevention
Viral Hepatitis - Overview
                             Types of Hepatitis
                 A              B               C               D              E
Source of Feces               Blood           Blood           Blood         Feces
                           Blood-derived   Blood-derived   Blood-derived
Virus                       body fluids     body fluids     body fluids
Route of    Fecal-Oral     Percutaneous    Percutaneous    Percutaneous     Fecal-
Trans-                      Permucosal      Permucosal      Permucosal       Oral
mission
Chronic     No                 Yes             Yes             Yes            No
Infection
Primary     Pre/Post-        Pre/Post-      Blood Donor      Pre/Post-     Ensure safe
            Exposure         Exposure        Screening       Exposure       drinking
Prevent-                                                   Immunization      water
            Immunization   Immunization
ion                                        Risk Behavior
            Handwashing    Risk Behavior   Modification    Risk Behavior
                           Modification                    Modification
Hepatitis A, B, and C at a Glance
Virus   Sex    IDU    Trans-   Fecal-   Occu-      Course of Infection         Does         Vaccine
                      fusion   Oral     pational                               Protective   Available
                                                                               Immunity
                                                                               Develop?

A       High   Low*   Low      High     None       Acute -> Resolved           Yes          Yes




B       High   High   Low      None     High       Acute -> Chronic            Yes          Yes
                                                   90% of infants
                                                   30% in children aged 1-5
                                                   10% of older children and
                                                   adults.

C       Low    High   Low      None     Low        Acute -> Chronic            No           No
                                                   in 75%-85% of adults.
Age at Infection –
           Viral Hepatitis
         Perinatal   Childhood    Adolescent   Adult
HAV           -         ++++          ++
 +++

HBV        ++                    ++
 +++     +++++

HCV           +           -            +
      +++++
REPORTED CASES OF SELECTED NOTIFIABLE
 DISEASES PREVENTABLE BY VACCINATION,
          UNITED STATES, 2001

   Hepatitis A               10,609
   Hepatitis B                7,843
   Pertussis                  7,580
   Meningococcal disease      2,333
   H. influenzae, invasive    1,597
   Mumps                        266
   Measles                      116

   Source: NNDSS, CDC
HEPATITIS A VIRUS
Hepatitis A Structure
Hepatitis A Virus: Structure and
         Classification

   RNA Picornavirus
    • Separate genus because of differences
      with other enteroviruses
    • Naked icosahedral capsid
    • SS RNA (740 nucleotides)
    • Single serotype worldwide
    • Humans only reservoir
HEPATITIS A VIRUS TRANSMISSION

     •   Fecal-oral transmission

     •   Close personal contact
         (e.g., household contact, sex
         contact, child day-care centers)

     •   Contaminated food, water
         (e.g., infected food handlers,
         contaminated raw oysters)

     •   Blood exposure (rare <<<1%)
         (e.g., injection drug use, rarely
         by transfusion)
HEPATITIS A, UNITED STATES
   Most disease occurs in the context of community-
    wide outbreaks
   Infection transmitted from person to person in
    households and extended family settings
    - facilitated by asymptomatic infection among
    children
   Some groups at increased risk
     – specific factor varies

     – do not account for majority of cases

    –   Children are the most frequently infected group
   No risk factor identified for 40%-50% of cases
DISEASE BURDEN FROM
              HEPATITIS A
          UNITED STATES, 2001


Number of acute clinical    10,609
cases reported

Estimated number of acute   45,000
clinical cases

Estimated number of         93,000
new infections

Percent ever infected       31.3%
GEOGRAPHIC DISTRIBUTION OF
HEPATITIS A VIRUS INFECTION
NUMBER OF YEARS REPORTED INCIDENCE OF
HEPATITIS A EXCEEDED 10 CASES PER 100,000,
            BY COUNTY, 1987-1997




       0-1    2-3   4-5    6-7    8-11
Hepatitis A: Pathogenesis

   Incubation 4 weeks (range 2-6 weeks)

   Oral cavityGI tractliver via blood

   Replicates in hepatocytes (little damage
    to cells) released via bile to intestines
    7-10 days prior to clinical symptoms

   Liver damage and clinical syndrome
    result of immune response and not
    direct effect of virus
Hepatitis A: Clinical Features
– An acute illness with:
    discrete onset of symptoms (e.g.
     fatigue, abdominal pain, loss of
     appetite, intermittent nausea, vomiting)
   jaundiceor elevated serum
    aminotransferase levels, dark urine, light
    stool
   Adults   usually more symptomatic
   Patients are infective while they are
    shedding the virus in the stool- usually
    before the onset of symptoms
   Mostcases resolve spontaneously in 2-4
    weeks
   Complete   recovery 99%
HEPATITIS A - CLINICAL FEATURES

•Jaundice by           <6 yrs     <10%
  age group:             6-14 yrs
40%-50%
                              >14 yrs
70%-80%
•Rare complications:   Fulminant hepatitis
                         Cholestatic
hepatitis
                         Relapsing
hepatitis
•Incubation period:    Average 30 days
                         Range 15-50 days
EVENTS IN HEPATITIS A VIRUS INFECTION
                                Clinical illness


           Infection                  ALT

                                               IgM                 IgG
Response




                  Viremia


                           HAV in stool


              0   1    2    3     4   5    6       7   8   9   10 11 12 13
                                       Week
Hepatitis A Diagnosis
 Detection of IgM antibody
 IgG positive 1-3 weeks later;
  suggests prior infection or
  vaccination.
Hepatitis A Treatment
 Supportive-   no specific role of
  antiviral therapy
 Lifelong immunity likely after
  infection or vaccination
PREVENTING HEPATITIS A

• Hygiene (e.g., hand washing)
• Sanitation (e.g., clean water
  sources)
• Hepatitis A vaccine (pre-exposure)
• Immune globulin (pre- and post-
  exposure)
HEPATITIS A VACCINES

• Inactivated vaccine
• Highly immunogenic
    •97%-100% of children, adolescents, and
   adults have protective levels of antibody
   within 1 month of receiving first dose;
   essentially 100% have protective levels
   after second dose

• Highly efficacious
    •In published studies, 94%-100% of
   children protected against clinical hepatitis
   A after equivalent of one dose
HEPATITIS A VACCINES

1st dose at time 0

2nd dose 6-12 months afterwards
POST-VACCINATION TESTING

Not recommended:
  High   response rate among vaccinees

  Commercially  available assay not
  sensitive enough to detect lower
  (protective) levels of vaccine-induced
  antibody
DURATION OF PROTECTION AFTER
           HEPATITIS A VACCINATION

 Protection begins 4 weeks after vaccine
 Persistence of antibody
    •   At least 5-8 years among adults and
        children
   Efficacy
    –   No cases in vaccinated children at 5-6 years
        of follow-up
 Mathematical models of antibody
  decline suggest protective antibody
  levels persist for at least 20 years
 Other mechanisms, such as cellular
  memory, may contribute
Hepatitis A Vaccine
                Recommendations
   Vaccine is recommended for the following
    persons 2 years of age and older:
    – Travelers to areas with increased rates of hepatitis A
    – Men who have sex with men
    – Injecting and non-injecting drug users
    – Persons with clotting-factor disorders (e.g.
      hemophilia)
    – Persons with chronic liver disease
    – Children living in areas with increased rates of
      hepatitis A during the baseline period from 1987-
      1997- mainly West Coast.
Hep A : Passive Immunization
 Hepatitis  A immune globulin can be
  given up to 2 weeks after an
  exposure
 Immunity temporary (4-5 months)

 Also given in travelers leaving for
  endemic area on short notice (ie not
  enough time for the vaccine to be
  effective)
Hepatitis A Surveillance & Response

   Urgently reportable condition in S.C. –
    Acute HAV infection must be reported
    by phone to DHEC within 24 hours.


   Investigation of a case of hepatitis A
    must be initiated by CO DADE and
    district epi staff within 24 hours of
    notification.

   All cases must be reported to CDC.
Hepatitis B Virus
Hepatitis B: Structure
 Member of the hepadnavirus group
 Virion also referred to as Dane particle
 42nm enveloped virus
 Core antigens located in the center
  (nucleocapsid)
    – Core antigen (HbcAg)
    – e antigen (HBeAg)- an indicator of
      transmissibility (minor component of the
      core- antigenically distinct from HBcAg)
   22nm spheres and filaments other
    forms- no DNA in these forms so they
    are not infectious (composed of surface
    antigen)- these forms outnumber the
    actual virions
Structure and Replication
   Circular partially double stranded DNA of virus
   Initial replication to complete circular DNA
    with subsequent transcription to make several
    mRNAs some of which are translated into viral
    proteins

   One of the mRNAs is replicated with a reverse
    transcriptase making the DNA that will
    eventually be the core of the progeny virion
   Some DNA integrates into host genome
    causing carrier state
   Virus stable and resist many stresses making
    them more infectious
Hepatitis B virus particles
Epidemiology - United States1

           100,000 new infections per year
           8,000 - 32,000 chronic
            infections/year
           5,000 - 6,000 deaths/year
           1.25 million Americans with chronic
            HBV infection
              – 15 to 25% of chronically infected
                patients will die from chronic liver
                disease
1.   Center for Disease Control
Geographic Distribution of Chronic HBV Infection




                    HBsAg Prevalence
                        8% - High
                        2-7% - Intermediate
                        <2% - Low
High Prevalence of CHBV in Asian
American Communities is Often Overlooked1
 US prevalence for chronic HBV is < 2%
 However, chronic HBV prevalence of 10-
  15% in Asian American communities has
  been reported
 In Asian American men living in
  California, HCC ranks as a leading cause
  death
     – #2 in Vietnamese and Cambodian Americans
     – #4 in Chinese and Korean Americans
    50% of children born to mothers with
     chronic HBV in the US are Asian American
1.   www.liver.stanford.edu
Hepatitis B Virus
Modes of Transmission


     • Sexual
     • Parenteral
     • Perinatal
Concentration of Hepatitis B Virus
      in Various Body Fluids

                               Low/Not
    High        Moderate      Detectable

   blood        semen           urine
   serum      vaginal fluid     feces
wound exudates saliva           sweat
                                tears
                              breastmilk
Risk Factors for Acute Hepatitis B
              United States, 1992-1993
                                              Heterosexual*
                                                     (41%)



   Injecting
     Drug
      Use                                                 Homosexual Activity
    (15%)                                                 (9%)


                                                        Household Contact
                                                        (2%)
                                                     Health Care Employment
                                                     (1%)
                            Unknown (31%)
                                                   Other (1%)

* Includes sexual contact with acute cases, carriers, and multiple partners.
 Source: CDC Sentinel Counties Study of Viral Hepatitis
HBV Pathogenesis
 Virus enters hepatocytes via blood
 Immune response (cytotoxic T cell) to
  viral antigens expressed on hepatocyte
  cell surface responsible for clinical
  syndrome
 5 % become chronic carriers (HBsAg> 6
  months)
 Higher rate of hepatocellular ca in
  chronic carriers, especially those who
  are “e” antigen positive
 Hepatitis B surface antibody likely
  confers lifelong immunity
 Hepatitis B e Ab indicates low
Hepatitis B - Clinical Features

• Incubation period:                   Average 60-90 days
                                       Range 45-180 days
• Clinical illness (jaundice):         <5 yrs, <10%
                                        5 yrs, 30%-50%
                                        1/3 adults-no
                symptoms
• Acute case-fatality rate:             0.5%-1%
• Chronic infection:                    <5 yrs, 30%-90%
                                         5 yrs, 2%-10%
              •         More likely in asymptomatic infections
• Premature mortality from
  chronic liver disease:          15%-25%
Hepatitis B Clinical Features
   Incubation Period: 6 weeks to 6 months (av.
    120 days)

   Preicteric or Prodromal phase from initial
    symptoms to onset of jaundice usually lasts
    from 3 to 10 days: Non-specific, insidious
    onset of malaise, anorexia, n/v, RUQ
    pain, fever, headache, myalgias, skin
    rashes, arthralgias, arthritis, and dark urine
    beginning 1-2 days before onset of jaundice.
Hepatitis B Clinical Features

   Icteric phase usually lasts from 1-3 weeks:
    jaundice, light or gray stools, hepatic
    tenderness, hepatomegaly.

   Convalescence phase may persist for weeks or
    months: Malaise, fatigue.
    Jaundice, anorexia, and other symptoms
    disappear.
Hepatitis B Symptoms

   About 50%-60% of adults with HBV infection have no
    signs or symptoms.

   Those who do have symptoms might experience:
      Jaundice
      Fatigue
      Abdominal pain
      Loss of appetite
      Nausea, vomiting
      Joint pain
Outcome of Hepatitis B Virus Infection
              100        by Age at Infection                                   100




                                                                                 Symptomatic Infection (%)
                    80                                                         80
Chronic Infection




                    60                                                         60
                                                  Chronic Infection

                    40                                                         40
(%)




                    20                                                         20

                                 Symptomatic Infection
                    0                                                           0
                         Birth   1-6 months 7-12 months    1-4 years Older Children
                                                                       and Adults
                                          Age at Infection
Possible Outcomes of HBV Infection
                 Acute
               hepatitis B
        95% of infection 3-5% of
        infant-
              Chronic HBV adult-
       acquiredinfection acquired
      infectionsChronic infections
                      12-25% in
                hepatitis
   6-15% in 5   Cirrhosi years
                       5 20-23% in
      years
  Hepatocell        s        5 years
                             Liver
       ular                 failure
Death
   carcinoma      Liver             Death
Acute Hepatitis B Virus Infection with Recovery
                  Typical Serologic Course

                     Symptoms

                 HBeAg              anti-HBe



                                    Total anti-HBc
Titer


         HBsAg                  IgM anti-HBc anti-HBs



         0   4   8   12 16 20 24 28 32 36       52   100
                         Weeks after Exposure
Progression to Chronic Hepatitis B Virus Infection
                    Typical Serologic Course
                Acute                      Chronic
             (6 months)                    (Years)
                            HBeAg                      anti-HBe
                                  HBsAg
                                    Total anti-
                                    HBc
Titer



                           IgM anti-
                           HBc




        0 4 8 1 1 2 2 2 3 3            5             Years
          Weeks 6 0 4 8 2 6
              2 after Exposure         2
INTERPRETATION OF THE HEPATITIS B PANEL

Tests          Results                Interpretation

HBsAg          Negative               Susceptible
Anti-HBc       Negative
Anti-HBs       Negative


HBsAg          Negative               Immune
Anti-HBc       Negative or Positive
Anti-HBs       Positive


HBsAg          Positive
Anti-HBc       Positive               Acute Infection
IgM Anti-HBc   Positive
Anti-HBs       Negative

HBsAg          Positive               Chronic Infection
Anti-HBc       Positive
IgM Anti-HBc   Negative
Anti-HBs       Negative

HBsAg          Negative               Four possible interpretations
Anti-HBc       Positive
Anti-HBs       Negative
Interpretation
                HBsAg negative
                HBcAb positive
                HBsAb negative

1.   May be recovering from acute infection.
2.   May be distantly immune and test is not
     sensitive enough to detect very low level of
     HBsAb in serum.
3.   May be susceptible with a false positive
     HBcAb.
4.   May be undetectable level of HBsAg present
     in the serum and the person is actually a
     carrier.
Current Treatment Options for HBV
   Pegylated Interferon alfa (Intron A)

   Lamivudine (Epivir HBV)

   Adefovir dipivoxil (Hepsera)
Elimination of Hepatitis B Virus
          Transmission United States
                     Strategy
•   Prevent perinatal HBV transmission
•   Routine vaccination of all infants
•   Vaccination of children in high-risk groups
•   Vaccination of adolescents
    – all unvaccinated children at 11-12 years of
      age
    – “high-risk” adolescents at all ages
Hepatitis B Vaccine
   Infants: several options that depend on
    status of the mother
    – If mother HepBsAg negative: birth, 1-2m,6-
      18m
    – If mother HepBsAg positive: vaccine and
      Hep B immune globulin within 12 hours of
      birth, 1-2m, <6m
   Adults
    – 0, 1, 6 months
   Vaccine recommended in
    – All those aged 0-18
    – Those at high risk
Hepatitis B High Risk Groups
   Persons with multiple sex partners or diagnosis of a
    sexually transmitted disease
   Men who have sex with men
   Sex contacts of infected persons
   Injection drug users
   Household contacts of chronically infected persons
   Infants born to infected mothers
   Infants/children of immigrants from areas with high
    rates of HBV infection
   Health care and public safety workers
   Hemodialysis patients
Estimated Incidence of Acute Hepatitis B
       United States, 1978-1995
     80                                 HBsAg
                                      screening     Infant
                     Vaccine         of pregnant immunization
     70              licensed          women     recommende
                                   recommended         d
     60
                                                  OSHA Rule
     50                                            enacted
Population
Cases per




                                                             Adolescent
100,000




     40                                                     immunization
                                                            recommende
                                                                 d
     30

     20

                                                                   *
                                 Decline
                                 among        Decline
     10                                       among
                               homosexual
                                  men &      injecting
      0                           HCWs      drug users
          78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95

* Provisional date                 Year
Hepatitis B: Passive Immunization

 Infants of surface antigen positive
  mothers
 Exposures to infected blood or
  infected body fluids in individuals
  who are unvaccinated, unknown
  vaccination, or known non-
  responders.
  – Ideally within 24 hours
  – Probably not effective >7days post
    exposure
Hepatitis B Surveillance

   Acute Hepatitis B is an urgently
    reportable condition. It must be
    reported by phone to DHEC within 24
    hours.

