This document provides information on picornaviruses including enteroviruses. It discusses the classification, properties, laboratory diagnosis and clinical features of important enteroviruses such as poliovirus, coxsackievirus, echovirus and newer enteroviruses 68-72. Poliovirus is described in more detail including its morphology, antigenic properties, pathogenesis of paralytic poliomyelitis, and prevention through polio vaccines.

1. Dr V S Vatkar
Asso Prof
Microbiology Department
D Y Patil Medical College, Kolhapur

2. INTRODUCTIONUnder picornavirus group
Small RNA viruses
Non-enveloped, 20 to 30 nm
Classification
Enterovius: infects GIT
Rhinivirus: infects nasopharynx
Hepatovirus
parechovirus

4. HISTORY
Paralytic Ds of children
Landsteiner & Popper: demonstrated experimental
transmission of ds in monkeys
Ender, Weller & Robbins (1948) Nobel Prize:
demonstrated growth in non neural cell culture like:
human embryo cells , shows cytopathic changes

5. ENTEROVIRUSES
Viruses of the enteric tract
Most stable viruses
1) Poliovirus type 1 – 3
2) Coxsackievirus A (1 – 24)
3) Coxsackievirus B (1 – 6)
4) Echovirus (1 – 34)
5) Enteroviruses types 68 - 72

6. POLIOVIRUS
Affinity for nervous tissues
Morphology :
Size 27-30 nm
SS RNA
60 capsomeres (subunits)
Viral Proteins(VP1-VP4)
Icosahedral symmetry
• VP1: major antigenic site for combination with type specific neutralizing Ab

7. RESISTANCE
Resistant to ether ,chloroform , bile &
proteolytic enzymes of the intestinal tract,
detergents
In feces : can survive up to month at 4 0 C
Stable at pH 3
years at -20°C
55°C 30 mins
MgCL2 protects the virus from heat inactivation.
Does not survive lyophilisation
Formaldehyde & oxidising disinfectants: destroy
virus

8. ANTIGENIC PROPERTIES
Poliovirus strains classified into 3 types by
neutralization test – 1,2, and 3
Type 1: the commonest & causes most epidemics
Type 2: causes endemic infections
Type 3: causes epidemics, type specific
2 Antigens are recognized by CFT , ELIZA or
PPTn test -

9. Antigen C : heated or H Ag, associated with
empty or non - infectious virus, anti C Ab : not
protective, not neutralizes viral infectivity
Antigen D: native or N Ag, associated with whole
virion, type specific
Antigen D is converted to Antigen C by heating
the virus at 56°C, anti D Ab protective
Potency of injectable polio vaccine : measured in
terms of D Ag units.

10. PATHOGENESIS
Transmission: Virus enters by oral route through
ingestion food & water contaminated with human
feces.
Colonizes the nasopharynx & multiply initially
Found in throat & feces in initial phases
Then passes down to Peyer’s patches & epithelial cells
of alimentary canal & lymphatic system
Inhalation of droplets can also be a mode of entry

11. Goes to regional gr of LN
Enters into blood stream (Primary Viremia)
Further multiplication in reticuloendothelial system
Virus again re-enters into blood stream (secondary
Viremia)
Virus goes to spinal cord & brain (pass along axons of
peripheral nerves to CNS)

12. In CNS: virus multiplies selectively in neurons &
destroys them.
Degeneration of Nissl body (earliest change)
Degeneration : irreversible, necrotic cell lyses or
phagocytosis by leucocytes or macrophages
Anterior horn cells of spinal cord : mostly
involved, causes flaccid paralysis, post horn cells may
also involved

13. Direct neural transmission to the CNS may occur
in special cases as in poliomyelitis, following
tonsillectomy
 Some cases encephalitis may occur , involves
brainstem extending up to motor & premotor
areas of cerebral cortex

14. CLINICAL FEATURES
Inapparent infection: exposed to polio virus, 90-
95% susceptible individuals develop inapparent
infection, causes seroconversion only.
Only 5-10% cases show clinical illness
I P : 10 days (range 4 days – 4 weeks)
Abortive poliomyelitis: (minor illness)- earliest
manifestations like fever, headache, sore throat,
malaise , last for 1-5 days

15. CLINICAL FEATURES
Paralytic poliomyelitis: (Major illness)-
If the infection progresses ,the minor illness is followed by
major illness in 3-4 days
 Fever again (biphasic fever) with headache ,stiff neck and
other signs of meningitis- stage of viral invasion of the CNS
Flaccid paralysis : depending on distribution of paralysis,
classified as SPINAL, BULBAR or SPINOBULBAR
Mortality is 5-10 % mainly due to respiratory failure
Recovery of paralised ms : next 4-8 wks, complete after 6
mnths, leaving behind varying degrees of residual paralysis
Non paralytic poliomyelitis: ds dose not progress beyond
aseptic meningitis.

