Adenoviruses can replicate and produce disease in
respiratory, gastrointestinal and urinary tract and
in the eye.
Many adenovirus infection are subclinical and
virus persist in hosts for months.
One third of 51 serotypes are responsible for most
cases of human adenovirus disease.
Whereas a few types serve as models for cancer
induction in animal models.
Are double stranded DNA viruses having icosahedral
symmetry and measures 70-90 nm in diameter.
Capsid composed of 252 capsomeres; in which 12 are
penton bases and has fibers projecting from each of 12
vertices or penton bases and rest of capsid is composed
of 240 hexon capsomeres.
The hexon, penton and fiers constitute major antigens
of adenovirus important in viral classification and
The DNA genome (25-45 Kb) is linear and double
The penton bases carry toxin like activity and
causes rapid appearance of cytopathic effects
and detachment of the cells from the surface
on which they are growing.
Fibers contain type specific antigens important
in serotyping and has hemagglutinating
Family Adenoviridae is classified into two genera:
Mastadenovirus, the adenovirus of mammals.
Aviadenovirus; adenovirus of birds
At least 51 distinct antigenic types have been isolated
from humans and many other types from various
Human adenovirus have been divided into six groups
(A-F) on the basis of their genetic, physical, chemical
and biological properties.
They are divided into serotypes on the basis of type
specific antigens on penton bases and fibers.
Serotypes are identified by neutralization tests.
Infect and replicate in epithelial cells of respiratory
tract, gastrointestinal tract, urinary tract and the eye.
Do not spread beyond regional lymph nodes.
Group C persists as latent infections for years in
adenoids and tonsils and are shed in feces for many
months after initial infection.
Most adenovirus replicate in intestinal epithelium after
ingestion but usually produce sub clinical infection
than overt symptoms.
About 1/3 of human serotypes are commonly
associated with human illnesses.
Single serotype may cause different clinical diseases
and conversely more than one serotype can cause same
Adenoviruses 1-7 are more common types worldwide
and account for most instances of adenovirus associated
Responsible for 5% of respiratory diseases in young
children but account for much less in adults.
Most infections are mild and self limited.
Occasionally case disease in other organs particularly
eye and gastrointestinal tract.
o Respiratory Diseases:
Typical symptoms: cough, nasal congestion, fever and sore
Symptoms most commonly manifested in infants and
children and usually involves group C viruses.
Adenoviruses particularly 3, 7 and 21 are thought to be
responsible for about 10-20% pneumonias in childhood.
Mortality rate of pneumonia 8-10% in very young.
Also are cause of acute respiratory disease syndrome among
Characterised by fever, sorethroat, nasal congestion, cough
and malaise; sometimes leading to pneumonia.
Occurs in epidemic form among young
military recruits under conditions of fatigue,
stress, and crowding soon after induction.
Disease is caused by serotype 4 and 7 and
occasionally by type 3.
Outbreak of severe respiratory disease in 2007
caused by adenovirus 14 affects all age
• Eye Infections:
Mild occular involvement may be part of respiratory pharyngeal
Pharyngoconjunctival fever occurs as outbreak such as in children’s
summer camps (swimming pool conjunctivitis) and caused by type 3
Duration 1-2 weeks and complete recovery with no lasting sequelae
is common outcome.
Epidemic keratoconjunctivitis more serious disease; occurs mainly
in adults and is highly contagious.
Source of infection: sinks and hand towel.
Disease is characterises by acute conjunctivitis followed by keratitis
that usually resolves in two weeks but may leave subepithelial
opacities in the cornea for up to two years.
o Gastrointestinal disease:
Can often been isolated from feces but their relation to
intestinal disease has not been conclusively established.
However two serotypes (types 40 and 41) have been
etiologically associated with infantile gastroenteritis.
May account for 5-15% cases of viral gastroenteritis in
Adenoviruses 40 and 41 are abundantly present in
Enteric adenovirus are very difficult to cultivate.
Stool ELISA is often used for detection of these types.
o Other Diseases:
Cause variety of casual and severe diseases in
Most common problem in transplant patients is
respiratory diseases that may progress to pneumonia
and may be fatal (usually types 1-7).
Adenovirus hepatitis in children having liver transplant.
AIDS patients mainly suffer from gastroenteritis due to
Types 11 and 21 may cause acute hemorrhagic cystitis
in children esp. boys.
o Specimen: throat washings, stool, urine and eye for
Samples should be collected from affected sites as early
Duration of excretion of the virus varies among various
1-3 days from throat of adults with common cold,
3-5 days for throat, stool and eyes, for
2 weeks eye for keratoconjunctivitis,
3-6 weeks, throat and stool of children with respiratory
2-12 months in stool, throat, urine of immunocompromised
Viral isolation in cell culture requires human cells.
Human epithelial cell lines such as Hep-2, HeLa and
BK are sensitive but difficult to maintain.
Isolates grown in these cells are identified by noting
cytopathic effects or by immunofluorescence staining
using anti hexon antibody , heamagglutination
inhibition test and neutralization test.
Shell vial techniques can also be employed for isolation
of the virus.
Can also be detected by electron microscopy, ELISA or
by latex agglutination tests.