   Chronic Hepatitis B is a reportable
    condition and must be reported to
    DHEC within 7 days.

   Perinatal Hepatitis B is a reportable
    condition and must be reported to
Hepatitis B Surveillance

 Acute,chronic, and perinatal
 hepatitis B must be reported to CDC.

 CDC and S.C. conducts enhanced
 surveillance on acute and perinatal
 hepatitis B cases.
Hepatitis D (Delta) Virus
antigen        HBsAg




               RNA
Hepatitis D Structure
 Defective virus that requires co-
 infection with hepatitis B for
 replication

 Enveloped   with SS RNA genome

 Onlyantigen encoded in the delta
 antigen
Hepatitis D virus genome
Hepatitis D Virus
   Modes of Transmission

• Percutaneous exposures
   – injecting drug use

• Permucosal exposures
   – sex contact
Geographic Distribution of HDV Infection




                                         Taiwan
                                          Pacific Islands


HDV Prevalence
     High
     Intermediat
     e
     Low
     Very Low
     No Data
Hepatitis D:Pathogenesis
 Pathogenesis
  – Immune mediated
  – Co-infection- infection with B at the
    same time (more severe)
  – Superinfection: acquisition of Hep D in
    chronically Hep B
Sequelae of Hepatitis D virus
Hepatitis D - Clinical Features

• Coinfection
  –severe acute disease
  –low risk of chronic infection
• Superinfection
  –usually develop chronic HDV infection
  –high risk of severe chronic liver
   disease
HBV - HDV Coinfection
         Typical Serologic Course
           Symptoms

          ALT Elevated




                                    anti-
Titer




           IgM anti-                HBs
           HDV
         HDV
         RNA
           HBs
           Ag                 Total
                              anti-HDV
                 Time after
                 Exposure
HBV - HDV Superinfection
          Typical Serologic Course
          Jaundice

              Symptoms

                                   Total anti-HDV
                ALT
Titer




                         HDV RNA
               HBsAg


                                   IgM anti-HDV

               Time after
               Exposure
Hepatitis C Virus
Hepatitis D - Prevention
• HBV-HDV Coinfection
   Pre or postexposure prophylaxis to prevent HBV
     infection
• HBV-HDV Superinfection
   Education to reduce risk behaviors among persons with
    chronic HBV infection
• Alpha interferon may help reduce hepatocellular
  damage
Hepatitis C viruses particles and
            genome
Hepatitis C Structure and
         Classification
 Member  of the flavivirus family
  (other members yellow fever and
  dengue)
 Enveloped single stranded RNA virus
 Humans and chimpanzees only
  known reservoirs
 6 serotypes (genotypes) and multiple
  subtypes based on high variability of
  envelope glycoproteins
Hepatitis C Virus Infection, United States
 New infections per year 1985-89     242,000
                        2001         25,000
 Deaths from acute liver failure     Rare
 Persons ever infected (1.8%)        3.9 million
 (3.1-4.8)*
 Persons with chronic infection      2.7 million
 (2.4-3.0)*
 HCV-related chronic liver disease   40% - 60%
 Deaths from chronic disease/year    8,000-10,000
 *95% Confidence Interval
Estimated Incidence of Acute HCV
                                     Infection
                             United States, 1960-2001
                         140
New Infections/100,000




                         120
                         100                                       Decline in injection
                          80                                           drug users
                          60
                          40                          Decline in
                                                transfusion recipients
                          20
                           0
                           1960 1965 1970 1975 1980 1985 1989 1992 1995 1998 2001
                                                       Year
     Source: Hepatology 2000;31:777-82; Hepatology 1997;26:62S-65S;
     CDC, unpublished data
Exposures Known to Be Associated With
   HCV Infection in the United States

 Injecting drug use
 Transfusion, transplant from infected
  donor
 Occupational exposure to blood
    – Mostly needle sticks
 Iatrogenic (unsafe injections)
 Birth to HCV-infected mother

 Sex with infected partner
    – Multiple sex partners
Sources of Infection for
         Persons With Hepatitis C
 Injecting drug use 60%                Sexual 15%
                                                       Transfusion 10%
                                                       (before screening)

                                                        Occupational 4%

                                                        Other 1%*

                                                     Unknown 10%


 * Nosocomial; iatrogenic; perinatal
Source: Centers for Disease Control and Prevention
Posttransfusion Hepatitis C
                            30     All volunteer donors
                                             HBsAg
 % of Recipients Infected




                            25

                            20
                            15                             Donor Screening for HIV Risk Factors
                                                                       Anti-HIV
                            10                                              ALT/Anti-HBc
                                                                                Anti-HCV
                            5                                                               Improved
                                                                                            HCV Tests
                            0
                            1965        1970        1975   1980          1985    1990      1995         2000
                                                                  Year
Adapted from HJ Alter and Tobler and Busch, Clin Chem 1997
Injecting Drug Use and HCV
          Transmission
 Highly   efficient
  – Contamination of drug
    paraphernalia, not just needles and
    syringes
 Rapidly   acquired after initiation
  – 30% prevalence after 3 years
  – >50% after 5 years
 Four   times more common than HIV
Occupational Transmission of
           HCV
 Inefficient by occupational exposures
 Average incidence 1.8% following
  needle stick from HCV-positive source
    – Associated with hollow-bore needles
 Case reports of transmission from blood
  splash to eye; one from exposure to
  non-intact skin
 Prevalence 1-2% among health care
  workers
    – Lower than adults in the general population
    – 10 times lower than for HBV infection
Perinatal Transmission of HCV

   Transmission only from women HCV-
    RNA positive at delivery
    – Average rate of infection 6%
    – Higher (17%) if woman co-infected with
      HIV
    – Role of viral titer unclear
   No association with
    – Delivery method
    – Breastfeeding
   Infected infants do well
    – Severe hepatitis is rare
Sexual Transmission of HCV
   Occurs, but efficiency is low
    – Rare between long-term steady partners
    – Factors that facilitate transmission between
      partners unknown (e.g., viral titer)
   Accounts for 15-20% of acute and
    chronic infections in the United States
    Partner studies
    – Low prevalence (1.5%) among long-term
      partners
        infections
                 might be due to common percutaneous
        exposures (e.g., drug use), BUT
    – Male to female transmission more efficient
        more   indicative of sexual transmission
Household Transmission of HCV

 Rare  but not absent
 Could occur through
  percutaneous/mucosal exposures
  to blood
  – Contaminated equipment used for
    home therapies
     IV   therapy, injections
  – Theoretically through sharing of
    contaminated personal articles
    (razors, toothbrushes)
Other Potential Exposures to Blood
   No or insufficient data showing
    increased risk
    – intranasal cocaine use, tattooing, body
      piercing, acupuncture, military service
   No associations in acute case-control or
    population-based studies
   Cross-sectional studies in highly
    selected groups with inconsistent results
    – Temporal relationship between exposure
      and infection usually unknown
    – Biologically plausible, but association or
      causal relationship not established
Hep C: Pathogenesis
 Blood-borne pathogen that infects
  hepatocytes
 Much like Hep A and B, liver damage
  and clinical illness due more to elicited
  immune response as opposed to direct
  cytopathic effect of the virus
 Likely cytotoxic T cells that mediate
  most of the damage
 Like other chronic liver diseases (Hep B
  and chronic alcoholism), can cause
  hepatocellular ca (HCC)
 Some genotypes more amenable to
  therapy- i.e. 3a
Features of Hepatitis C Virus Infection
Incubation period                Average 6-7 weeks
                                 Range 2-26 weeks
Acute illness (jaundice)         Mild (<20%)
Case fatality rate               Low
Chronic infection                60%-85%
Chronic hepatitis                10%-70% (most
  asx)                  Age-
Cirrhosis              related   <5%-20%
Mortality from CLD               1%-5%
Hepatitis C: Clinical Features
 Acuteinfection asymptomatic in over
 80% of patients, when present,
 acute illness usually mild
  – Acute symptoms include jaundice,
    nausea, abdominal pain, loss of
    appetite, dark urine
Hepatitis C: Extrahepatic Manifestations

  Seen with chronic infection
  ? Due to immune complexes

  Extrahepatic manifestations
     – Essential mixed cryoglobulinemia
       (vasculitis, skin rash, fatigue)
     – Porphyria cutanea tarda
     – Membranoproliferative glomerulonephritis
     – ?Diabetes mellitus
     – Other autoimmune disease
     – ?Lymphoma
Porphyria cutanea tarda
Chronic Hepatitis C
 Factors Promoting Progression or
             Severity
 Increased   alcohol intake
 Age   > 40 years at time of infection
 HIV   co-infection
 Other
  – Male gender
  – Chronic HBV co-infection
Serologic Pattern of Acute HCV Infection
               with Recovery
                                 anti-
         Symptoms +/-            HCV
              HCV RNA
Titer




                         ALT

                   Norm
        0 1 2 3 al 5 6 1 2 3 4
                   4
             Mont                   Year
                Time after Exposure
             hs                     s
Serologic Pattern of Acute HCV Infection with
      Progression to Chronic Infection
                                   anti-
           Symptoms +/-            HCV
                  HCV RNA
  Titer




                                        ALT

                         Norm
          0 1 2 3 4 al 6 1 2 3 4
                         5
               Mont                   Year
                  Time after Exposure
               hs                     s
Hepatitis C: Diagnosis
   ELISA-a serological test which is usually.
    positive within 2-5 months after infection
    – 3rd generation assays now 99% specific and
      sensitive
   Confirmatory testing
    – PCR (positive 1-2 weeks post infection) both
      quantitative and qualitative (I.e. ye/no)
      available
    – RIBA (recombinant immunoblot assay)- looks
      for 2 or more antibodies to HCV viral antigens
   Genotype testing done when treatment
    anticipated
HCV Testing Routinely Recommended

Based on increased risk for infection
 Ever injected illegal drugs
 Received clotting factors made before
  1987
 Received blood/organs before July 1992
 Ever on chronic hemodialysis
 Evidence of for exposure management
Based on need liver disease

 Healthcare, emergency, public safety
  workers after needle stick/mucosal
  exposures to HCV-positive blood
 Children born to HCV-positive women
HCV Infection Testing Algorithm
  for Diagnosis of Asymptomatic Persons
                          Screening Test for                      Negative
                                                                                STOP
                              Anti-HCV
                                      Positive

                                            OR
          RIBA for                         Negative           NAT for HCV
          Anti-HCV                                               RNA
       Negative              Indeterminate            Positive       Positive

               Additional Laboratory              Medical
   STOP       Evaluation (e.g. PCR, ALT)         Evaluation
           Negative PCR, Positive PCR,
            Normal ALT Abnormal ALT


Source: MMWR 1998;47 (No. RR 19)
Medical Evaluation and Management
     for Chronic HCV Infection

 Assess for biochemical evidence of CLD
 Assess for severity of disease and
  possible treatment, according to current
  practice guidelines
    – 40-50% sustained response to antiviral
      combination therapy (peg
      interferon, ribavirin)
    – Vaccinate against hepatitis A
   Counsel to reduce further harm to liver
    – Limit or abstain from alcohol
Hepatitis C Therapy
 Standard of care is pegylated
 interferon alpha and ribavirin

 Many  barriers to treatment as the
 above regimen is difficult to take
 and has many systemic side
 effects
 (fatigue, myalgias, depression, ane
 mia to name a few)

 Overall   response rate to treatment
Postexposure Management for HCV

   IG, antivirals not recommended for
    prophylaxis
   Follow-up after needlesticks, sharps, or
    mucosal exposures to HCV-positive blood
    – Test source for anti-HCV
    – Test worker if source anti-HCV positive
        Anti-HCV  and ALT at baseline and 4-6 months later
        For earlier diagnosis, HCV RNA at 4-6 weeks
    – Confirm all anti-HCV results with RIBA
   Refer infected worker to specialist for
    medical evaluation and management
Hepatitis E Virus
Hepatitis E
 Non-enveloped   single stranded RNA
 virus

 Resembles   calicivirus or Norwalk
 agent

 Similarillness to Hep A except high
 mortality in pregnant women
Geographic Distribution of Hepatitis E
Outbreaks or Confirmed Infection in >25% of Sporadic Non-ABC
                          Hepatitis
Hepatitis E -
     Epidemiologic Features

• Most outbreaks associated with
  fecally contaminated drinking water
• Minimal person-to-person
  transmission
• U.S. cases usually have history of
  travel
  to HEV-endemic areas
Hepatitis E - Clinical Features

• Incubation period:    Average 40 days
                        Range 15-60 days
• Case-fatality rate:   Overall, 1%-3%
                        Pregnant women,
  15%-25%
• Illness severity:     Increased with age
• Chronic sequelae:     None identified
Hepatitis E Virus Infection
               Typical Serologic Course
                         Symptoms


                            ALT
                                          IgG anti-
                                          HEV
                                    IgM anti-
Titer




