Virology 6 Enteric Infections

Question 1

1. List the viruses associated with gastroenteritis.

Answer 1

Group 1: enteroviruses
Group 2: viruses whose primary disease syndrome is diarrhea

(within the picornaviridae are small non-enveloped RNA viruses: polio viruses, enteroviruses, coxsackie viruses and echoviruses)

Question 2

2. Describe the major mechanisms for the causation of diarrhea by Rotavirus and Astroviruses.

Answer 2

pathophysiologically little or no inflammation or cell necrosis in the gut wall, shortening of the microvilli was seen (loss of absorptive process)– one of the non-structural proteins of (rotavirus) turns out to be a toxin and acts in a manner similar to cholera toxin, the capsid protein of Astrovirus, and the same might be expected from Norovirus or Adenovirus

Question 3

3. Describe the mechanisms of transmission for the viruses listed in the outline.

Answer 3

fecal oral transmission

Question 4

4. Name the most important therapeutic measure for gastroenteritis.

Answer 4

prevent dehydration

Question 5

5. Coronavirus diarrhea is different from other gastroenteritis viruses. What does this imply for the pathogenesis of the infection.

Answer 5

gastroenteritis caused by coronavirus is most commonly seen in children under 1 year of age and diarrhea can include occult blood, less watery and more mucoid (not seasonal); appears to cause an inflammatory condition based on blood and mucous in stool

Question 6

6. Describe and differentiate between the symptoms caused by the viruses associated with gastroenteritis.

Answer 6

polio, enteroviruses, coxsackie viruses and echoviruses do not normally cause the symptoms of diarrhea (rashes (except polio), aseptic meningitis, pericarditis/myocarditis, paralysis, hepatitis, colds)

viruses including rotavirus, noroviruses and astroviruses as well as adenoviruses and coronaviruses (have subtypes) that have diarrhea dan vomiting as the primary symptoms of infection

Question 7

7. Describe the mechanism of pathogenesis for enteroviruses. What factor is critical for CNS invasion resulting in meningitis or paralysis?

Answer 7

acquired by the fecal-oral route and replicates in the gut mucosa, it enters the body through Peyer’s patches and M cells in the gut, CNS involvement requires high titer and persistent secondary viremia

Question 8

8. Explain how polio is currently prevented and why the oral polio vaccine is no longer used in the United States.

Answer 8

polio is currently prevented by vaccine, the oral vaccine is easy to administer but is not used in the US because it is possible for the vaccine to revert back to the wild type virus and cause disease (vaccine was causing more cases than wild type in US)

Question 9

9. List the major disease syndromes caused by enteroviruses and which virus is associated with each disease.

Answer 9

rashes (except polio)
aseptic meningitis
pericarditis/myocarditis
paralysis
hepatitis
colds

(coxsackie virus are frequently involved in myocarditis)
a high percentage of infections are asymptomatic especially in childhood

Question 10

Discuss general characteristics regarding spread of Enteroviruses.

Answer 10

spread oral-fecal route: are acid stable, resist alcohols, Lysols and detergents (formaldehyde and chlorine is used to inactivate them

Question 11

What is the normal course for enterovirus diagnosis and treatment.

Answer 11

diagnosis is based on clinical symptoms, treatment is primarily dealing with patients’ symptoms and providing support (prevent with good hygiene and proper chlorination)

vaccination is the best available preventative strategy if vaccines are available (only hep A and polio currently)

Question 12

Name the most prevalent/important causes of diarrheal illness in the U.S.

Answer 12

rotavirus was the most common (was before vaccine)
noroviruses: second or third most important cause of diarrheal illness in the U.S. overall and leading cause of hospitalization of infants in the U.S.

Astroviruses is the second or third most prevalent cause of viral gastroenteritis

Question 13

Discuss differential symptoms that can help to determine which enterovirus maybe the cause of infection.

Answer 13

rotavirus: underdeveloped countries
norovirus: communal environments, vomiting is a common occurrence, low fever
astroviruses: last 2-4 days, vomiting is less common, fever is not common, higher incidence in winter (shedding continues after symptoms)
adenovirus: low grade fever possible, NOT seasonal