Virology: Enteroviruses
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Questions and Answers

Rotavirus attaches to the cell surface at the site of which receptor?

  • D-adrenergic receptor
  • A-adrenergic receptor
  • B-adrenergic receptor (correct)
  • C-adrenergic receptor
  • What is synthesized from each of the segments within the cytoplasm?

  • DNA
  • tRNA
  • rRNA
  • mRNA (correct)
  • What is the result of rotavirus replication in the mucosal cells of the small intestine?

  • No effect on fluids and electrolytes
  • Excess secretion of fluids and electrolytes (correct)
  • Decreased secretion of fluids and electrolytes
  • Increased absorption of fluids and electrolytes
  • What is the duration of watery diarrhea in rotavirus gastroenteritis?

    <p>3-9 days</p> Signup and view all the answers

    What is the incubation period of rotavirus?

    <p>1-4 days</p> Signup and view all the answers

    What is the age range of children who are most commonly affected by rotavirus?

    <p>Infants and young children</p> Signup and view all the answers

    What is the method used for the detection of rotavirus in stool?

    <p>Electron microscopy</p> Signup and view all the answers

    What is the type of diarrhea seen in rotavirus gastroenteritis?

    <p>Watery diarrhea</p> Signup and view all the answers

    What is the consequence of rotavirus replication in the small intestine?

    <p>Consequent loss of salt, glucose, and water</p> Signup and view all the answers

    What is the characteristic of fever in rotavirus gastroenteritis?

    <p>High-grade fever (&gt;102°F) in 30%</p> Signup and view all the answers

    Study Notes

    Enteroviruses

    • Enteroviruses are transient inhabitants of the human alimentary tract and can be isolated from the throat or lower intestine.
    • There are four types of enteroviruses:
      • Enterovirus 68: isolated from respiratory tract of children with bronchiolitis or pneumonia.
      • Enterovirus 70: causes acute hemorrhagic conjunctivitis, highly contagious, and transmitted person-to-person via fingers, fomites.
      • Enterovirus 71: isolated from patients with meningitis, encephalitis, and paralysis resembling poliomyelitis, and causes CNS disease and diarrhea.
      • Enterovirus 72: also known as Hepatitis A virus.

    Echoviruses (Enteric Cytopathogenic Human Orphan viruses)

    • There are 33 serotypes of ECHO viruses.
    • They are not pathogenic for mice, unlike polioviruses, and do not cause diseases in monkeys.
    • Incubation period: 2-9 days.
    • They can cause opportunistic infections and diseases such as:
      • Aseptic meningitis
      • Rash, common in young children
      • Conjunctivitis
      • Muscle weakness and spasms
      • Infantile diarrhea
      • Congenital and neonatal disease
      • Cardiac disease

    Rhinoviruses

    • Rhinoviruses are isolated chiefly from the nose, conjunctiva, and throat, rather than the lower respiratory tract.
    • They are acid-labile, killed by gastric acid when swallowed, which explains why they do not infect the gastrointestinal tract.
    • The virion consists of a capsid shell of 60 submits, each of four protein (VP1-VP4) arranged in icosahedral symmetry around the ssRNA positive sense genome.
    • More than 100 serotypes exist.
    • Incubation period: 2-4 days.
    • Mode of transmission:
      • Direct: person-to-person via aerosols of respiratory droplets.
      • Indirect: via contaminated hands or surfaces.
    • Replication cycle:
      • Replicates better at 33°C than 37°C.
      • Replication is similar to that of poliovirus.
      • Cell surface receptor: ICAM-1 (Intercellular adhesion molecule-1).
    • Clinical findings:
      • Associated with acute, febrile upper respiratory disease (common cold).
      • No specific antiviral therapy available.
      • Vaccines appear impractical due to the large number of serotypes.
      • Prevention: use paper tissues impregnated with citric acid and sodium lauryl sulfate.

    Reoviruses

    • Reoviruses are respiratory and enteric viruses that were initially isolated from the respiratory and enteric tracts.
    • The family of reoviridae is divided into twelve genera.
    • Rotavirus is the most important cause of infantile gastroenteritis worldwide.

    Rotavirus

    • Rotavirus was first identified by electron microscopy in 1973 from duodenal biopsies of children with diarrhea.
    • Electron microscopic appearance: a wheel with radiating spokes (Latin, Rota = wheel).
    • Important properties:
      • Medium in size (60-80nm in diameter).
      • Double-stranded linear, segmented RNA genome (10-11 segments).
      • Surrounded by a double-layer icosahedral capsid (outer capsid, inner capsid) without an envelope.
      • Replication occurs in cytoplasm, virions not completely uncoated.
      • Acid-labile but relatively stable in the environment.
      • Susceptible to disinfection with 95% ethanol, 'Lysol', and formalin.
    • Proteins:
      • Six viral proteins (VPs): VP1, VP2, VP3, VP4, VP6, and VP7.
      • Six nonstructural proteins (NSPs): NSP1, NSP2, NSP3, NSP4, NSP5, and NSP6.
    • Types of rotavirus:
      • Five species: A, B, C, D, and E.
      • Humans are primarily infected by species A, B, and C, most commonly by species A.
      • Within rotavirus A, there are different strains, called serotypes.
    • Mode of transmission: fecal-oral route.
    • Replication cycle:
      • Attach to the cell surface at the site of B-adrenergic receptor.
      • RNA-dependent RNA polymerase synthesizes mRNA from each of the segments within the cytoplasm.
      • mRNA are translated into structural and non-structural proteins.
      • One of these proteins, RNA polymerase, synthesizes minus strands that will become part of the genome of the progeny virus.
      • Capsid proteins form an incomplete capsid around the minus strands, and then the plus strands of the progeny segments are synthesized.
      • The virus is released from the cytoplasm by lysis of the cell.
    • Clinical features:
      • Most common cause of severe diarrhea among infants and young children.
      • Nearly every child in the world has been infected with rotavirus at least once by the age of five.
      • Immunity develops with each infection, so subsequent infections are less severe; adults are rarely affected.
      • Incubation period: 1-4 days.
      • Symptoms: fever, nausea, vomiting, watery diarrhea, and low-grade fever.
      • Rotavirus replicates in the mucosal cells of the small intestine, resulting in excess secretion of fluids and electrolytes into the bowel lumen, leading to watery diarrhea.
    • Diagnosis:
      • Electron microscopy for detection of rotavirus in stool.
      • Culture: group A rotaviruses can now be cultured in monkey kidney cells.
      • Latex agglutination for rapid diagnosis. Several kits are commercially available.

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    Learn about the characteristics and types of enteroviruses, including their habitats and transmission methods.

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