                                    HEV
          Virus in
          stool


        0 1 2 3 4 5 6 7 8 9 1 1 1 1
               Weeks after Exposure 0 1 2 3
Prevention and Control Measures
  for Travelers to HEV-Endemic
             Regions
• Avoid drinking water (and beverages with ice) of
  unknown purity, uncooked shellfish, and uncooked
  fruit/vegetables not peeled or prepared by traveler
• IG prepared from donors in Western countries
  does not prevent infection
• Unknown efficacy of IG prepared from donors in
  endemic areas
• Vaccine?
INFLUENZA
  VIRUS
„FLU‟
 True   influenza
  – influenza virus A or influenza virus B (or
    influenza virus C infections - much
    milder)


 Febrilerespiratory disease with
 systemic symptoms caused by a
 variety of other organisms often
 inaccurately called „flu‟
South Carolina 1996-1997 DHEC bulletin
      malathia influenzae per le stel


                                               no virus


      CULTURE
      RESULTS
                                                 influenza A

                                                 influenza B



http://www.state.sc.us/dhec/LAB/labbu017.htm
THE IMPACT OF INFLUENZA
        PANDEMICS
Deaths:

  1918-19 Spanish flu 500,000 US
                      20,000,000 world
  1957-58 Asian flu   70,000 US
THE IMPACT OF INFLUENZA
  In   the United States, on average:

  36,000   deaths per year

  114,000    hospitalizations per year




CDC: MMWR 53:8-11, 2004
THE IMPACT OF INFLUENZA
 recently
        some increase in morbidity
 and mortality - possible factors?
  – more elderly people
  – CF patients live longer
  – more high risk neonates
  – more immunosuppressed patients
ORTHOMYXOVIRUSES

pleomorphic
influenza types A,B,C
febrile, respiratory
  illness with
  systemic symptoms


                        http://www.uct.ac.za/depts/mmi/stannard/fluvirus.ht
ORTHOMYXOVIRUSES
                      HA - hemagglutinin

                             NA - neuraminidase


                          helical nucleocapsid (RNA plu
                          NP protein)

                             lipid bilayer membrane

                             polymerase complex



                          M1 protein

type A, B, C : NP, M1 protein
sub-types: HA or NA protein
TRANSMISSION
   AEROSOL
    – 100,000 TO
      1,000,000
      VIRIONS PER
      DROPLET


   18-72 HR
    INCUBATION

   SHEDDING
NORMAL TRACHEAL MUCOSA




       3 DAYS POST-INFECTION                         7 DAYS POST-INFECTION
Lycke and Norrby Textbook of Medical Virology 1983
   DECREASED
    CLEARANCE

   RISK BACTERIAL
    INFECTION

   VIREMIA RARE



                     Lycke and Norrby Textbook of Medical Virology 1983
RECOVERY

 INTERFERON   - SIDE EFFECTS
 INCLUDE:
 – FEVER, MYALGIA, FATIGUE, MALAISE

 CELL-MEDIATED     IMMUNE RESPONSE

 TISSUE   REPAIR
 – CAN TAKE SOME TIME
An immunological
    diversion
   INTERFERON
INTERFERON




timecourse of virus production will vary fro
INTERFERON
INTERFERON


                     antiviral state




antiviral state                        antiviral state




                     antiviral state
INTERFERON


                     antiviral state




antiviral state                        antiviral state




                     antiviral state
INTERFERON


                     antiviral state




antiviral state                        antiviral state




                     antiviral state
INTERFERON
THE VIRUSES ARE COMIN




                               PAUL REVERE
                               http://www.mfa.org/collections/one_hour/6.htm


  http://www.paulreverehouse.org/midnight.html
TYPES OF INTERFERON

TYPE I
 Interferon-alpha (leukocyte
 interferon, about 20 related
 proteins)
      - leukocytes, etc
 Interferon-beta (fibroblast
 interferon)
      - fibroblasts, epithelial cells,
      etc
INDUCTION OF INTERFERON

interferon-alpha and interferon-
beta
  - viral infection (especially RNA
  viruses), double stranded RNA,
  certain bacterial components
  - strong anti-viral properties
interferon-gamma
  - antigens, mitogenic stimulation
  lymphocytes
INTERFERON
 induces   variety of proteins in target
 cells

 manyconsequences, not all fully
 understood
INTERFERON-ALPHA AND
   INTERFERON-BETA
interferon-alpha, interferon-beta


                            interferon receptor



    induction of         induction of                  induction of
2’5’oligo A synthase   ribonuclease L             protein kinase R (PKR)

 ds RNA            2’5’oligo A                      ds RNA

      activated           activated                     activated
2’5’oligo A synthase   ribonuclease L                protein kinase R

            ATP                                                ATP


                                                phosphorylated
    2’5’oligo A
                                             initiation factor (eIF-
                                                        2)


                       mRNA degraded     inhibition of protein synthesi
interferons
 only   made when needed
OTHER EFFECTS OF
          INTERFERONS

 ALL   TYPES
  – INCREASE MHC I EXPRESSION
     CYTOTOXIC   T-CELLS
  – ACTIVATE NK CELLS
     CAN   KILL VIRALLY INFECTED CELLS
OTHER EFFECTS OF
     INTERFERONS
 INTERFERON-GAMMA
 – INCREASES MHC II EXPRESSION ON
   APC
    HELPER   T-CELLS
 – INCREASES ANTIVIRAL POTENTIAL OF
   MACROPHAGES
    INTRINSIC

    EXTRINSIC
THERAPEUTIC USES OF
         INTERFERONS
   ANTI-VIRAL
    – e.g. interferon-alpha is currently approved for
      certain cases of acute and chronic HCV and
      chronic HBV
   MACROPHAGE ACTIVATION
    – interferon-gamma has been tried for e.g.
      lepromatous leprosy, leishmaniasis,
      toxoplasmosis
   ANTI-TUMOR
    – have been used in e.g. melanoma, Kaposi‟s
      sarcoma, CML
   MULTIPLE SCLEROSIS
Viral response to host immune
            system
Viruses may :
  block interferon binding
  inhibit function of interferon-induced
  proteins
  inhibit NK function
  interfere with MHC I or MHC II expression
  block complement activation
  inhibit apoptosis
  etc!
SIDE EFFECTS OF
        INTERFERONS

 FEVER

 MALAISE

 FATIGUE

 MUSCLE    PAINS
BACK TO INFLUENZA
PROTECTION AGAINST
       RE-INFECTION

 IgG   and IgA
  – IgG less efficient but lasts longer


 antibodies   to both HA and NA
 important
  – antibody to HA more important (can
    neutralize)
SYMPTOMS
 FEVER

 HEADACHE

 MYALGIA

 COUGH

 RHINITIS

 OCULAR   SYMPTOMS
CLINICAL FINDINGS

   SEVERITY
    – VERY YOUNG
    – ELDERLY
    – IMMUNO-
      COMPROMISED
    – HEART OR LUNG
      DISEASE
PULMONARY
       COMPLICATIONS
 CROUP (YOUNG CHILDREN)
 PRIMARY INFLUENZA VIRUS
  PNEUMONIA
 SECONDARY BACTERIAL INFECTION
 – Streptococcus pneumoniae
 – Staphlyococcus aureus
 – Hemophilus influenzae
NON-PULMONARY
          COMPLICATIONS
 myositis (rare, > in children, > with type
  B)
 cardiac complications
 recent studies report encephalopathy
    – 2002/2003 season studies of patients younger
      than 21 yrs in Michigan - 8 cases (2 deaths)
   liver and CNS
    – Reye‟s syndrome
   peripheral nervous system
    – Guillian-Barré syndrome
Reye‟s syndrome
 liver - fatty deposits
 brain - edema

 vomiting, lethargy, coma

 risk factors
  – youth
  – certain viral infections (influenza,
    chicken pox)
  – aspirin
Guillian-Barré syndrome
 1976/77     swine flu vaccine
 – 35,000,000 doses
    354  cases of GBS
      28 GBS-associated deaths

    recent   vaccines much lower risk
MORTALITY

 MAJORCAUSES OF INFLUENZA
 VIRUS- ASSOCIATED DEATH
 – BACTERIAL PNEUMONIA
 – CARDIAC FAILURE


 90%OF DEATHS IN THOSE OVER 65
 YEARS OF AGE
DIAGNOSIS
 ISOLATION
  – NOSE, THROAT SWAB
  – TISSUE CULTURE OR EGGS
 SEROLOGY

 PCR

 RAPID  TESTS
 provisional - clinical picture +
  outbreak
ANTIGENIC DRIFT
 HA   and NA accumulate mutations
  – RNA virus


 immune     response no longer protects
 fully

 sporadic
         outbreaks, limited
 epidemics
ANTIGENIC SHIFT
 “new”   HA or NA proteins

 pre-existing   antibodies do not
 protect

 may   get pandemics
INFLUENZA A PANDEMICS




Ryan et al., in Sherris Medical
Microbiology
where do “new” HA and NA
           come from?
13 types HA
 9 types NA
    – all circulate in
      birds
   pigs
    – avian and human
Where do “new” HA and NA come from?
Where do “new” HA and NA come from
- can „new‟ bird flu directly infect humans?

                  Bird flu H5N1?
why do we not have influenza B
        pandemics?
 so far no
  shifts have
  been
  recorded
 no animal
  reservoir
  known
SURVEILLANCE




CDC/Katherine Lord
actual percentage of deaths




(CDC MMWR July 1, 2005 / 54(25);631-634)
% typed cases
100
 90
 80
 70
 60                                     H1N1
 50
                                        H3N2
 40
                                        B
 30
 20
 10
  0
      00/01   01/02 02/03 03/04 04/05
                  influenza
VACCINE
 „BEST   GUESS‟ OF MAIN ANTIGENIC
 TYPES
  – CURRENTLY
     type A - H1N1
     type A - H3N2

     type B

     each year choose which variant of each
      subtype is the best to use for optimal
      protection
VACCINE
 inactivated
 egg  grown
 some formulations licensed for
  children

 reassortant   live vaccine approved
 2003
  – for healthy persons (those not at risk
    for complications from influenza
    infection) ages 5-49 years
CDC
OTHER TREATMENT
 REST,
      LIQUIDS, ANTI-FEBRILE
 AGENTS (NO ASPIRIN FOR AGES
 6MTHS-18YRS)

 BEAWARE OF COMPLICATIONS AND
 TREAT APPROPRIATELY
VIRAL AGENTS
    CAUSING
GASTROENTERITIS
VIRAL AGENTS CAUSING
   GASTROENTERITIS

1. Rotavirus
2. Enteric adenoviruses
3. Calicivirus
4. Astrovirus
ROTAVIRUS

Family Reoviridae

Genus Rotavirus
ROTAVIRUS
 First   isolated in 1973 from children
 with diarrhea
 EM   identification from duodenal
 biopsies
 Human     and animal strains
ROTAVIRUS STRUCTURE
ROTAVIRUS - STRUCTURE
STRUCTURAL FEATURES OF
          ROTAVIRUS

   60-80nm in size
   Non-enveloped virus
   EM appearance of a wheel with radiating
    spokes
   Icosahedral symmetry
   Double capsid
   Double stranded (ds) RNA in 11 segments
STRUCTURE
   Double capsid (outer and inner
capsid)

   Core with genome

   Capsid is cleaved by trypsin to
form

   ISVP- infective sub-viral particle
ROTAVIRUS- 3D STRUCTURE
ROTAVIRUS- ultrastructure
ROTAVIRUS
EM STRUCTURE
VIRAL STRUCTURAL PROTEINS
           (VP)

    Outer structural proteins - VP7 and VP4
            VP7 - Glycoprotein

     VP4 - protease-cleaved, P protein, viral
     hemagglutinin; forms spikes from the surface

    Inner core structural proteins VP 1, 2,
     3, 6

    VP6 is an important antigenic
STRUCTURE
CLASSIFICATION


   Groups- 7 Groups (A through G) based on VP6
     differences

    Group A is the most common and has 2
subgroups
CLASSIFICATION (contd.)
 Serotypes   based on viral capsid proteins

 14   G serotypes based on G protein (VP 7)
 differences

 20   P serotypes based on P protein (VP4)

 Common     PG combinations are:-

 P8G1, P8G2, P4G2, P8G4
CLASSIFICATION (contd.)


   Electropherotypes are based on the mobility of

    RNA segments by PAGE

   Useful in epidemiologic studies
ROTAVIRUS- PROPERTIES

   Virus is stable in the environment
   Relatively resistant to handwashing
    agents
   Susceptible to disinfection with 95%
    ethanol, „Lysol‟, formalin
PATHOGENESIS

   Targeted host cells - mature enterocytes
    lining the tips of intestinal villi
   Intermediate/infective sub-viral particle
    (ISVP) produced through proteolysis
   Enter host cell by endocytosis
   Virus replicates in the host cell cytoplasm
REPLICATION
   mRNA transcription with viral RNA
    polymerase
   Capsid proteins formed
   mRNA segments formed, assembled into
    immature capsid
   mRNA replicated to form double stranded
    RNA genome
HISTOPATHOLOGY

 Mature    enterocytes lining the tips of
 intestinal villi are affected

 Villous   atrophy and blunting

 Death     of the mature enterocytes
HISTOPATHOLOGY

 Infiltration   of lamina propria with
 mononuclear cells

 Repopulation     of the villous tips with
 immature secretory cells [crypt
 hyperplasia]
HISTOPATHOLOGY
EPIDEMIOLOGY

A   major cause of diarrhea-
 associated hospitalizations and
 deaths

 Seroprevalence   studies show that
 antibody is present in most by age
 3y.
ROTAVIRAL DISEASE
   BURDEN- World
WORLDWIDE DISTRIBUTION OF
      ROTAVIRUS
   (Source- Centers for Disease Control and Prevention)
EPIDEMIOLOGY - USA
   2.7- 3.5 million affected each year
   Physician visits ~ 500,000/year

   50,000-70,000 hospitalizations/year

   20-40 deaths/year

   Cases with dehydration ~ 1-2.5%

   Economic impact
EPIDEMIOLOGY
   Age- 4mo - 2 years
    Protection of younger infants through
    through transplacental antibody transfer
   Asymptomatic infections are common,
    especially in adults
   Nosocomial infections
   Outbreaks
   Severe Disease young,
    immunocompromised
Epidemiology (contd.)

 Seasonality

 Winter months (Nov. through May in US)
 Gradual spread W to E
 Year-round in the tropics

 Incubation    period   - thought to be <4
 days
EPIDEMIOLOGY
(Source- Centers for Disease Control and Prevention)
SEASONAL SPREAD - U.S.
        (Source- CDC)
TRANSMISSION

 Mainly   person to person via fecal-oral
 route
 Fomites

 Foodand water-borne spread is
 possible
 Spreadvia respiratory route is
 speculated
EPIDEMIOLOGY -
                  spread

   Contagious from before onset of diarrhea
    to a few days after end of diarrhea
   Large amounts of viral particles are shed
    in diarrheal stools
   Infective dose is only 10-100 pfu
EPIDEMIOLOGY
           Differences in Groups


   Group A infections are most common
   Group B has been associated with
    outbreaks in adults in China
   Group C is responsible for sporadic
    cases of diarrhea in infants around
    the world
CLINICAL CASE
   A 22 month old female is admitted to the
    pediatric ward for cough and fever up to 103 F.
   Chest X ray shows left lower lobe pneumonia.
   She is being treated with intravenous Ceftriaxone
    and her fever is gradually improving.
   On hospital day #5, she develops diarrhea with 4
    watery stools and a fever of 102 F.
   Stool studies showed no traces of blood and no
    fecal leukocytes.
   Further studies are pending.
CLINICAL FEATURES
   Incubation period - thought to be <4 days
   Fever- can be high grade (>102 F in 30%)
   Vomiting, nausea precede diarrhea
   Diarrhea
    • usually watery (no blood or leukocytes)
    • lasts 3-9 days
    • longer in malnourished and immune deficient individuals.
    • NEC and hemorrhagic GE seen in neonates
MECHANISM OF DIARRHEA

   Watery diarrhea due to net secretion of
    intestinal fluid
   Activation of the enteric nervous system
   Role of NSP4 peptide regions as an
    enterotoxin
CLINICAL FEATURES
                (contd.)