19. LAB. DIAGNOSIS
Specimen: throat swab, feces (rectal swab), blood &
CSF
Viral Isolation:
Isolated from blood: primary viremia, little imp, can
be isolated from throat swab at this stage
Feces: possible 80% cases in 1st
wk, 50% till 3rd
wk, 25%
till 6th
wk.
CSF:

20. Primary monkey kidney cell or tissue culture
(human or simian cell culture)
Growth: detected by CYTOPATHIC effects in 2-3
days
Identification by neutralization test with pooled or
specific antisera
SEROLOGY: antibody rise: paired sera or CFT
MOLECULAR diagnosis: Reverse Transcriptase
PCR: demo of viral RNA in CSF
Sequencing: 3 types of strains : wild virus, Oral Polio
Vaccine Virus (OPV), Vaccine derived poliovirus
(VDPV)

21. PROPHYLAXIS
2 types of vaccines :
Active
immunization
a) Killed polio
vaccine (Salk)
b) Live attenuated
OPV (Sabin)
www.polioeradication.org
Polio
Paralysis for life Primarily affects children
Preventable with OPV

22. SALKS KILLED POLIO VACCINE/INACTIVATED
POLIO VACCINE
Dev.by Salk in 1953
Formalin inactivated prep. of 3 t/o polio viruses, grown on
monkey kidney tissue culture, inactivated with formaline
(1:4000) at 37 0 C for 12-15 days
Deep subcut.or IM injection
Produces long lasting immunity
Induces serum antibodies IgM & IgG
Does not induce IgA in the intestine and hence not able to
prevent alimentary tract infections

23. Vaccination schedule
Three doses, given 4-6 weeks apart
Booster dose six months later
1st
dose: after 6 mnths: maternal Ab does not interfere
2nd
dose: 4 -6 wks after 1st
dose, induses better
seroconversion
3rd
dose: 6-12 mnths later,
immunity lasts for 3-5 yrs, after booster dose

24. LIVE ATTENUATED OPV/SABIN VACCINE
Dev.by Koprowsky, Cox & Sabin in 1962
Contains live attenuated strains of polio viruses 1,2 and 3
Shelf life 4 M at 4 - 8°C and 2 yrs.at -20°C
Improper storage conditions and cold chain failure –
problem in dev.countries
Administered orally
Stimulates both IgA and humoral antibodies IgG and IgM

25. OPV used in INDIA: contains
Type 1 virus : 10 lakhs
Type 2 virus : 2 lakhs
Type 3 virus : 3 lakhs
TC ID50 per dose ( 0.5 ml)
Stabilized by MgCl2
pH: 7.0

26. Safety
OPV : tends to acquire neurovirulence on serial
enteric passages, may seen following vaccination.
Incidence ; very low.
Vaccine associated paralytic polio or Vaccine
Derived Polio Virus (VDPV): rare strain of polio virus,
very rarely OPV strain converts into VDPV strain,
polio myelitis following vaccination
Contraindication:
immunodeficient/immunocompromised person

27. Vaccination schedule
Live attenuated OPV
3 doses orally
Zero dose (0 dose): at birth
First dose along with DPT at
4-6 weeks (1 & 1/2mnth)
2nd and 3rd – at an interval
of 4-6 weeks
Booster dose at the age of
16 – 24 months

28. Issues related to vaccine failure
Interference by other entero V, may be
Coxsackie B
Frequent diarrhoea : prevents colonization
of virus in gut
Breast feeding before & after vaccination
(maternal Ab present in breast milk)
Inhibitors of polio V : present in saliva
Proper maintenance of cold chain

29. PULSE POLIO IMMUNIZATION
To eradicate polio myelitis from India
Mass immunization of OPV on a single day to all
children aged 0-5 years in the community
Irrespective , whether they are vaccinated or not,
through Universal Immunization Program (UPI)
Two doses at the interval of 4-6 wks during low
polio transmission period (Nov to Feb)
Herd immunity: produced in the community

30. EPIDEMIOLOGY
Exclusively a Human
disease
Feces- imp. source of
spread of virus in the
community
Warm weather –
conducive to virus
spread
Type 1 – causes
epidemics
Type 2 – paralytic
poliomyelitis
WHO- 13th
May 1988-
Global eradication by

31. COXSACKIEVIRUS
1949 in Coxsackie village of NY
Resemble polio viruses in properties & epi.
Infects suckling mice but not the adult mice
Classified in 2 groups, based on the patho.changes they
produce
Group A and Group B
By neutralization test –
Group A – divided into 24 types
Group B - divided into 6 types

32. GROUP A COXSACKIE VIRUSES
1. Aseptic meningitis
2. Herpangina
(Vesicular pharyngitis) –
caused by types
2,4,5,6,8 and 10
Abrupt onset of
fever,pharyngitis ,pain in
abdomen,
headache

33. 3. Hand-foot and
Mouth disease –
caused by types 5
and 16
Presents as a
vesicular lesion
involving hands,
mouth and feet

34. GROUP B COXSACKIE VIRUSES
1. Epidemic myalgia – Bornholm disease
Fever, stitch like pain in chest & abdo.
2. Myocarditis and Pericarditis – newborn
3. Aseptic meningitis with paralysis
4. Juvenile diabetes –
5. Neonatal infections –
Hepatitis,meningoencephalitis

35. Lab. diagnosis
Virus isolation from feces or the lesions
a. Inoculation into suckling mice
b. Tissue culture – kidney cells of monkeys

36. ECHOVIRUSES
Enteric Cytopathogenic Human Orphan (ECHO) viruses
34 types – 1 to 34 except 10 and 28 (Rhinoviruses)
Alimentary tract
Faeco-oral route
Some echoviruses agglutinate human RBC’s
Resistant to 20% ether

37. CLINICAL FEATURES
Most infections are asymptomatic
Rash with fever
Resp.diseases
Paralysis
Infantile diarrhoea
Pericarditis and
Aseptic meningitis

39. Lab. diagnosis
Specimens are :
1. Throat secretions
2. Stool
3. CSF
Isolation of the virus – inoculation into
kidney cells of monkey

40. ENTEROVIRUSES 68 - 72
68 : Isolated from pharyngeal secretions of children with
pneumonia and bronchitis
69 : Not asso. with any human disease
70 : Acute hemorrhagic conjunctivitis
71 : Isolated from cases of meningitis & encephalitis
72 : Hepatitis virus type A