Paired sera should be used to detect rise in
Antibodies in patients sera can be detected by
ELISA, complement fixatation test,
heamagglutination inhibition and neutralization
o Molecular techniques:
PCR, restriction endonuclease digestion, DNA
o Treatment: no specific treatment
• Belongs to reoviridae family.
• First identified as cause of diarrhea in 1973.
• Double stranded RNA virus having icosahedral symmetry.
• 60-80 nm in diameter and have double capsid shell
• Non enveloped virus.
• Rota in Latin means wheel.
• Under electron microscope resembles as little wheel with short spokes
radiating from wide hub to a clearly defined outer rim.
• Complete or double shelled virus measures 70nm and incomplete single
shelled virus is smaller about 60 nm.
• Double stranded RNA as genome with 10-12 discrete segments.
• Contains nine structural proteins; core contains several enzymes.
• Major cause of infantile diarrhoea.
Classification and Antigenic Properties:
Classified into 5 species (A-E) plus two tentative species (F and G)
based on antigenic epitopes on the internal structural protein VP6.
These can be detected by ELISA, immune electron microscopy.
Group A major human pathogen.
Outer capsid proteins VP4 and VP7 carry epitopes important in
neutralizing activity with VP7 predominant antigen.
Group A have been divided into subgroups I and II by ELISA, CF
or immune adherence agglutination and into serotypes (1,2,3 etc.) by
The virus enters the body through the mouth.
Infects cells in the villi of small intestine (gastric
and colonic mucosa are spared).
Multiply in the cytoplasm of the enterocytes and
damage their transport mechanisms.
Rotavirus encoded protein NSP4, is viral
enterotoxin and induces secretion by triggering
signal transduction pathway.
Damaged cells may slough off into the lumen of
the intestine and release large quantities of virus.
Viral excretion lasts from 2 to 12 days.
Diarrhoea caused by rotavirus is due to
impaired sodium and glucose absorption as
damaged cells on villi are replaced by
nonabsorbing immature crypt cells.
It may take 3-8 weeks for normal function to
Cause major portion of diarrhoeal illness in infants and
children world wide but not in adults.
Incubation period:1-3 days
Typical symptoms include watery diarrhoea, fever,
abdominal pain and vomiting leading to dehydration.
Stools usually greenish yellow or pale with no blood or
Group B rotavirus have been implicated in large
outbreaks of severe gastroenteritis in adults in China.
The most widely available method for confirmation of
rotavirus infection is detection of rotavirus antigen in
stool by enzyme-linked immunoassay (EIA) or by
immune electron microscopy.
Polymerase chain reaction most sensitive method.
ELISA can be employed for detection of rise in
treatment: no specific treatment; supportive rehydration
Prophylaxis:RV5 (RotaTeq); a live oral vaccine and
RV1 (Rotarix), a live oral vaccine
• The Norwalk virus was first identified in 1968 after a severe
outbreak of “winter vomiting” in a school in Norwalk Ohio.
• The descendents of Norwalk virus are now called noroviruses
because these viruses change shape slightly about every 4 years so
there is no virus that is exactly the same as the one discovered in
1968, but still related.
Belongs to Calciviridae family.
Single stranded RNA viruses having icosahedral symmetry.
Size: 27-40 nm in diameter, non enveloped virus.
genome: single stranded, linear, positive sense, non segmented
• Major cause of nonbacterial epidemic gastroenteritis.
• Epidemic nonbacterial gastroenteritis is characterised by:
I. Absence of bacterial pathogens
II. Gastroenteritis with rapid onset and recovery and relatively
mild systemic signs;
III. An epidemiological pattern of a highly communicable disease
that spreads rapidly with no particular predilection in terms of
age and geography.
Various descriptive terms used: epidemic viral
gastroenteritis, winter vomiting disease, viral diarrhoea
depending on predominant clinical feature.
• Mode of transmission: through food, indirect contact or direct
• Incubation period: 24-48 hours
• The onset is rapid and clinical course is brief, lasting 12-48 hours.
• symptoms: diarrhoea, nausea, vomiting, low-grade fever, abdominal
cramps, headache and malaise.
• Dehydration is the most common complication in young and adults.
• Most people will recover from this sickness in about 24-72 hours
without any long term problems.
• Viral shedding persists for as long as 1 month.
• No sequelae have been reported.
Specimen: feces and vomitus
Electron Microscopy and Immunoelectron Microscopy
can be used for detection of virus in stool samples.
ELISA is used to detect rise in antibody titre in patient
Real-Time reverse transcriptase-polymerase chain
reaction (RT-qPCR) is the most common way of testing
samples for the virus in stool and vomitus and also in
environmental samples (contaminated food and water).
treatment: no specific treatment; only supportive
• 28-38nm in diameter, exhibit distinctive starlike
• Contain single stranded positive sense RNA.
• Astroviridae consists two genera.
• All human viruses are classified in Mamastrovirus
• At least 8 serotypes of human viruses are
Cause diarrhoeal illness and may shed in
extraordinarily in large quantities in feces.
The virus is transmitted by fecal-oral route
through contaminated food and water, person-
person contact, or contaminated surfaces.
They are recognised as pathogens for infants and
children, elderly institutionalized patients and
Shed for prolonged periods in feces by