# Poliovirus and Enteroviruses

> Poliovirus and enteroviruses for MBBS Microbiology: picornavirus properties, AFP stool surveillance, bOPV switch, coxsackie and echovirus syndromes.

- Canonical URL: https://prepelephant.com/topics/mbbs/microbiology/poliovirus-and-enteroviruses
- Exam / course: MBBS · Subject: Microbiology
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-02
- Last updated: 2026-10-02
- How to cite: "Poliovirus and Enteroviruses", PrepElephant, https://prepelephant.com/topics/mbbs/microbiology/poliovirus-and-enteroviruses

## Direct answer

Three serotypes of poliovirus — Brunhilde, Lansing and Leon — and two vaccines carry the story of India's proudest public-health certification: wild poliovirus-free status on 27 March 2014, after the last case in Howrah on 13 January 2011. The virus is a small, non-enveloped, positive-sense single-stranded RNA picornavirus: acid-stable, it survives gastric passage, replicates in oropharynx and gut, and in a minority reaches anterior horn cells to produce asymmetric flaccid paralysis without sensory loss. The same family supplies coxsackieviruses (herpangina, hand-foot-mouth disease, myocarditis), echoviruses (viral meningitis) and enterovirus 71 (hand-foot-mouth disease with brainstem encephalitis). Surveillance rests on acute flaccid paralysis reporting with stool isolation in RD and L20B cell lines.

## What you must remember

- **Structure:** Picornaviridae, enterovirus genus; icosahedral, non-enveloped capsid of 60 protomers enclosing positive-sense ssRNA — ether-resistant, acid-stable at pH 3, surviving chlorination standards of the past and spreading faeco-orally.
- **Serotypes:** three antigenically distinct types with no cross-protection — type 1 (Brunhilde) most paralytogenic, type 2 (Lansing), type 3 (Leon); type 1 caused India's last wild infections.
- **Pathogenesis:** replication in Peyer's patches and tonsils → minor viremia → crosses the blood-brain barrier to anterior horn motor neurons → lower motor neuron flaccid paralysis, asymmetric, with preserved sensation; over 99% of infections are subclinical.
- **Vaccine contrast:** Sabin oral poliovaccine — live attenuated, secretory IgA and contact spread, risk of vaccine-associated paralytic poliomyelitis; Salk inactivated poliovaccine — injectable, humoral only, no VAPP, no shedding.
- **Programme milestones:** global wild type 2 eradicated 2015 and type 3 in 2019; the trivalent-to-bivalent OPV switch on 27 April 2016 removed the type 2 component to end cVDPV2 risk; India's UIP uses bOPV with fractional-dose IPV.
- **AFP surveillance:** every case of acute flaccid paralysis in a child under 15 must be notified and investigated — two stool samples collected at least 24 hours apart within 14 days of onset, transported frozen, inoculated into RD and L20B cell lines with intratypic differentiation by PCR.
- **Coxsackieviruses:** group A — herpangina, hand-foot-mouth disease (A16 and EV71), flaccid paralysis; group B — pleurodynia (Bornholm disease), myocarditis, pericarditis, aseptic meningitis, and epidemiological links to type 1 diabetes.
- **Echoviruses and EV-D68:** echoviruses lead viral meningitis in children; EV-D68 causes severe respiratory illness with a flaccid-weakness overlap that mimics polio.

## From stool bottle to certification

Walk one notified case through the system. A district hospital reports a four-year-old with sudden left-leg weakness and reduced tone, notified as acute flaccid paralysis within 24 hours. Two stool bottles arrive — collected on consecutive days, kept cold — and are inoculated into RD and L20B cell lines at the reference laboratory. Cytopathic effect resembling enterovirus undergoes intratypic differentiation by PCR: wild, vaccine-derived or Sabin-like. Clinical follow-up at 60 days grades residual paralysis, and the national expert committee classifies the case polio or non-polio AFP — run at scale with sewage sampling, this machinery converts thousands of Indian notifications into the confidence behind "polio-free".

The vaccine logic deserves the same walking-through. Poor seroconversion in tropical guts demanded repeated OPV doses — hence pulse polio rounds delivering supplementary doses to every child under five on a single day. But OPV's type 2 component itself caused circulating vaccine-derived poliovirus outbreaks once wild type 2 vanished, so the world switched to bivalent OPV and elevated IPV's role to restore type 2 immunity without live virus. That single trade — mucosal spread and affordability versus genetic reversion — is the entire endgame logic examiners probe.

## Viva favourites

The OPV-versus-IPV table is guaranteed airtime: contact immunity, secretory IgA, cost, heat lability and VAPP on one side; safety and humoral-only protection on the other. The dates are quotable currency — 13 January 2011, 27 March 2014, 27 April 2016 — and examiners reward the reasoning behind the switch more than the dates themselves. Hand-foot-mouth questions test the coxsackie A16 versus enterovirus 71 severity axis: same vesicles, but EV71 adds brainstem encephalitis. Keep the family logic ready — acid stability, faeco-oral spread, summer peaks and a multi-syndrome presentation point to enterovirus in any vignette.

## Frequently asked questions

### Name the three poliovirus serotypes.

Types 1, 2 and 3 — Brunhilde, Lansing and Leon respectively — antigenically distinct with no cross-immunity; type 1 is the most paralytogenic.

### What stool protocol follows a case of acute flaccid paralysis?

Two stool specimens at least 24 hours apart, within 14 days of onset, transported cold for isolation in RD and L20B cell lines with intratypic differentiation.

### What is vaccine-associated paralytic poliomyelitis?

Paralysis from reversion of the Sabin vaccine strain to neurovirulence, roughly once per million first doses — the price of a live vaccine that IPV avoids.

### Why was trivalent OPV switched to bivalent OPV in April 2016?

Wild poliovirus type 2 had been eradicated (2015), so its vaccine component caused more paralytic disease (cVDPV2) than it prevented; the switch removed it while IPV restored type 2 immunity.

### Which enteroviruses cause hand-foot-mouth disease, and which is feared?

Coxsackievirus A16 causes typical mild disease; enterovirus 71 causes outbreaks with brainstem encephalitis, pulmonary oedema and deaths — the one to respect.