 Dehydration  is the main
  contributor to mortality.
 Secondary malabsorption of
  lactose and fat, and chronic
  diarrhea are possible
DIAGNOSIS
   Antigen detection in stool by ELISA, LA
    (for Group A rotavirus)
   EM- non-Group A viruses also
   Culture- Group A rotaviruses can be
    cultured in monkey kidney cells
   Serology for epidemiologic studies
TREATMENT AND
          PREVENTION
   Treatment
    Supportive- oral, IV rehydration
   Prevention
    Handwashing and disinfection of
    surfaces
VACCINE
   Live tetravalent rhesus-human reassortant
    vaccine (Rotashield)
   Licensed for use in August 1998
   Removed from the market in October 1999
    due to risk of intussusception
   Cases were seen 3-20 days after
    vaccination
   Approx. 15 cases/1.5 million doses
NEWER VACCINES
          Rotarix                      Rota Teq
   Monovalent G1P8 oral         Pentavalent Human-
    vaccine                       bovine reassortant
                                  vaccine
   Efficacy for prevention      Efficacy for prevention
    of severe disease =           of severe disease =
    85%                           100%
GASTROENTERITIS DUE
TO ENTERIC ADENOVIRUS
GASTROENTERITIS DUE TO
     ADENOVIRUS
  Types   40, 41
  Belong   to serogroup F
Diarrhea due to
Enteric Adenovirus
   Age <4 years
   Year round
   Spread via fecal-oral route
CLINICAL FEATURES-
       Adenovirus gastroenteritis

   Incubation period 3 -10 days
   Diarrhea lasts for 10 -14 days
   Can also cause intussusception,
    mesenteric adenitis, appendicitis
DIAGNOSIS
       Enteric adenoviruses

 Isolation
        requires special media-
 Graham 293

 ELISA for rapid detection is
 available
HUMAN
CALICIVIRUSES
HUMAN CALICIVIRUSES
      (HuCV)
•   Family Caliciviridae
•   Non-enveloped RNA viruses
    with ss RNA
•   27-35 nm in size
•   Contain a single capsid protein
HUMAN CALICIVIRUSES

 Genomic analysis divides it into 4
groups
Human caliciviruses belong to 2
genera
CLASSIFICATION OF HuCV
NLV (Norovirus)       SLV (Sapovirus)
Norwalk virus           Sapporo virus
Hawaii virus            Manchester virus
Snow Mountain virus     Houston/86
Montgomery county       London/92
virus
Taunton (England)
MORPHOLOGY- typical

• 32 cup-like depressions
• EM appearance of “Star of
David”
• 31-35 nm size
• E.g.- Sapporo-like viruses
HUMAN CALICIVIRUSES - SLV
Morphology of HuCV-
     atypical
• Smaller size- approx. 27 nm
• Rough, feathery surface but
no        internal pattern
• Small Round Structured
viruses
• E.g.- Norwalk-like viruses
SRSV- NORWALK VIRUS
CLINICAL FEATURES

 Usual   incubation Period is <24
 hours
    (ranges from 12hrs. to 4 days)
 Short   duration of illness <3 days
 Nausea,   vomiting, fever, headache
 Abdominal    cramping
 Watery   diarrhea
EPIDEMIOLOGY - Noroviruses
 Worldwide    distribution
 >23    million cases/year in the U.S.
 Major   cause of foodborne
 outbreaks of GE (>50%)
 Most   people have had infections by
 age 4 years (by seroprevalence
 studies)
SPREAD

   Person-to-person Fecal-oral
    spread (stool/vomitus)
   Fecal contamination of food or
    water
   Spread through fomites
    (stool/vomitus)
SPREAD- Viability of
         Caliciviruses
 Survive in water chlorinated at
 routine levels (up to 10 ppm)
 Survive    freezing, heating up to
 60 C
 Evidently   survive in steamed
 shellfish
EPIDEMIOLOGY
• Asymptomatic infections-
seroconversion but
    asymptomatic shedding of virus
•   Low infective dose (~10 pfu)
• Viral excretion during convalesence (~
2 wk.)
EPIDEMIOLOGY : Outbreaks

 Cruise ships, schools, nursing
    homes,
   Can involve infants and school-age
    children
   Source usually is contaminated food
    and water (E.g. seafood-oyster and
    shellfish, salads, cake icing, raw fruit
    etc.)
   Rapid secondary spread
DIAGNOSIS

