[07.10] Agents of Viral Gastroenteritis V2.pdf

Rotavirus

Which virus is the most common etiological agent for diarrhea in both developing and developed countries?

Infants and young children

In which specific age group is rotavirus the most common cause of diarrhea?

Norovirus

Which virus is the major cause of nonbacterial epidemic gastroenteritis in the world?

Adults

In which age group is the Norwalk virus (Norovirus) the most important cause of epidemic viral gastroenteritis?

Icosahedral

What is the virion shape of the Reovirus family?

60–80 nm

What is the typical diameter of a Reovirus virion?

Double capsid shell

How is the capsid of a Reovirus virion structured?

dsRNA (Double-stranded RNA)

What is the genetic composition of the Reovirus genome?

Segmented (10–12 segments)

Is the Reovirus genome segmented or non-segmented?

Linear

What is the physical shape of the Reovirus genome?

16–27 kbp

What is the total genome size of the Reovirus family?

9

How many structural proteins are found in a Reovirus?

None (Pseudo-envelope during morphogenesis)

Do Reoviruses typically have an envelope?

Cytoplasm

Where does replication occur for the Reovirus family?

They are not completely uncoated

What is unique about the uncoating of Reovirus virions during replication?

Genetic reassortment

Which process occurs readily in Reoviruses because of their segmented genome?

15

How many genera is the family Reoviridae divided into?

Orthoreovirus, Rotavirus, Coltivirus, Orbivirus

Which four genera of the family Reoviridae are able to infect humans?

Spinareovirinae and Sedoreovirinae

What are the two subfamilies of the family Reoviridae?

Spinareovirinae

Which subfamily of Reoviridae contains viruses with large spikes at the 12 vertices of the particle?

Sedoreovirinae

Which subfamily of Reoviridae appears smoother and lacks large surface projections?

Orthoreovirus

Provide an example of a genus in the Spinareovirinae subfamily.

Rotavirus

Provide an example of a genus in the Sedoreovirinae subfamily.

Demonstrable by neutralization and hemagglutination-inhibition tests

How are the three distinct types of Reoviruses recovered from various species identified?

Human O or bovine erythrocytes

Reoviruses contain hemagglutinin specifically for which types of cells?

Outer capsid proteins

Which part of the Reovirus virion primarily determines its pathogenic properties?

Adulthood

By what stage of life do most people have serum antibodies against Reoviruses?

Healthy children and minor febrile illnesses

In what clinical context have Reoviruses been recovered from children?

Feces

Reoviruses have been more readily recovered from which site: feces or the nose/throat?

7 (A to G)

How many species or groups of rotaviruses are currently recognized?

Group H

Which group of rotavirus has been recently proposed?

A, B, and C

Which groups of rotaviruses are known to infect humans?

Group A

Which rotavirus group antigen is the most frequent human antigen?

VP6

Rotavirus groups are characterized based on antigenic epitopes on which internal structure protein?

100

How many Orbivirus serotypes are there?

2

How many Coltivirus serotypes exist?

Immunofluorescence, ELISA, and immune electron microscopy (IEM)

List three methods used to detect Rotavirus.

VP4 and VP7

Rotavirus is classified based on which two outer capsid proteins?

VP7

Which rotavirus antigen is the predominant one?

Neutralizing activity

The epitopes on VP4 and VP7 are important for what clinical immune activity?

G1–G4 and G9

Which five predominant strains of rotavirus species A are responsible for the majority of human disease?

They differ geographically

How does the distribution of rotavirus serotypes vary?

Endoplasmic reticulum

In addition to the cytoplasm, which organelle plays a major role in rotavirus replication and morphogenesis?

Jawetz, Melnick, & Adelberg's Medical Microbiology

Which textbook is specifically noted for its diagram on rotavirus replication?

Villi of the small intestine

Where exactly in the GI tract do rotaviruses infect cells?

Damage to transport mechanisms

What happens to enterocytes when rotaviruses multiply in their cytoplasm?

NSP4

Which rotavirus-encoded protein acts as a viral enterotoxin?

Stimulating a calcium-dependent signal transduction pathway

What is the specific physiological mechanism of the NSP4 enterotoxin?

Osmotic and watery diarrhea

The sloughing of damaged intestinal cells into the lumen leads to which type of diarrhea?

10^12 particles per gram

What is the peak concentration of rotavirus particles in the feces?

