Microbiology · MU Sofia

87. Family Picornaviridae – Poliovirus and Other Enteroviruses

Covers the general features of the Picornaviridae family, including its small non-enveloped capsid, positive-sense RNA genome and acid-stable, faecal-oral spread, then moves to the genus Enterovirus. Poliovirus receives the fullest treatment: serotypes, pathogenesis, clinical forms from abortive to bulbar disease, diagnosis, and the differences between OPV and IPV. A comparison table of other enteroviruses and their diseases, plus supportive care and prevention, close the note.

Inside: 10 sections · 5 labelled pictures · 2 tables · 15 flashcards · 3 min

Topic 87 of 113 in the MU Sofia syllabus for Microbiology (Dental Medicine, Year 2). The free AceMed note covers it in 10 sections, about 310 words (3 min of reading), with 15 flashcards.

In this note

  1. Family Picornaviridae – Poliovirus and Other Enteroviruses
  2. I. General Characteristics of Picornaviridae
  3. II. Structure and Genome
  4. III. Genus Enterovirus
  5. IV. Poliovirus (Virus poliomyelitidis)
  6. D. Diagnosis
  7. E. Prevention
  8. V. Other Clinically Important Enteroviruses
  9. VI. Laboratory Diagnosis
  10. VII. Treatment and Prevention

I. General Characteristics of Picornaviridae

  • Family Picornaviridae = pico (small) + RNA.
  • Small, non-enveloped, icosahedral viruses.
  • Positive-sense single-stranded RNA genome.
  • Replicate in the cytoplasm of host cells.
  • Stable in acidic environments → resistant to gastric acid → fecal–oral transmission.
  • Divided into several genera; clinically important ones include:
  • Enterovirus (Poliovirus, Coxsackievirus, Echovirus, Enterovirus D68)
  • Rhinovirus (common cold — NOT acid-stable)
  • Hepatovirus (Hepatitis A virus)

III. Genus Enterovirus

  • Transmission: Fecal–oral (except Enterovirus D68 — respiratory).
  • Tropism: Initially infects gut-associated lymphoid tissue, then spreads hematogenously.
  • Asymptomatic infection is common, but viruses can target CNS, heart, skin, conjunctiva, etc.

IV. Poliovirus (Virus poliomyelitidis)

A. Overview

  • 3 serotypes: PV1, PV2, PV3 (PV1 most common in outbreaks).
  • Causes poliomyelitis — highly infectious neurotropic virus.
  • Human is the only reservoir.

B. Pathogenesis

  • Enters via oropharynx or intestine → replicates in Peyer’s patches.
  • Spreads via blood (viremia) → CNS.
  • Targets anterior horn cells of spinal cord → motor neuron death → flaccid paralysis.

C. Clinical Manifestations

  • Asymptomatic (90%).
  • Abortive poliomyelitis (minor illness): sore throat, fever, headache.
  • Non-paralytic poliomyelitis: aseptic meningitis.
  • Paralytic poliomyelitis:
  • Flaccid asymmetric paralysis.
  • No sensory loss.
  • Bulbar poliomyelitis → respiratory failure.

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