   Specimen- stool, vomitus,
    environmental swabs (during outbreak
    investigations)
   RT-PCR in state public health labs.
   Serology for epidemiologic purposes
   Immune EM is less used
HUMAN
ASTROVIRUS
ASTROVIRUS
   Described in relation to an outbreak of
    gastroenteritis in 1975
   Detected by EM
   Immunologically distinct from Human
    Caliciviruses
   Belong to family Astroviridae
   8 human serotypes are known
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  • 2. 1796:Edward Jenner (1749-1823)  used cowpox to vaccinate against smallpox  was the first person to deliberately vaccinate against any infectious disease  used a preparation to elicit an immune response.  Variolation – infecting people with smallpox – to protect them from the worst type of the disease
  • 3. 1885: Louis Pasteur (1822-1895)  experimented with rabies vaccination  using the term "virus" to describe the agent  "virus" and "vaccination" (in honor of Jenner)
  • 4. 1886: John Buist  Scottish pathologist  stained lymph from skin lesions of a smallpox – "elementary bodies" – he thought were the spores of micrococci – smallpox virus particles
  • 5. 1892: Dmiti Iwanowski (1864- 1920)  described the first "filterable" infectious agent – tobacco mosaic virus (TMV)  smaller than any known bacteria  first to discriminate between viruses and other infectious agents
  • 6. 1898: Martinus Beijerinick (1851- 1931) – extended Iwanowski's work with TMV – developed the concept of the virus as a distinct entity
  • 7. Freidrich Loeffler (1852-1915) and Paul Frosch (1860-1928) – demonstrated that foot and mouth disease – first to prove that viruses could infect animals as well as plants
  • 8. 1900: Walter Reed (1851-1902)  demonstrated that yellow fever is spread by mosquitoes  first to show that viruses could be spread by insect vectors such as mosquitoes 1908: Karl Landsteiner (1868- 1943) and Erwin Popper  proved that poliomyelitis: virus  proved that viruses could infect humans as well as animals
  • 9. 1911: Francis Peyton Rous (1879- 1970)  demonstrated that a virus (Rous sarcoma virus) can cause cancer in chickens  first person to show that a virus could cause cancer
  • 10. 1915: Frederick Twort (1877-1950)  discovered viruses infecting bacteria 1917: Felix d'Herelle (1873-1949) – independently discovered viruses of bacteria – coins the term bacteriophage
  • 11. 1938: Max Theiler (1899-1972)  developed a live attenuated vaccine against yellow fever  safe and effective that it is still in use today! 1940: Helmuth Ruska (1908-1973)  used an electron microscope: virus particles  direct visualization of virions
  • 12. 1941: George Hirst  demonstrated that influenza virus agglutinates red blood cells  viruses could be counted 1945: Salvador Luria (1912-1991) and Alfred Hershey (1908-1997)  demonstrated that bacteriophages mutate  antigenic variation in viruses.
  • 13. 1957: Alick Isaacs and Jean Lindemann  discovered interferon – first cytokines to be studied in detail Carleton Gajdusek – proposed: a "slow virus" is responsible for the prion disease kuru – kuru is similar to that of scrapie – kuru can be transmitted to
  • 14. 1961: Sydney Brenner, Francois Jacob, and Matthew Meselson  demonstrated that bacteriophage T4 uses host cell ribosomes – to direct virus protein synthesis – fundamental molecular mechanism of protein translation.
  • 15. 1963: Baruch Blumberg  discovered hepatitis B virus (HBV)  developed the first vaccine against the HBV – first vaccine against cancer 1989: Hepatitis C virus (HCV)  nonA, nonB hepatitis  first infectious agent to be identified by molecular cloning of the genome
  • 16. Sending Specimens to the Laboratory –Right specimen –Taken at the right time –Stored and transported immediately
  • 17. Specimens for viral isolation or Ag detection Respiratory Infection Nasal or throat  swabs, postnasal washings Gastrointestinal infxn Feces Vesicular rash Vesicular fluid, throat swab, feces Hepatitis Serum, feces CNS CSF, throat swab, feces AIDS Unclotted blood
  • 18. SPECIMENS:  Blood serum – syringe – vacutainer  Swabs – skin lesions – throat – transport medium  antibacterial  antifungal
  • 19. Vesicle fluid – tip of a scalpel blade – large needle – spread on a slide  CSF – dry sterile container  Feces – dry sterile container – rectal swab
  • 20. Storage: – secure plastic bags – labeled – transported ASAP – 4oC: overnight  Request forms: – date on onset of disease – clinical signs – suspected diagnosis
  • 21. Laboratory Diagnosis for viral Infections
  • 22. 3 Basic categories of methods used in the Diagnosis of virus infections Direct Examination Indirect examination Serology
  • 23. Direct Examination Clinicalspecimen examined directly for presence of virus particles, virus antigens, viral nucleic acids and virus-induced histological changes
  • 24. Direct Examination Clinical specimen –virus particles –virus antigens –viral nucleic acids –virus-induced histological changes
  • 25. Direct Examination Main advantage: short length of time required for result Results available the same day specific antiviral chemotherapy
  • 26. Direct Examination Automated molecular biology techniques available: 1. PCR-based amplicor system 2. Abbott LCR system 3. Chiron branched DNA system
  • 27. Direct Examination Wave of the future: DNA chip technology  detect viruses from clinical specimens  tell viral load  determine antiviral agent the virus is sensitive to
  • 28. Indirect Examination Virus amplification: growing in tissue culture, eggs or animals Growing virus: changes cytopathic effect (CPE) ability to hemadsorb Identity of virus confirmed by: virus neutralization Immunofluorescence complement fixation electron microscopy
  • 29. Indirect Examination Disadvantage of virus culture: long time required for CPE ability to hemadsorb to become apparent May take a few days to a few weeks Virus culture sensitivity: low and depends on quality of clinical specimen received Not applicable to viruses that are difficult or can not be cultivated
  • 30. SEROLOGY Remains the bulk of work carried out by a routine diagnostic laboratory Complement fixation test hemagglutination-inhibition enzyme linked immunoassay Radioimmunoassay particle agglutination Immunofluorescence single radial hemolysis western blot
  • 31. SEROLOGY Sensitivity and specificity rates vary Most techniques will detect all classes of antibody Some assays like RIA, EIA and IF can be made to detect one specific class IgM, IgG, IgA Virus infections usually diagnosed by serology: * hepatitis A, B and C
  • 32. DIFFICULT VIRUSES Viral infections of the Central nervous system infection in immunocompetent hosts infection caused by HIV and opportunistic infections Viral pneumonias Viral skin infections Emerging viral infections
  • 33. Viral infections of the CNS  Most cases of acute encephalitis in immunocompetent hosts due to: * HSV-1 and HSV-2 * EBV * HHV-6 and HHV-7  Among immunocompromised individuals: * CMV * VZV
  • 34. Viral infections of the CNS Diagnosis revolutionized by availability of cerebrospinal fluid (CSF) polymerase chain reaction analysis PCR allows rapid, specific and sensitive diagnosis
  • 35. Viral infections of the CNS  CSF-PCR instead of brain biopsy – Dx standard for HSV encephalitis – mild or atypical cases 16-25% of cases  HSV PCR analysis of CSF –monitoring adequacy of therapy –14day treatment with acyclovir  negative PCR  Prognosis: – Determination of number of viral DNA copies
  • 36. Viral infections of the CNS  EBV semi-quantitative PCR –significantly higher: active EBV infection – latently infected patients seropositive: LOWER  positive EBV PCR in CSF –sensitive and specific primary CNS lymphoma in patients with AIDS CNS mass lesions
  • 37. Viral infections of the CNS  HHV 6 and HHV 7 –Almost all children –PCR  review of CSF specimens from patients initially suspected to have HSV encephalitis found HHV 6 DNA in ~ 7% of specimens – suggests HHV 6 may be an important cause of sporadic focal encephalitis
  • 38. Viral infections of the CNS  Using CSF RT-PCR analysis –most cases (85-95%) of acute viral meningitis  enteroviruses  Signs and symptoms indicative of encephalitis rather than meningitis develop in ~ 3% of patients  Patients with agammaglobulinemia are at risk for chronic enteroviral meningoencephalitis
  • 39. Viral Pneumonias  Causes in adults: * Adenovirus * Influenza A & B * CMV * Measles * HSV * Parainfluenza virus * RSV * VZV  Causes in children * Influenza A & B * Measles * Parainfluenza * RSV
  • 40. Diagnostic techniques for herpesvirus infections Virus Cytologic Viral Antigen Gene evaluation culture detection ampli- fication HSV Cowdry CPE IFA PCR Type A SVA ELISA bodies VZV Cowdry CPE IFA MRT-PCR Type A bodies CMV “owl’s CPE IFA MRT-PCR eye” cells SVA ELISA
  • 41. Diagnostic techniques for herpesvirus infections Virus Cytologic Viral Antigen Gene evaluation culture detection ampli- fication Highly CPE IFA MRT-PCR RSV eosinophilic intracytoplas SVA ELISA mic inclusions Para Large cells HA IFA MRT-PCR with single influenza nucleus & SVA ELISA multiple small eosinophilic inclusions Measles HA IFA ELISA
  • 42. Diagnostic techniques for viral infections Influenz HA IFA a virus SVA ELISA Adeno Intra- CPE IFA MRT- virus nuclear SVA ELISA PCR inclusions
  • 43. Herpes virus skin infection Diagnosis  Tzanck preparation : –used to rapidly determine presence of HSV or VZV –does not distinguish between these 2 viruses  Stains : Giemsa,Wright’s, methylene blue  Characteristic multinucleated giant cells – inexpensive, efficient provisional diagnosis
  • 44. Herpes virus skin infection Diagnosis  HSV tissue culture: using monoclonal antibodies, requires only 24 hours –sensitive test but expensive  Polymerase chain reaction –expensive  Serology not very useful – general population has antibodies to herpes simplex
  • 45. Emerging Viral Infections  Acute Hemorrhagic fever syndromes: – Ebola and Marburg v – Hantavirus – Arena virus  Other viral encephalitis agents: – Nipah virus (previously unknown paramyxovirus)
  • 46.  Labtesting currently available only at CDC: –antigen detection – IgM antibody detection –isolation in cell culture –visualization by electron microscopy – immunohistochemical techniques –RT-PCR
  • 47. Emerging Viral Infections  Many of these “emerging” viral infections are thought to pose a serious risk as biologic weapons  Rapid diagnostics should be made available worldwide in order to detect as rapidly as possible both justified and unjustified suspects of HF and attacks by other “biological weapons”
  • 48. Emerging Viral Infections  SARS –Severe acute respiratory syndrome –Killer pneumonia  Cause has yet to be identified  Laboratory tests found two types of virus: –paramyxovirus –corona virus  A rapid diagnostic test should come soon
  • 49. SUMMARY Despite enhanced laboratory techniques such as viral culture, rapid antigen detection and gene amplification, a confident diagnosis of viral pneumonia continues to be a CHALLENGE
  • 50. SUMMARY The non-specific nature of clinical characteristics & the extreme sensitivity of lab techniques make the diagnosis difficult, even when a viral agent is detected
  • 51. SUMMARY Understanding the limitations of these technological advances and the use of histopathological techniques can greatly enhance a skilled clinician’s ability to make an accurate diagnosis
  • 53. ADENOVIRUS DNA viruses first isolated from adenoidal tissue in 1953
  • 54. ADENOVIRUS Family Adenoviridae Genus Mastadenovirus
  • 55. Transmission electron micrograph of adenovirus Source- PHIL, CDC
  • 56. ADENOVIRUS - Classification • Subdivided into 6 subgroups based on • hemagglutination (A-F) • Human pathogens belong to 49 serotypes • Common serotypes:- 1-8, 11, 21, 35, 37, 40 • Enteric Adenoviruses belong to subgroup F
  • 57. ADENOVIRUS - Structure  Non-enveloped DNA virus  70-90 nm in size  Linear ds DNA genome with core proteins
  • 59. ADENOVIRUS - Ultrastructure  Icosahedral capsid with 252 capsomeres (12 pentons at vertices and 240 hexons)  Each penton has a fibers with terminal knob projecting from it
  • 60. Adenovirus- 3 D structure
  • 61. Adenovirus - EM appearance Note- projecting fibers and terminal knob
  • 65. Pathogenesis and Replication • Infects mucoepithelial cells of respiratory, GI and GU tracts • Enter via epithelium, replicate and spread to lymphoid tissue • Viremia occurs • Secondary involvement of
  • 66. Pathogenesis and Replication (contd.)  Fiber protein determines target cell specificity and attachment  Viral DNA enters host cell nucleus  Virus replicates in cytoplasm
  • 68. Replication (contd.) • Early and late phases of replication • Errror-prone process • Inclusion bodies in nucleus
  • 70. Types of infection  Lytic  Latent/occult  Oncogenic Transformation
  • 71. Types of infection  Lytic Results in cell death; seen in mucoepithelical cells  Latent/occult Virus remains in host cell; seen in lymphoid tissue, Groups B and C  Oncogenic Transformation Uncontrolled cell growth and replication occur; seen with Group A viruses in hamsters
  • 72. Adenovirus  Used as VECTORS to transfer desired genetic material into cells e  Viral genome is relatively easily manipulated in vitro  Efficient expression of inserted DNA in recipient cell
  • 73. Adenovirus- Properties  Stable in the environment  Relatively resistant to disinfection (Alcohol, chlorhexidine, detergents)  Stable in GI tract- can withstand low pH, bile acids and proteolytic enzymes
  • 74. Time-course of infection  Incubation period- 2-14 days  Infective period continues for weeks  Intermittent and prolonged rectal shedding  Secondary attack rate within families up to 50%
  • 75. Timecourse - Respiratory infection Source- Medical Microbiology- Murray, Rosenthal, Kobayshi and Pfaller
  • 76. EPIDEMIOLOGY Endemic, epidemic and sporadic infections Many infections are subclinical
  • 77. EPIDEMIOLOGY-contd. ”Tip of the iceberg phenomenon” Classical disease presentation Mild clinical disease Asymptomatic infection but infectivity (+)
  • 78. Epidemiology of Adenoviral Infections (source-centers for disease control and prevention)
  • 79. EPIDEMIOLOGY Outbreaks noted in military recruits, swimming pool users, hospitals, residential institutions, day care settings
  • 80. EPIDEMIOLOGY-transmission  Prolonged infective period (weeks)  Intermittent and prolonged rectal shedding  Stable in the environment
  • 81. TRANSMISSION • Droplets • Fecal-oral route • Direct and through poorly chlorinated water • Fomites
  • 82. CLINICAL SYNDROMES • Respiratory • Eye • Genitourinary • Gastrointestinal • Others
  • 83. Acute Respiratory Disease (LRI)  Fever  Tracheobronchitis  Pneumonia  Childrenand adults  Epidemics in military recruits  Types 4 and 7 most frequently
  • 85. Pharyngoconjunctival fever  Headache, fever, malaise  Conjunctivitis and Pharyngitis  Cervical adenopathy, rash and diarrhea also  Main adenovirus types: 3, 4, 7, 14  Epidemics in summer months  Contaminated water in swimming pools, fomites
  • 86. Adenoviral Infections of the eye Epidemic Keratoconjunctivitis (EKC) Acute follicular conjunctivitis Pharyngoconjunctival fever
  • 88. Epidemic Keratoconjunctivitis  Incidence in summer  Conjunctivitis usually followed by keratitis  Headache  Pre-auricular lymphadenopathy  Types 8, 19, 37  Nosocomial spread by fomites, hands, ophthalmologic equipment, medications
  • 89. Gastrointestinal Infections  Types 40, 41  Age <4 years  Spread via fecal-oral route  Year round
  • 90. Gastrointestinal Infections- (contd.)  Incubation period 3-10 days  Diarrhea lasts for 10-14 days  Fever  Also, intussusception, mesenteric adenitis, appendicitis
  • 92. ADENOVIRAL INFECTIONS- Genitourinary system Acute hemorrhagic cystitis  fever, dysuria, hematuria  Types 11, 7, 4, 21, 1  More common in boys Others  Orchitis, nephritis, cervicitis with ulcerated vesicular lesions  Types 2, 19, 37
  • 93. Other Infections due to Adenovirus •Myocarditis •Pericarditis •Meningitis •Rash •Arthritis
  • 94. Adenovirus infections in Immunocompromised hosts  Disseminated, severe and often fatal infections  Due to new infection or reactivation of latent virus  Prolonged infections with prolonged viremia and viral shedding  Necrotizing pneumonia, hepatitis, rash, DIC, CNS involvement
  • 95. Adenovirus infection in the immunocompromised
  • 96. DIAGNOSIS  Variety of clinical specimens depending on clinical syndrome-NP, conjunctival, stool, urine, tissue, etc.  Transport in viral transport media  Isolation from pharyngeal site correlates better with current clinical infection
  • 97. Methods for diagnosis  Culture in HeLa, HEK cell lines  Shell vial cell culture  DFA  PCR, nucleic acid probes  EM and Immune EM
  • 98. Diagnosis- Enteric adenoviruses  Isolation requires special media- Graham 293  ELISA for rapid detection is available