2 to 12 days

What is the typical duration of viral excretion in a healthy person with rotavirus?

Poor nutrition and immunocompromised status

In which patients might viral excretion of rotavirus be prolonged?

Sodium and glucose absorption

Rotavirus diarrhea can be caused by the impairment of which two absorption processes?

Immature crypt cells

Damaged cells on the villi are replaced by what kind of non-absorbing cells?

3 to 8 weeks

How long does it take for normal intestinal function to be restored after rotavirus damage?

Gastric and colonic mucosa

Which parts of the GI tract are spared during a rotavirus infection?

1–3 days

What is the incubation period for rotavirus?

Watery diarrhea, fever, abdominal pain, and vomiting

What are the four main clinical symptoms of rotavirus?

Dehydration

What is the major clinical risk resulting from rotavirus symptoms?

Electrolytes and fluid

Severe loss of what two components can be fatal for infants with rotavirus?

3–8 days

In milder cases, how long do rotavirus symptoms persist before recovery?

50 days

Viral excretion of rotavirus can persist for up to how many days after the onset of diarrhea?

Pediatric cases

What is the most common source of rotavirus contact for adults?

Geriatric wards

In what specific setting do epidemics of severe rotavirus disease usually occur in closed populations?

Rise in antibody titer

Besides demonstration of the virus in stool, what else is required for a rotavirus laboratory diagnosis?

EIA (Enzyme immunoassay) and PCR

Which two methods are used for stool examination to diagnose rotavirus?

Winter

During which season does rotavirus gastroenteritis predominate in temperate climates?

Fecal-oral route

What is the primary mode of transmission for rotavirus?

6 months to 2 years old

In which age range does symptomatic rotavirus infection typically occur in children?

Maternal antibody acquired passively

Why are asymptomatic infections common in infants before age 6 months?

It does not prevent reinfection

Does a neonatal rotavirus infection prevent future infections?

It protects against severe disease during reinfection

What is the primary benefit of neonatal rotavirus infection regarding future immunity?

90%

By age 3, what percentage of children have serum antibodies to one or more rotavirus types?

Subclinical reinfections

What does the high prevalence of rotavirus antibodies in adults suggest?

5

By age 2, how many rotavirus reinfections might a young child suffer?

IgA and interferon

Which two local immune factors may be important in protection against rotavirus?

Supportive treatment

What is the only treatment available for rotavirus?

Restoring fluid and electrolyte balance

What is the primary goal of supportive treatment in rotavirus?

Intussusception

Why was the oral live attenuated rotavirus vaccine withdrawn in 1999?

Monovalent human and Pentavalent human-bovine reassortant

Which two types of rotavirus vaccines developed in 2008 are still in use?

Noroviruses

What are the most significant members of the Calicivirus family?

Norwalk virus

What is the prototype virus for Noroviruses?

Icosahedral

What is the virion shape of Caliciviruses?

27–40 nm

What is the diameter of a Calicivirus virion?

Cup-like depressions

What distinctive feature is found on the capsid surface of Caliciviruses?

(+)ssRNA (Positive-sense single-stranded RNA)

What is the genetic composition of the Calicivirus genome?

Linear and non-segmented

Describe the physical structure of the Calicivirus genome.

7.4–8.3 kb

What is the genome size of the Calicivirus family?

VPg (Genome-linked protein)

Which specific protein is contained within the Calicivirus genome?

Single protein

What is the capsid of a Calicivirus composed of?

Non-cultivable

Can human Caliciviruses be cultivated in a laboratory setting?

5

The Calicivirus family is divided into how many genera?

Norovirus, Sapovirus, Nebovirus, Lagovirus, and Vesivirus

List the five genera of the Calicivirus family.

Norovirus and Sapovirus

Which two Calicivirus genera contain human viruses?

Lagovirus and Vesivirus

Which two Calicivirus genera contain animal strains that can be grown in vitro?

Lagovirus

Which genus was introduced in Australia as a biological control agent for rabbits?

GI, GII, and GIV

Which three Calicivirus genogroups are associated with human gastroenteritis?

GII.4

Which genotype has caused most viral gastroenteritis outbreaks worldwide since 2001?

Antigetic drift

What process do Noroviruses undergo in response to population immunity?

Histo-blood group antigens

What are the receptors for Noroviruses expressed on mucosal epithelia?