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Questions and Answers
Rotavirus attaches to the cell surface at the site of which receptor?
Rotavirus attaches to the cell surface at the site of which receptor?
What is synthesized from each of the segments within the cytoplasm?
What is synthesized from each of the segments within the cytoplasm?
What is the result of rotavirus replication in the mucosal cells of the small intestine?
What is the result of rotavirus replication in the mucosal cells of the small intestine?
What is the duration of watery diarrhea in rotavirus gastroenteritis?
What is the duration of watery diarrhea in rotavirus gastroenteritis?
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What is the incubation period of rotavirus?
What is the incubation period of rotavirus?
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What is the age range of children who are most commonly affected by rotavirus?
What is the age range of children who are most commonly affected by rotavirus?
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What is the method used for the detection of rotavirus in stool?
What is the method used for the detection of rotavirus in stool?
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What is the type of diarrhea seen in rotavirus gastroenteritis?
What is the type of diarrhea seen in rotavirus gastroenteritis?
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What is the consequence of rotavirus replication in the small intestine?
What is the consequence of rotavirus replication in the small intestine?
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What is the characteristic of fever in rotavirus gastroenteritis?
What is the characteristic of fever in rotavirus gastroenteritis?
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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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Description
Learn about the characteristics and types of enteroviruses, including their habitats and transmission methods.