  • 99. Prevention  Good handwashing  Contact precautions  Chlorination of water  Disinfection or sterilization of ophthalmologic equipment  Use of single dose vials  Oral vaccine- restricted
  • 100. HIV and AIDS The cellular and immunological picture - The course of the disease
  • 101. HIV and AIDS The cellular and immunological picture - The course of the disease
  • 102. HIV and AIDS The cellular and immunological picture The course of the disease 1. Acute Infection • High virus titer • Mild symptoms • Fall in CD4+ cells but recovers • Rise in CD8+ cells but recovers • A high virus titer (up to 10 million Macrophages bring HIV into the body if se viruses per ml blood)
  • 103. HIV and AIDS 2. A strong immune response Virus almost disappears from circulation • Good cytoxic T cell response • Soluble antibodies appear later against both surface and internal proteins • Most virus at this stage comes from recently activated (dividing) and infected CD4+ cells
  • 104. HIV and AIDS 3. A latent state Latency of virus and of symptoms • Virus persists in extra-vascular tissues • Lymph node dendritic cells • Resting CD4+ memory cells (last a very long time - a very stable population of cells) carry provirus
  • 105. HIV and AIDS • 10 billion HIV particles per day • Virus half life 5.7 hours • 100-10 million virions per ml blood (set point) • Small minority of T4 cells are infected • Virus found in lymph nodes
  • 106. HIV and AIDS 4. The beginning of disease Massive loss of CD4+ cells • CD4+ cells are the targets of the virus • Cells that proliferate to respond to the virus are killed by it • Dendritic cells present antigen and virus to CD4 cells • Epitope variation allows more and more HIV to escape from immune response just as
  • 107. HIV and AIDS 5. Advanced disease - AIDS CD8+ cells destroy more CD4+ cells • CD4 cell loss means virus and infected cells no longer controlled • As CD4+ cells fall below 200 per cu mm virus titer rises rapidly and remaining immune response
  • 108. HIV and AIDS Good correlation betw number of HIV particle measured by PCR an progression to disease
  • 109. HIV and AIDS Viral load predicts survival time
  • 110. HIV and AIDS CD4 cell count is not good predictor of progression to diseas
  • 111. HIV and AIDS Cofactors Not all cases of Kaposi’s are associated with HIV Not all HIV infected persons suffer from Kaposi’s 20% of homosexual HIV+ males get Kaposi’s Few IV drug users or hemophiliacs get Kaposi’s Kaposi’s sarcoma associated herpes virus Human herpes virus-8
  • 112. HIV and AIDS Three Views of AIDS Gallo: Infection by HIV is sufficient to cause AIDS Montagnier: HIV may be harmless in the absence of other co- factors Duesberg / Mullis: HIV is too silent to be the etiologic agent of AIDS. It is a much maligned by-stander So far it seems that >50% of HIV-infected persons have progressed to AIDS There is NO strong evidence there is any other infectious agent involved than HIV
  • 113. HIV - The Virus Retrovirus Membrane: host derived Three genes GAG – POL – ENV
  • 114. HIV - The Virus Retrovirus Two glycoproteins: gp160 gp120 and gp41 gp41 is fusogen that spans the membrane sugars vaccine problem ENV gene
  • 115. HIV - The Virus Retrovirus Group-Specific Antigens p17: inner surface - myristoylated p24: nucleocapsid p9: nucleocapsid associated with RNA GAG gene Polyprotein
  • 116. HIV - The Virus Enzymes Retrovirus • Polymerase (reverse transcriptase – RNA dependent DNA polymerase) • Integrase • POL gene • Protease (cuts Polyprotein polyproteins)
  • 117. The Genome of HIV Three structural genes LTRs Extra open reading frames are clue to latency
  • 118. HIV - The Virus
  • 119. HIV - The Virus Life History A retrovirus • Latency • Specific destruction of CD4+ cells
  • 120. HIV - Life History • Fusion at ambient pH • No need for entry into lysosomes •Profound significance Syncytia for AIDS progression: Spread from cell to cell Profound significance
  • 121. HIV - Life History Entry into the cell T4 (CD4+) cells are major target Human HeLa Human Cell transfected HeLa Cell with CD4 antigen NOT INFECTED INFECTED But NOT the whole answer since this does not happen if CD4 is transfected in
  • 122. HIV - Life History Why do CD4-transfected human cell but CD4-transfected mouse cells do Human cells must possess a co-factor for infection that mou Co-Receptors CD8+ Cells MIP-1 alpha MIP-1 beta RANTES Chemokines
  • 123. HIV - Life History HIV chemoki Mutant CD4 ne CCR5 CCR5 CCR5 CD4 CD4 macrophage Chemokine receptors are necessary co-recep
  • 124. HIV and AIDS Some people do not get AIDS Long term survivors Exposed uninfected persons The chemokine receptor story
  • 125. HIV and AIDS Co-receptors and HIV infection • CCR5 is a chemokine receptor • Cells with homozygous mutant CCR5 molecules are not infected by HIV 1 in 100 Caucasians No Africans • Persons with heterozygous mutant CCR5 molecules progress to AIDS more slowly
  • 126. HIV and AIDS Co-receptors • 25% of long term survivors are CCR5 or CCR2 mutants (deletions) • The same CCR5 mutation (called “delta 32”) is thought to be the mutation that rendered some people immune to the plague in the middle ages • Many other chemokine receptors
  • 127. HIV and AIDS Long term non-progressers  People who have been infected with HIV for more than seven years that have stable CD4+ cell counts above 600 per cu mm with no symptoms and no chemotherapy  Many have produced a very good immune response to the virus
  • 128. HIV and AIDS • Nairobi prostitutes Client infection rate more than 25% • Rare HLA antigens • Associations between resistance to infection and their class I and class II MHC (HLA) haplotypes
  • 129. HIV - Life History HIV is a retrovirus It carries with it: • Reverse transcriptase HIV genes • Integrase GAG POL • Protease ENV • tRNA primer HIV has no oncogene but could still be oncogenic vaccine problem
  • 130. HIV - Life History Latency – Cellular – The problem of memory T4 cells Only activated T4 cells can replicate virus Most infected T4 cells are rapidly lyzed but are replaced Some T4 cells revert to resting state as memory cells wh Memory T4 cells cannot replicate the virus unless they b Clinical Latency HIV infection is not manifested as disease for years
  • 131. Dynamics of CD4 T cells in an HIV infection Cell death Chronically- apoptosis etc infected memory T Return to cells with Infection resting Uninfected state provirus activat ed Long T cell Reactivation lived! Uninfected Cell death Long unactivated memory immune lived! Adapted from Saag and Kilby T cell pool destruction Nat Med 5: 609, 1999
  • 132. Long tern latent HIV Immune response T4 resting T4 activated It may be impossible to cure the patient o Even if combination therapy stops HIV re HIV
  • 133. Inexorable decline of CD4+ T4 cells Why do all of the T4 cells At early disappear? stages of infection only 1 in 10,000 cells is infected Of great importance to therapeutic strategy
  • 134. Virus destroys the cell as a result of budding But few cells are infected: Early stage of infection 1:10,000 Late 1:40 Why do all T4 cells 1. PUNCTURED disappear? MEMBRANE
  • 135. Why do all T4 cells disappear? - 2 But syncytia not common Infected CD4 Cells cell Most T4 cells Fuse Gp120 are not HIV+ positive Could “sweep up” Uninfected Killing of CD4 cells CD4 cell uninfected 2. Syncytium Gp120 cells Formation negative
  • 136. Why do all T4 cells disappear? Cytotox ic T cell Killing of CD4 cells 3. Cytotoxic T cell- BUT: Most mediated lysis cells are
  • 137. Killing of CD4+ cells 4. Binding of free Gp120 to CD4 antigen makes uninfected T4 cell look like an infected cell Complement- mediated lysis
  • 138. Why do all T4 cells disappear? Induction of apoptosis CD8 gp120 Macrophag HIVcell e (no CD4 antigen) chemokin e CXCR 4 G protein signal ? ? Binding to Binding to CXCR4 CXCR4 results results in in expression expression of of TNF-alpha TNF-alpha on
  • 139. Why do all T4 cells disappear? Induction of apoptosis CD8 cell CXCR 4 Macrophag Deat e h CD8 T cell
  • 140. Macrophages may be infected by two routes HIV gp120 CD4 HIV gp120 binds to macrophage CD4 antigen Virus is opsonized by anti gp120 antibodies which Fc receptor bind to macrophage Fc receptors - an Anti-gp120 vaccine problem enhancing antibody HIV
  • 141. Overview: Hepatitis  Virology  Transmission  Epidemiology  Pathogenesis  Symptoms  Diagnosis  Management  Prevention
  • 142. Viral Hepatitis - Overview Types of Hepatitis A B C D E Source of Feces Blood Blood Blood Feces Blood-derived Blood-derived Blood-derived Virus body fluids body fluids body fluids Route of Fecal-Oral Percutaneous Percutaneous Percutaneous Fecal- Trans- Permucosal Permucosal Permucosal Oral mission Chronic No Yes Yes Yes No Infection Primary Pre/Post- Pre/Post- Blood Donor Pre/Post- Ensure safe Exposure Exposure Screening Exposure drinking Prevent- Immunization water Immunization Immunization ion Risk Behavior Handwashing Risk Behavior Modification Risk Behavior Modification Modification
  • 143. Hepatitis A, B, and C at a Glance Virus Sex IDU Trans- Fecal- Occu- Course of Infection Does Vaccine fusion Oral pational Protective Available Immunity Develop? A High Low* Low High None Acute -> Resolved Yes Yes B High High Low None High Acute -> Chronic Yes Yes 90% of infants 30% in children aged 1-5 10% of older children and adults. C Low High Low None Low Acute -> Chronic No No in 75%-85% of adults.
  • 144. Age at Infection – Viral Hepatitis Perinatal Childhood Adolescent Adult HAV - ++++ ++ +++ HBV ++ ++ +++ +++++ HCV + - + +++++
  • 145. REPORTED CASES OF SELECTED NOTIFIABLE DISEASES PREVENTABLE BY VACCINATION, UNITED STATES, 2001 Hepatitis A 10,609 Hepatitis B 7,843 Pertussis 7,580 Meningococcal disease 2,333 H. influenzae, invasive 1,597 Mumps 266 Measles 116 Source: NNDSS, CDC
  • 148. Hepatitis A Virus: Structure and Classification  RNA Picornavirus • Separate genus because of differences with other enteroviruses • Naked icosahedral capsid • SS RNA (740 nucleotides) • Single serotype worldwide • Humans only reservoir
  • 149. HEPATITIS A VIRUS TRANSMISSION • Fecal-oral transmission • Close personal contact (e.g., household contact, sex contact, child day-care centers) • Contaminated food, water (e.g., infected food handlers, contaminated raw oysters) • Blood exposure (rare <<<1%) (e.g., injection drug use, rarely by transfusion)
  • 150. HEPATITIS A, UNITED STATES  Most disease occurs in the context of community- wide outbreaks  Infection transmitted from person to person in households and extended family settings - facilitated by asymptomatic infection among children  Some groups at increased risk – specific factor varies – do not account for majority of cases – Children are the most frequently infected group  No risk factor identified for 40%-50% of cases
  • 151. DISEASE BURDEN FROM HEPATITIS A UNITED STATES, 2001 Number of acute clinical 10,609 cases reported Estimated number of acute 45,000 clinical cases Estimated number of 93,000 new infections Percent ever infected 31.3%
  • 153. NUMBER OF YEARS REPORTED INCIDENCE OF HEPATITIS A EXCEEDED 10 CASES PER 100,000, BY COUNTY, 1987-1997 0-1 2-3 4-5 6-7 8-11
  • 154. Hepatitis A: Pathogenesis  Incubation 4 weeks (range 2-6 weeks)  Oral cavityGI tractliver via blood  Replicates in hepatocytes (little damage to cells) released via bile to intestines 7-10 days prior to clinical symptoms  Liver damage and clinical syndrome result of immune response and not direct effect of virus
  • 155. Hepatitis A: Clinical Features – An acute illness with:  discrete onset of symptoms (e.g. fatigue, abdominal pain, loss of appetite, intermittent nausea, vomiting)  jaundiceor elevated serum aminotransferase levels, dark urine, light stool  Adults usually more symptomatic  Patients are infective while they are shedding the virus in the stool- usually before the onset of symptoms  Mostcases resolve spontaneously in 2-4 weeks  Complete recovery 99%
  • 156. HEPATITIS A - CLINICAL FEATURES •Jaundice by <6 yrs <10% age group: 6-14 yrs 40%-50% >14 yrs 70%-80% •Rare complications: Fulminant hepatitis Cholestatic hepatitis Relapsing hepatitis •Incubation period: Average 30 days Range 15-50 days
  • 157. EVENTS IN HEPATITIS A VIRUS INFECTION Clinical illness Infection ALT IgM IgG Response Viremia HAV in stool 0 1 2 3 4 5 6 7 8 9 10 11 12 13 Week
  • 158. Hepatitis A Diagnosis  Detection of IgM antibody  IgG positive 1-3 weeks later; suggests prior infection or vaccination.
  • 159. Hepatitis A Treatment  Supportive- no specific role of antiviral therapy  Lifelong immunity likely after infection or vaccination
  • 160. PREVENTING HEPATITIS A • Hygiene (e.g., hand washing) • Sanitation (e.g., clean water sources) • Hepatitis A vaccine (pre-exposure) • Immune globulin (pre- and post- exposure)
  • 161. HEPATITIS A VACCINES • Inactivated vaccine • Highly immunogenic •97%-100% of children, adolescents, and adults have protective levels of antibody within 1 month of receiving first dose; essentially 100% have protective levels after second dose • Highly efficacious •In published studies, 94%-100% of children protected against clinical hepatitis A after equivalent of one dose
  • 162. HEPATITIS A VACCINES 1st dose at time 0 2nd dose 6-12 months afterwards
  • 163. POST-VACCINATION TESTING Not recommended:  High response rate among vaccinees  Commercially available assay not sensitive enough to detect lower (protective) levels of vaccine-induced antibody
  • 164. DURATION OF PROTECTION AFTER HEPATITIS A VACCINATION  Protection begins 4 weeks after vaccine  Persistence of antibody • At least 5-8 years among adults and children  Efficacy – No cases in vaccinated children at 5-6 years of follow-up  Mathematical models of antibody decline suggest protective antibody levels persist for at least 20 years  Other mechanisms, such as cellular memory, may contribute
  • 165. Hepatitis A Vaccine Recommendations  Vaccine is recommended for the following persons 2 years of age and older: – Travelers to areas with increased rates of hepatitis A – Men who have sex with men – Injecting and non-injecting drug users – Persons with clotting-factor disorders (e.g. hemophilia) – Persons with chronic liver disease – Children living in areas with increased rates of hepatitis A during the baseline period from 1987- 1997- mainly West Coast.
  • 166. Hep A : Passive Immunization  Hepatitis A immune globulin can be given up to 2 weeks after an exposure  Immunity temporary (4-5 months)  Also given in travelers leaving for endemic area on short notice (ie not enough time for the vaccine to be effective)
  • 167. Hepatitis A Surveillance & Response  Urgently reportable condition in S.C. – Acute HAV infection must be reported by phone to DHEC within 24 hours.  Investigation of a case of hepatitis A must be initiated by CO DADE and district epi staff within 24 hours of notification.  All cases must be reported to CDC.
  • 169.
  • 170. Hepatitis B: Structure  Member of the hepadnavirus group  Virion also referred to as Dane particle  42nm enveloped virus  Core antigens located in the center (nucleocapsid) – Core antigen (HbcAg) – e antigen (HBeAg)- an indicator of transmissibility (minor component of the core- antigenically distinct from HBcAg)  22nm spheres and filaments other forms- no DNA in these forms so they are not infectious (composed of surface antigen)- these forms outnumber the actual virions
  • 171. Structure and Replication  Circular partially double stranded DNA of virus  Initial replication to complete circular DNA with subsequent transcription to make several mRNAs some of which are translated into viral proteins   One of the mRNAs is replicated with a reverse transcriptase making the DNA that will eventually be the core of the progeny virion  Some DNA integrates into host genome causing carrier state  Virus stable and resist many stresses making them more infectious
  • 172. Hepatitis B virus particles
  • 173. Epidemiology - United States1  100,000 new infections per year  8,000 - 32,000 chronic infections/year  5,000 - 6,000 deaths/year  1.25 million Americans with chronic HBV infection – 15 to 25% of chronically infected patients will die from chronic liver disease 1. Center for Disease Control
  • 174. Geographic Distribution of Chronic HBV Infection HBsAg Prevalence 8% - High 2-7% - Intermediate <2% - Low
  • 175. High Prevalence of CHBV in Asian American Communities is Often Overlooked1  US prevalence for chronic HBV is < 2%  However, chronic HBV prevalence of 10- 15% in Asian American communities has been reported  In Asian American men living in California, HCC ranks as a leading cause death – #2 in Vietnamese and Cambodian Americans – #4 in Chinese and Korean Americans  50% of children born to mothers with chronic HBV in the US are Asian American 1. www.liver.stanford.edu
  • 176. Hepatitis B Virus Modes of Transmission • Sexual • Parenteral • Perinatal
  • 177. Concentration of Hepatitis B Virus in Various Body Fluids Low/Not High Moderate Detectable blood semen urine serum vaginal fluid feces wound exudates saliva sweat tears breastmilk
  • 178. Risk Factors for Acute Hepatitis B United States, 1992-1993 Heterosexual* (41%) Injecting Drug Use Homosexual Activity (15%) (9%) Household Contact (2%) Health Care Employment (1%) Unknown (31%) Other (1%) * Includes sexual contact with acute cases, carriers, and multiple partners. Source: CDC Sentinel Counties Study of Viral Hepatitis
  • 179. HBV Pathogenesis  Virus enters hepatocytes via blood  Immune response (cytotoxic T cell) to viral antigens expressed on hepatocyte cell surface responsible for clinical syndrome  5 % become chronic carriers (HBsAg> 6 months)  Higher rate of hepatocellular ca in chronic carriers, especially those who are “e” antigen positive  Hepatitis B surface antibody likely confers lifelong immunity  Hepatitis B e Ab indicates low
  • 180. Hepatitis B - Clinical Features • Incubation period: Average 60-90 days Range 45-180 days • Clinical illness (jaundice): <5 yrs, <10% 5 yrs, 30%-50% 1/3 adults-no symptoms • Acute case-fatality rate: 0.5%-1% • Chronic infection: <5 yrs, 30%-90% 5 yrs, 2%-10% • More likely in asymptomatic infections • Premature mortality from chronic liver disease: 15%-25%
  • 181. Hepatitis B Clinical Features  Incubation Period: 6 weeks to 6 months (av. 120 days)  Preicteric or Prodromal phase from initial symptoms to onset of jaundice usually lasts from 3 to 10 days: Non-specific, insidious onset of malaise, anorexia, n/v, RUQ pain, fever, headache, myalgias, skin rashes, arthralgias, arthritis, and dark urine beginning 1-2 days before onset of jaundice.
  • 182. Hepatitis B Clinical Features  Icteric phase usually lasts from 1-3 weeks: jaundice, light or gray stools, hepatic tenderness, hepatomegaly.  Convalescence phase may persist for weeks or months: Malaise, fatigue. Jaundice, anorexia, and other symptoms disappear.
  • 183. Hepatitis B Symptoms  About 50%-60% of adults with HBV infection have no signs or symptoms.  Those who do have symptoms might experience:  Jaundice  Fatigue  Abdominal pain  Loss of appetite  Nausea, vomiting  Joint pain
  • 184. Outcome of Hepatitis B Virus Infection 100 by Age at Infection 100 Symptomatic Infection (%) 80 80 Chronic Infection 60 60 Chronic Infection 40 40 (%) 20 20 Symptomatic Infection 0 0 Birth 1-6 months 7-12 months 1-4 years Older Children and Adults Age at Infection
  • 185. Possible Outcomes of HBV Infection Acute hepatitis B 95% of infection 3-5% of infant- Chronic HBV adult- acquiredinfection acquired infectionsChronic infections 12-25% in hepatitis 6-15% in 5 Cirrhosi years 5 20-23% in years Hepatocell s 5 years Liver ular failure Death carcinoma Liver Death
  • 186. Acute Hepatitis B Virus Infection with Recovery Typical Serologic Course Symptoms HBeAg anti-HBe Total anti-HBc Titer HBsAg IgM anti-HBc anti-HBs 0 4 8 12 16 20 24 28 32 36 52 100 Weeks after Exposure
  • 187. Progression to Chronic Hepatitis B Virus Infection Typical Serologic Course Acute Chronic (6 months) (Years) HBeAg anti-HBe HBsAg Total anti- HBc Titer IgM anti- HBc 0 4 8 1 1 2 2 2 3 3 5 Years Weeks 6 0 4 8 2 6 2 after Exposure 2
  • 188.
  • 189. INTERPRETATION OF THE HEPATITIS B PANEL Tests Results Interpretation HBsAg Negative Susceptible Anti-HBc Negative Anti-HBs Negative HBsAg Negative Immune Anti-HBc Negative or Positive Anti-HBs Positive HBsAg Positive Anti-HBc Positive Acute Infection IgM Anti-HBc Positive Anti-HBs Negative HBsAg Positive Chronic Infection Anti-HBc Positive IgM Anti-HBc Negative Anti-HBs Negative HBsAg Negative Four possible interpretations Anti-HBc Positive Anti-HBs Negative
  • 190. Interpretation HBsAg negative HBcAb positive HBsAb negative 1. May be recovering from acute infection. 2. May be distantly immune and test is not sensitive enough to detect very low level of HBsAb in serum. 3. May be susceptible with a false positive HBcAb. 4. May be undetectable level of HBsAg present in the serum and the person is actually a carrier.
  • 191. Current Treatment Options for HBV  Pegylated Interferon alfa (Intron A)  Lamivudine (Epivir HBV)  Adefovir dipivoxil (Hepsera)
  • 192. Elimination of Hepatitis B Virus Transmission United States Strategy • Prevent perinatal HBV transmission • Routine vaccination of all infants • Vaccination of children in high-risk groups • Vaccination of adolescents – all unvaccinated children at 11-12 years of age – “high-risk” adolescents at all ages
  • 193. Hepatitis B Vaccine  Infants: several options that depend on status of the mother – If mother HepBsAg negative: birth, 1-2m,6- 18m – If mother HepBsAg positive: vaccine and Hep B immune globulin within 12 hours of birth, 1-2m, <6m  Adults – 0, 1, 6 months  Vaccine recommended in – All those aged 0-18 – Those at high risk
  • 194. Hepatitis B High Risk Groups  Persons with multiple sex partners or diagnosis of a sexually transmitted disease  Men who have sex with men  Sex contacts of infected persons  Injection drug users  Household contacts of chronically infected persons  Infants born to infected mothers  Infants/children of immigrants from areas with high rates of HBV infection  Health care and public safety workers  Hemodialysis patients
  • 195. Estimated Incidence of Acute Hepatitis B United States, 1978-1995 80 HBsAg screening Infant Vaccine of pregnant immunization 70 licensed women recommende recommended d 60 OSHA Rule 50 enacted Population Cases per Adolescent 100,000 40 immunization recommende d 30 20 * Decline among Decline 10 among homosexual men & injecting 0 HCWs drug users 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 * Provisional date Year
  • 196. Hepatitis B: Passive Immunization  Infants of surface antigen positive mothers  Exposures to infected blood or infected body fluids in individuals who are unvaccinated, unknown vaccination, or known non- responders. – Ideally within 24 hours – Probably not effective >7days post exposure
  • 197. Hepatitis B Surveillance  Acute Hepatitis B is an urgently reportable condition. It must be reported by phone to DHEC within 24 hours.  Chronic Hepatitis B is a reportable condition and must be reported to DHEC within 7 days.  Perinatal Hepatitis B is a reportable condition and must be reported to
  • 198. Hepatitis B Surveillance  Acute,chronic, and perinatal hepatitis B must be reported to CDC.  CDC and S.C. conducts enhanced surveillance on acute and perinatal hepatitis B cases.
  • 199. Hepatitis D (Delta) Virus antigen HBsAg RNA
  • 200. Hepatitis D Structure  Defective virus that requires co- infection with hepatitis B for replication  Enveloped with SS RNA genome  Onlyantigen encoded in the delta antigen
  • 201. Hepatitis D virus genome
  • 202. Hepatitis D Virus Modes of Transmission • Percutaneous exposures – injecting drug use • Permucosal exposures – sex contact
  • 203. Geographic Distribution of HDV Infection Taiwan Pacific Islands HDV Prevalence High Intermediat e Low Very Low No Data
  • 204. Hepatitis D:Pathogenesis  Pathogenesis – Immune mediated – Co-infection- infection with B at the same time (more severe) – Superinfection: acquisition of Hep D in chronically Hep B
  • 206. Hepatitis D - Clinical Features • Coinfection –severe acute disease –low risk of chronic infection • Superinfection –usually develop chronic HDV infection –high risk of severe chronic liver disease
  • 207. HBV - HDV Coinfection Typical Serologic Course Symptoms ALT Elevated anti- Titer IgM anti- HBs HDV HDV RNA HBs Ag Total anti-HDV Time after Exposure
  • 208. HBV - HDV Superinfection Typical Serologic Course Jaundice Symptoms Total anti-HDV ALT Titer HDV RNA HBsAg IgM anti-HDV Time after Exposure
  • 210. Hepatitis D - Prevention • HBV-HDV Coinfection Pre or postexposure prophylaxis to prevent HBV infection • HBV-HDV Superinfection Education to reduce risk behaviors among persons with chronic HBV infection • Alpha interferon may help reduce hepatocellular damage
  • 211. Hepatitis C viruses particles and genome
  • 212. Hepatitis C Structure and Classification  Member of the flavivirus family (other members yellow fever and dengue)  Enveloped single stranded RNA virus  Humans and chimpanzees only known reservoirs  6 serotypes (genotypes) and multiple subtypes based on high variability of envelope glycoproteins
  • 213. Hepatitis C Virus Infection, United States New infections per year 1985-89 242,000 2001 25,000 Deaths from acute liver failure Rare Persons ever infected (1.8%) 3.9 million (3.1-4.8)* Persons with chronic infection 2.7 million (2.4-3.0)* HCV-related chronic liver disease 40% - 60% Deaths from chronic disease/year 8,000-10,000 *95% Confidence Interval
  • 214. Estimated Incidence of Acute HCV Infection United States, 1960-2001 140 New Infections/100,000 120 100 Decline in injection 80 drug users 60 40 Decline in transfusion recipients 20 0 1960 1965 1970 1975 1980 1985 1989 1992 1995 1998 2001 Year Source: Hepatology 2000;31:777-82; Hepatology 1997;26:62S-65S; CDC, unpublished data
  • 215. Exposures Known to Be Associated With HCV Infection in the United States  Injecting drug use  Transfusion, transplant from infected donor  Occupational exposure to blood – Mostly needle sticks  Iatrogenic (unsafe injections)  Birth to HCV-infected mother  Sex with infected partner – Multiple sex partners
  • 216. Sources of Infection for Persons With Hepatitis C Injecting drug use 60% Sexual 15% Transfusion 10% (before screening) Occupational 4% Other 1%* Unknown 10% * Nosocomial; iatrogenic; perinatal Source: Centers for Disease Control and Prevention
  • 217. Posttransfusion Hepatitis C 30 All volunteer donors HBsAg % of Recipients Infected 25 20 15 Donor Screening for HIV Risk Factors Anti-HIV 10 ALT/Anti-HBc Anti-HCV 5 Improved HCV Tests 0 1965 1970 1975 1980 1985 1990 1995 2000 Year Adapted from HJ Alter and Tobler and Busch, Clin Chem 1997
  • 218. Injecting Drug Use and HCV Transmission  Highly efficient – Contamination of drug paraphernalia, not just needles and syringes  Rapidly acquired after initiation – 30% prevalence after 3 years – >50% after 5 years  Four times more common than HIV
  • 219. Occupational Transmission of HCV  Inefficient by occupational exposures  Average incidence 1.8% following needle stick from HCV-positive source – Associated with hollow-bore needles  Case reports of transmission from blood splash to eye; one from exposure to non-intact skin  Prevalence 1-2% among health care workers – Lower than adults in the general population – 10 times lower than for HBV infection
  • 220. Perinatal Transmission of HCV  Transmission only from women HCV- RNA positive at delivery – Average rate of infection 6% – Higher (17%) if woman co-infected with HIV – Role of viral titer unclear  No association with – Delivery method – Breastfeeding  Infected infants do well – Severe hepatitis is rare
  • 221. Sexual Transmission of HCV  Occurs, but efficiency is low – Rare between long-term steady partners – Factors that facilitate transmission between partners unknown (e.g., viral titer)  Accounts for 15-20% of acute and chronic infections in the United States Partner studies – Low prevalence (1.5%) among long-term partners  infections might be due to common percutaneous exposures (e.g., drug use), BUT – Male to female transmission more efficient  more indicative of sexual transmission
  • 222. Household Transmission of HCV  Rare but not absent  Could occur through percutaneous/mucosal exposures to blood – Contaminated equipment used for home therapies  IV therapy, injections – Theoretically through sharing of contaminated personal articles (razors, toothbrushes)
  • 223. Other Potential Exposures to Blood  No or insufficient data showing increased risk – intranasal cocaine use, tattooing, body piercing, acupuncture, military service  No associations in acute case-control or population-based studies  Cross-sectional studies in highly selected groups with inconsistent results – Temporal relationship between exposure and infection usually unknown – Biologically plausible, but association or causal relationship not established
  • 224. Hep C: Pathogenesis  Blood-borne pathogen that infects hepatocytes  Much like Hep A and B, liver damage and clinical illness due more to elicited immune response as opposed to direct cytopathic effect of the virus  Likely cytotoxic T cells that mediate most of the damage  Like other chronic liver diseases (Hep B and chronic alcoholism), can cause hepatocellular ca (HCC)  Some genotypes more amenable to therapy- i.e. 3a
  • 225. Features of Hepatitis C Virus Infection Incubation period Average 6-7 weeks Range 2-26 weeks Acute illness (jaundice) Mild (<20%) Case fatality rate Low Chronic infection 60%-85% Chronic hepatitis 10%-70% (most asx) Age- Cirrhosis related <5%-20% Mortality from CLD 1%-5%
  • 226. Hepatitis C: Clinical Features  Acuteinfection asymptomatic in over 80% of patients, when present, acute illness usually mild – Acute symptoms include jaundice, nausea, abdominal pain, loss of appetite, dark urine
  • 227.
  • 228. Hepatitis C: Extrahepatic Manifestations  Seen with chronic infection  ? Due to immune complexes  Extrahepatic manifestations – Essential mixed cryoglobulinemia (vasculitis, skin rash, fatigue) – Porphyria cutanea tarda – Membranoproliferative glomerulonephritis – ?Diabetes mellitus – Other autoimmune disease – ?Lymphoma
  • 230. Chronic Hepatitis C Factors Promoting Progression or Severity  Increased alcohol intake  Age > 40 years at time of infection  HIV co-infection  Other – Male gender – Chronic HBV co-infection
  • 231. Serologic Pattern of Acute HCV Infection with Recovery anti- Symptoms +/- HCV HCV RNA Titer ALT Norm 0 1 2 3 al 5 6 1 2 3 4 4 Mont Year Time after Exposure hs s
  • 232. Serologic Pattern of Acute HCV Infection with Progression to Chronic Infection anti- Symptoms +/- HCV HCV RNA Titer ALT Norm 0 1 2 3 4 al 6 1 2 3 4 5 Mont Year Time after Exposure hs s
  • 233. Hepatitis C: Diagnosis  ELISA-a serological test which is usually. positive within 2-5 months after infection – 3rd generation assays now 99% specific and sensitive  Confirmatory testing – PCR (positive 1-2 weeks post infection) both quantitative and qualitative (I.e. ye/no) available – RIBA (recombinant immunoblot assay)- looks for 2 or more antibodies to HCV viral antigens  Genotype testing done when treatment anticipated
  • 234. HCV Testing Routinely Recommended Based on increased risk for infection  Ever injected illegal drugs  Received clotting factors made before 1987  Received blood/organs before July 1992  Ever on chronic hemodialysis  Evidence of for exposure management Based on need liver disease  Healthcare, emergency, public safety workers after needle stick/mucosal exposures to HCV-positive blood  Children born to HCV-positive women
  • 235. HCV Infection Testing Algorithm for Diagnosis of Asymptomatic Persons Screening Test for Negative STOP Anti-HCV Positive OR RIBA for Negative NAT for HCV Anti-HCV RNA Negative Indeterminate Positive Positive Additional Laboratory Medical STOP Evaluation (e.g. PCR, ALT) Evaluation Negative PCR, Positive PCR, Normal ALT Abnormal ALT Source: MMWR 1998;47 (No. RR 19)
  • 236. Medical Evaluation and Management for Chronic HCV Infection  Assess for biochemical evidence of CLD  Assess for severity of disease and possible treatment, according to current practice guidelines – 40-50% sustained response to antiviral combination therapy (peg interferon, ribavirin) – Vaccinate against hepatitis A  Counsel to reduce further harm to liver – Limit or abstain from alcohol
  • 237. Hepatitis C Therapy  Standard of care is pegylated interferon alpha and ribavirin  Many barriers to treatment as the above regimen is difficult to take and has many systemic side effects (fatigue, myalgias, depression, ane mia to name a few)  Overall response rate to treatment
  • 238. Postexposure Management for HCV  IG, antivirals not recommended for prophylaxis  Follow-up after needlesticks, sharps, or mucosal exposures to HCV-positive blood – Test source for anti-HCV – Test worker if source anti-HCV positive  Anti-HCV and ALT at baseline and 4-6 months later  For earlier diagnosis, HCV RNA at 4-6 weeks – Confirm all anti-HCV results with RIBA  Refer infected worker to specialist for medical evaluation and management
  • 240. Hepatitis E  Non-enveloped single stranded RNA virus  Resembles calicivirus or Norwalk agent  Similarillness to Hep A except high mortality in pregnant women
  • 241. Geographic Distribution of Hepatitis E Outbreaks or Confirmed Infection in >25% of Sporadic Non-ABC Hepatitis
  • 242. Hepatitis E - Epidemiologic Features • Most outbreaks associated with fecally contaminated drinking water • Minimal person-to-person transmission • U.S. cases usually have history of travel to HEV-endemic areas
  • 243. Hepatitis E - Clinical Features • Incubation period: Average 40 days Range 15-60 days • Case-fatality rate: Overall, 1%-3% Pregnant women, 15%-25% • Illness severity: Increased with age • Chronic sequelae: None identified
  • 244. Hepatitis E Virus Infection Typical Serologic Course Symptoms ALT IgG anti- HEV IgM anti- Titer HEV Virus in stool 0 1 2 3 4 5 6 7 8 9 1 1 1 1 Weeks after Exposure 0 1 2 3
  • 245. Prevention and Control Measures for Travelers to HEV-Endemic Regions • Avoid drinking water (and beverages with ice) of unknown purity, uncooked shellfish, and uncooked fruit/vegetables not peeled or prepared by traveler • IG prepared from donors in Western countries does not prevent infection • Unknown efficacy of IG prepared from donors in endemic areas • Vaccine?
  • 246.
  • 247.
  • 249. „FLU‟  True influenza – influenza virus A or influenza virus B (or influenza virus C infections - much milder)  Febrilerespiratory disease with systemic symptoms caused by a variety of other organisms often inaccurately called „flu‟
  • 250. South Carolina 1996-1997 DHEC bulletin malathia influenzae per le stel no virus CULTURE RESULTS influenza A influenza B http://www.state.sc.us/dhec/LAB/labbu017.htm
  • 251. THE IMPACT OF INFLUENZA PANDEMICS Deaths: 1918-19 Spanish flu 500,000 US 20,000,000 world 1957-58 Asian flu 70,000 US
  • 252. THE IMPACT OF INFLUENZA  In the United States, on average:  36,000 deaths per year  114,000 hospitalizations per year CDC: MMWR 53:8-11, 2004
  • 253. THE IMPACT OF INFLUENZA  recently some increase in morbidity and mortality - possible factors? – more elderly people – CF patients live longer – more high risk neonates – more immunosuppressed patients
  • 254. ORTHOMYXOVIRUSES pleomorphic influenza types A,B,C febrile, respiratory illness with systemic symptoms http://www.uct.ac.za/depts/mmi/stannard/fluvirus.ht
  • 255. ORTHOMYXOVIRUSES HA - hemagglutinin NA - neuraminidase helical nucleocapsid (RNA plu NP protein) lipid bilayer membrane polymerase complex M1 protein type A, B, C : NP, M1 protein sub-types: HA or NA protein
  • 256. TRANSMISSION  AEROSOL – 100,000 TO 1,000,000 VIRIONS PER DROPLET  18-72 HR INCUBATION  SHEDDING
  • 257. NORMAL TRACHEAL MUCOSA 3 DAYS POST-INFECTION 7 DAYS POST-INFECTION Lycke and Norrby Textbook of Medical Virology 1983
  • 258. DECREASED CLEARANCE  RISK BACTERIAL INFECTION  VIREMIA RARE Lycke and Norrby Textbook of Medical Virology 1983
  • 259. RECOVERY  INTERFERON - SIDE EFFECTS INCLUDE: – FEVER, MYALGIA, FATIGUE, MALAISE  CELL-MEDIATED IMMUNE RESPONSE  TISSUE REPAIR – CAN TAKE SOME TIME
  • 260. An immunological diversion INTERFERON
  • 261. INTERFERON timecourse of virus production will vary fro
  • 263. INTERFERON antiviral state antiviral state antiviral state antiviral state
  • 264. INTERFERON antiviral state antiviral state antiviral state antiviral state
  • 265. INTERFERON antiviral state antiviral state antiviral state antiviral state
  • 266. INTERFERON THE VIRUSES ARE COMIN PAUL REVERE http://www.mfa.org/collections/one_hour/6.htm http://www.paulreverehouse.org/midnight.html
  • 267. TYPES OF INTERFERON TYPE I Interferon-alpha (leukocyte interferon, about 20 related proteins) - leukocytes, etc Interferon-beta (fibroblast interferon) - fibroblasts, epithelial cells, etc
  • 268. INDUCTION OF INTERFERON interferon-alpha and interferon- beta - viral infection (especially RNA viruses), double stranded RNA, certain bacterial components - strong anti-viral properties interferon-gamma - antigens, mitogenic stimulation lymphocytes
  • 269. INTERFERON  induces variety of proteins in target cells  manyconsequences, not all fully understood
  • 270. INTERFERON-ALPHA AND INTERFERON-BETA
  • 271. interferon-alpha, interferon-beta interferon receptor induction of induction of induction of 2’5’oligo A synthase ribonuclease L protein kinase R (PKR) ds RNA 2’5’oligo A ds RNA activated activated activated 2’5’oligo A synthase ribonuclease L protein kinase R ATP ATP phosphorylated 2’5’oligo A initiation factor (eIF- 2) mRNA degraded inhibition of protein synthesi
  • 272. interferons  only made when needed
  • 273. OTHER EFFECTS OF INTERFERONS  ALL TYPES – INCREASE MHC I EXPRESSION  CYTOTOXIC T-CELLS – ACTIVATE NK CELLS  CAN KILL VIRALLY INFECTED CELLS
  • 274. OTHER EFFECTS OF INTERFERONS  INTERFERON-GAMMA – INCREASES MHC II EXPRESSION ON APC  HELPER T-CELLS – INCREASES ANTIVIRAL POTENTIAL OF MACROPHAGES  INTRINSIC  EXTRINSIC
  • 275. THERAPEUTIC USES OF INTERFERONS  ANTI-VIRAL – e.g. interferon-alpha is currently approved for certain cases of acute and chronic HCV and chronic HBV  MACROPHAGE ACTIVATION – interferon-gamma has been tried for e.g. lepromatous leprosy, leishmaniasis, toxoplasmosis  ANTI-TUMOR – have been used in e.g. melanoma, Kaposi‟s sarcoma, CML  MULTIPLE SCLEROSIS
  • 276. Viral response to host immune system Viruses may : block interferon binding inhibit function of interferon-induced proteins inhibit NK function interfere with MHC I or MHC II expression block complement activation inhibit apoptosis etc!
  • 277. SIDE EFFECTS OF INTERFERONS  FEVER  MALAISE  FATIGUE  MUSCLE PAINS
  • 279. PROTECTION AGAINST RE-INFECTION  IgG and IgA – IgG less efficient but lasts longer  antibodies to both HA and NA important – antibody to HA more important (can neutralize)
  • 280. SYMPTOMS  FEVER  HEADACHE  MYALGIA  COUGH  RHINITIS  OCULAR SYMPTOMS
  • 281. CLINICAL FINDINGS  SEVERITY – VERY YOUNG – ELDERLY – IMMUNO- COMPROMISED – HEART OR LUNG DISEASE
  • 282. PULMONARY COMPLICATIONS  CROUP (YOUNG CHILDREN)  PRIMARY INFLUENZA VIRUS PNEUMONIA  SECONDARY BACTERIAL INFECTION – Streptococcus pneumoniae – Staphlyococcus aureus – Hemophilus influenzae
  • 283. NON-PULMONARY COMPLICATIONS  myositis (rare, > in children, > with type B)  cardiac complications  recent studies report encephalopathy – 2002/2003 season studies of patients younger than 21 yrs in Michigan - 8 cases (2 deaths)  liver and CNS – Reye‟s syndrome  peripheral nervous system – Guillian-Barré syndrome
  • 284. Reye‟s syndrome  liver - fatty deposits  brain - edema  vomiting, lethargy, coma  risk factors – youth – certain viral infections (influenza, chicken pox) – aspirin
  • 285. Guillian-Barré syndrome  1976/77 swine flu vaccine – 35,000,000 doses  354 cases of GBS  28 GBS-associated deaths  recent vaccines much lower risk
  • 286. MORTALITY  MAJORCAUSES OF INFLUENZA VIRUS- ASSOCIATED DEATH – BACTERIAL PNEUMONIA – CARDIAC FAILURE  90%OF DEATHS IN THOSE OVER 65 YEARS OF AGE
  • 287. DIAGNOSIS  ISOLATION – NOSE, THROAT SWAB – TISSUE CULTURE OR EGGS  SEROLOGY  PCR  RAPID TESTS  provisional - clinical picture + outbreak
  • 288. ANTIGENIC DRIFT  HA and NA accumulate mutations – RNA virus  immune response no longer protects fully  sporadic outbreaks, limited epidemics
  • 289. ANTIGENIC SHIFT  “new” HA or NA proteins  pre-existing antibodies do not protect  may get pandemics
  • 290. INFLUENZA A PANDEMICS Ryan et al., in Sherris Medical Microbiology
  • 291. where do “new” HA and NA come from? 13 types HA  9 types NA – all circulate in birds  pigs – avian and human
  • 292. Where do “new” HA and NA come from?
  • 293. Where do “new” HA and NA come from - can „new‟ bird flu directly infect humans? Bird flu H5N1?
  • 294.
  • 295. why do we not have influenza B pandemics?  so far no shifts have been recorded  no animal reservoir known
  • 297. actual percentage of deaths (CDC MMWR July 1, 2005 / 54(25);631-634)
  • 298. % typed cases 100 90 80 70 60 H1N1 50 H3N2 40 B 30 20 10 0 00/01 01/02 02/03 03/04 04/05 influenza
  • 299. VACCINE  „BEST GUESS‟ OF MAIN ANTIGENIC TYPES – CURRENTLY  type A - H1N1  type A - H3N2  type B  each year choose which variant of each subtype is the best to use for optimal protection
  • 300. VACCINE  inactivated  egg grown  some formulations licensed for children  reassortant live vaccine approved 2003 – for healthy persons (those not at risk for complications from influenza infection) ages 5-49 years
  • 301. CDC
  • 302. OTHER TREATMENT  REST, LIQUIDS, ANTI-FEBRILE AGENTS (NO ASPIRIN FOR AGES 6MTHS-18YRS)  BEAWARE OF COMPLICATIONS AND TREAT APPROPRIATELY
  • 303. VIRAL AGENTS CAUSING GASTROENTERITIS
  • 304. VIRAL AGENTS CAUSING GASTROENTERITIS 1. Rotavirus 2. Enteric adenoviruses 3. Calicivirus 4. Astrovirus
  • 306. ROTAVIRUS  First isolated in 1973 from children with diarrhea  EM identification from duodenal biopsies  Human and animal strains
  • 309. STRUCTURAL FEATURES OF ROTAVIRUS  60-80nm in size  Non-enveloped virus  EM appearance of a wheel with radiating spokes  Icosahedral symmetry  Double capsid  Double stranded (ds) RNA in 11 segments
  • 310. STRUCTURE  Double capsid (outer and inner capsid)  Core with genome  Capsid is cleaved by trypsin to form  ISVP- infective sub-viral particle
  • 314. VIRAL STRUCTURAL PROTEINS (VP)  Outer structural proteins - VP7 and VP4 VP7 - Glycoprotein VP4 - protease-cleaved, P protein, viral hemagglutinin; forms spikes from the surface  Inner core structural proteins VP 1, 2, 3, 6  VP6 is an important antigenic
  • 316. CLASSIFICATION  Groups- 7 Groups (A through G) based on VP6 differences Group A is the most common and has 2 subgroups
  • 317. CLASSIFICATION (contd.)  Serotypes based on viral capsid proteins  14 G serotypes based on G protein (VP 7) differences  20 P serotypes based on P protein (VP4)  Common PG combinations are:- P8G1, P8G2, P4G2, P8G4
  • 318. CLASSIFICATION (contd.)  Electropherotypes are based on the mobility of RNA segments by PAGE  Useful in epidemiologic studies
  • 319. ROTAVIRUS- PROPERTIES  Virus is stable in the environment  Relatively resistant to handwashing agents  Susceptible to disinfection with 95% ethanol, „Lysol‟, formalin
  • 320. PATHOGENESIS  Targeted host cells - mature enterocytes lining the tips of intestinal villi  Intermediate/infective sub-viral particle (ISVP) produced through proteolysis  Enter host cell by endocytosis  Virus replicates in the host cell cytoplasm
  • 321. REPLICATION  mRNA transcription with viral RNA polymerase  Capsid proteins formed  mRNA segments formed, assembled into immature capsid  mRNA replicated to form double stranded RNA genome
  • 322. HISTOPATHOLOGY  Mature enterocytes lining the tips of intestinal villi are affected  Villous atrophy and blunting  Death of the mature enterocytes
  • 323. HISTOPATHOLOGY  Infiltration of lamina propria with mononuclear cells  Repopulation of the villous tips with immature secretory cells [crypt hyperplasia]
  • 325. EPIDEMIOLOGY A major cause of diarrhea- associated hospitalizations and deaths  Seroprevalence studies show that antibody is present in most by age 3y.
  • 326. ROTAVIRAL DISEASE BURDEN- World
  • 327. WORLDWIDE DISTRIBUTION OF ROTAVIRUS (Source- Centers for Disease Control and Prevention)
  • 328. EPIDEMIOLOGY - USA  2.7- 3.5 million affected each year  Physician visits ~ 500,000/year  50,000-70,000 hospitalizations/year  20-40 deaths/year  Cases with dehydration ~ 1-2.5%  Economic impact
  • 329. EPIDEMIOLOGY  Age- 4mo - 2 years Protection of younger infants through through transplacental antibody transfer  Asymptomatic infections are common, especially in adults  Nosocomial infections  Outbreaks  Severe Disease young, immunocompromised
  • 330. Epidemiology (contd.)  Seasonality Winter months (Nov. through May in US) Gradual spread W to E Year-round in the tropics  Incubation period - thought to be <4 days
  • 331. EPIDEMIOLOGY (Source- Centers for Disease Control and Prevention)
  • 332. SEASONAL SPREAD - U.S. (Source- CDC)
  • 333. TRANSMISSION  Mainly person to person via fecal-oral route  Fomites  Foodand water-borne spread is possible  Spreadvia respiratory route is speculated
  • 334. EPIDEMIOLOGY - spread  Contagious from before onset of diarrhea to a few days after end of diarrhea  Large amounts of viral particles are shed in diarrheal stools  Infective dose is only 10-100 pfu
  • 335. EPIDEMIOLOGY Differences in Groups  Group A infections are most common  Group B has been associated with outbreaks in adults in China  Group C is responsible for sporadic cases of diarrhea in infants around the world
  • 336. CLINICAL CASE  A 22 month old female is admitted to the pediatric ward for cough and fever up to 103 F.  Chest X ray shows left lower lobe pneumonia.  She is being treated with intravenous Ceftriaxone and her fever is gradually improving.  On hospital day #5, she develops diarrhea with 4 watery stools and a fever of 102 F.  Stool studies showed no traces of blood and no fecal leukocytes.  Further studies are pending.
  • 337. CLINICAL FEATURES  Incubation period - thought to be <4 days  Fever- can be high grade (>102 F in 30%)  Vomiting, nausea precede diarrhea  Diarrhea • usually watery (no blood or leukocytes) • lasts 3-9 days • longer in malnourished and immune deficient individuals. • NEC and hemorrhagic GE seen in neonates
  • 338. MECHANISM OF DIARRHEA  Watery diarrhea due to net secretion of intestinal fluid  Activation of the enteric nervous system  Role of NSP4 peptide regions as an enterotoxin
  • 339. CLINICAL FEATURES (contd.)  Dehydration is the main contributor to mortality.  Secondary malabsorption of lactose and fat, and chronic diarrhea are possible
  • 340. DIAGNOSIS  Antigen detection in stool by ELISA, LA (for Group A rotavirus)  EM- non-Group A viruses also  Culture- Group A rotaviruses can be cultured in monkey kidney cells  Serology for epidemiologic studies
  • 341. TREATMENT AND PREVENTION  Treatment Supportive- oral, IV rehydration  Prevention Handwashing and disinfection of surfaces
  • 342. VACCINE  Live tetravalent rhesus-human reassortant vaccine (Rotashield)  Licensed for use in August 1998  Removed from the market in October 1999 due to risk of intussusception  Cases were seen 3-20 days after vaccination  Approx. 15 cases/1.5 million doses
  • 343. NEWER VACCINES Rotarix Rota Teq  Monovalent G1P8 oral  Pentavalent Human- vaccine bovine reassortant vaccine  Efficacy for prevention  Efficacy for prevention of severe disease = of severe disease = 85% 100%
  • 345. GASTROENTERITIS DUE TO ADENOVIRUS  Types 40, 41  Belong to serogroup F
  • 346. Diarrhea due to Enteric Adenovirus  Age <4 years  Year round  Spread via fecal-oral route
  • 347. CLINICAL FEATURES- Adenovirus gastroenteritis  Incubation period 3 -10 days  Diarrhea lasts for 10 -14 days  Can also cause intussusception, mesenteric adenitis, appendicitis
  • 348. DIAGNOSIS Enteric adenoviruses  Isolation requires special media- Graham 293  ELISA for rapid detection is available
  • 350. HUMAN CALICIVIRUSES (HuCV) • Family Caliciviridae • Non-enveloped RNA viruses with ss RNA • 27-35 nm in size • Contain a single capsid protein
  • 351. HUMAN CALICIVIRUSES  Genomic analysis divides it into 4 groups Human caliciviruses belong to 2 genera
  • 352. CLASSIFICATION OF HuCV NLV (Norovirus) SLV (Sapovirus) Norwalk virus Sapporo virus Hawaii virus Manchester virus Snow Mountain virus Houston/86 Montgomery county London/92 virus Taunton (England)
  • 353. MORPHOLOGY- typical • 32 cup-like depressions • EM appearance of “Star of David” • 31-35 nm size • E.g.- Sapporo-like viruses
  • 355. Morphology of HuCV- atypical • Smaller size- approx. 27 nm • Rough, feathery surface but no internal pattern • Small Round Structured viruses • E.g.- Norwalk-like viruses
  • 357. CLINICAL FEATURES  Usual incubation Period is <24 hours (ranges from 12hrs. to 4 days)  Short duration of illness <3 days  Nausea, vomiting, fever, headache  Abdominal cramping  Watery diarrhea
  • 358. EPIDEMIOLOGY - Noroviruses  Worldwide distribution  >23 million cases/year in the U.S.  Major cause of foodborne outbreaks of GE (>50%)  Most people have had infections by age 4 years (by seroprevalence studies)
  • 359. SPREAD  Person-to-person Fecal-oral spread (stool/vomitus)  Fecal contamination of food or water  Spread through fomites (stool/vomitus)
  • 360. SPREAD- Viability of Caliciviruses  Survive in water chlorinated at routine levels (up to 10 ppm)  Survive freezing, heating up to 60 C  Evidently survive in steamed shellfish
  • 361. EPIDEMIOLOGY • Asymptomatic infections- seroconversion but asymptomatic shedding of virus • Low infective dose (~10 pfu) • Viral excretion during convalesence (~ 2 wk.)
  • 362. EPIDEMIOLOGY : Outbreaks  Cruise ships, schools, nursing homes,  Can involve infants and school-age children  Source usually is contaminated food and water (E.g. seafood-oyster and shellfish, salads, cake icing, raw fruit etc.)  Rapid secondary spread
  • 363. DIAGNOSIS  Specimen- stool, vomitus, environmental swabs (during outbreak investigations)  RT-PCR in state public health labs.  Serology for epidemiologic purposes  Immune EM is less used
  • 365. ASTROVIRUS  Described in relation to an outbreak of gastroenteritis in 1975  Detected by EM  Immunologically distinct from Human Caliciviruses  Belong to family Astroviridae  8 human serotypes are known