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Flashcards in GI Tract Viral Infections Deck (15):
1

List the viruses associated with gastroenteritis.

Enteroviruses (Picornaviridae) = not major cause of diarrhea:
o Poliovirus
o Coxsackie viruses
o Echoviruses (Enteric Cytopathic Human Orphan virus)
o Enterovirus

Gastroenteritis agents = primary symptom is diarrhea
o Caliciviruses/Norovirus = 20-30% infections in U.S.
o Rotaviruses
o Adenoviruses = 5-15% infections in U.S.
o Astroviruses = 20-30% infections in U.S.
o Coronaviruses = ~10% infections in U.S.

2

Caliciviruses/Norovirus

20-30% infections in U.S.
• Acute gastroenteritis in kids and adults
• No seasonal variation
• Usually seen as explosive outbreaks in institutions/communities (very infectious)

3

Rotaviruses

•• Acute gastroenteritis in kids less than 2 and adults
• Peak incidence = winter (“Winter Diarrhea”)
• 90% people over 4 yrs are seropositive

4

Adenoviruses

5-15% infections in U.S.
• Primarily in infants and children
• No seasonal outbreaks
• Usually sporadic outbreaks

5

Astroviruses

20-30% infections in U.S.
• Acute gastroenteritis in kids
• 75% of kids ages 3-4 are seropositive
• Higher incidence in winter

6

Coronaviruses

~10% infections in U.S.
• Most frequent in kids <1 year
• Diarrhea can be associated with respiratory coronavirus infection
• SARS CoV or colds in children and adults
• Diarrhea = often has blood, less watery, and mucoid

7

Describe the major mechanism for the causation of diarrhea by Rotaviruses and Astroviruses.

Overall = gastroenteritis agents:
o Little to none intestinal inflammation or cell death
o Some shortening of microvilli → maladsorption

Rotavirus
o Viral toxin = NS4 protein
o Activates adenylate cyclase

Astrovirus
o Viral toxin = capsid
o Alters actin cytoskeleton → opens cell-cell junctions
• Note: for both rotavirus and astrovirus = can detect virus systemically, but symptoms are restricted to GI tract

8

Describe the mechanisms of transmission for the gastroenteritis agents

Primary mode of spread = fecal-oral
• Shed in large amounts from GI tract
• Shedding can last for weeks after symptoms

o Noroviruses = also have airbourne transmission
o Astroviruses = can be spread by vomitus
o Resistant to low pH

Incubation period = usually 1-3 days

Symptoms:
• Abrupt onset: vomiting, diarrhea, intestinal cramping
• May also have headache, myalgia, and low grade fever
• Watery diarrhea; usually no blood or mucus
• Exception = Coronaviruses

9

Name the most important therapeutic measure for gastroenteritis.

Prevention
o Hand washing
o Clean water; non-contaminated food

Supportive
o Maintain proper hydration
o Do not use agents that reduce peristalsis of gut (because infectious diarrhea)

Vaccine for Rotavirus
Part of routine infant immunizations
• Given at 2, 4, and 6 months
• Minimum age of 1st dose = 6 weeks
• 1st dose should be given at 6-12 weeks (until age 13 weeks)
• Do NOT initiate series after 12 weeks
Do NOT give if:
• Altered immunocompetence
• Recent blood product recipient
• Acute, moderate to severe gastroenteritis or other acute illness
• Pre-existing chronic GI disease
• Infants with history of intussusception

10

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

• Diarrhea can have blood or mucus
• Appears to cause inflammatory condition

11

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

Multiply to high titers in GI tract
o Shed in feces even after symptoms gone
o Fecal-oral route

Cause disseminated infections in host
o Frequently = mild or asymptomatc

Stable at pH 3.0

Very hardy = can survive 70% ethanol, 5% Lysol, 1% detergents

Sensitive to 0.3% formaldehyde; 0.3-0.5 ppm chlorine

Inactivated at 50°C

12

Characteristics of polio virus

o Typical disseminated pattern
o About 2 week incubation

Usually causes aseptic meningitis or subclinical infection
• Invades CNS in 1-2% of infections
• Replicates in motor neurons (in anterior horn of spinal column, brain stem, motor cortex)
• Death of neurons → paralysis
• Occurs more frequently when primary infection occurs as teen or young adult

Patient death = usually due to paralysis of diaphragm and respiratory muscles → suffocation

Surviving patients usually regain some function in affected limb
• “Post-polio syndrome” = masks mild paralysis

13

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

Vaccines:
Salk vaccine
• Inactivated virus (contains all 3 serotypes)
• Currently recommended

Sabin vaccine
• Live attenuated virus (contains all 3 serotypes)
• Can revert to virulence = most common with Type 3 strain → cause infection
• Currently not recommended in U.S.


14

Describe the Hepatitis A vaccine

o Inactivated whole virus
o Pediatric and adult formulations
• Approved for patients ≥12 months

Recommended for:
• International travelers
• Men who have sex with men
• Persons who use illegal drugs
• Persons with occupational risk
• Persons with chronic liver disease

15

List the major disease syndromes caused by enteroviruses

Mild self-limiting illness with rash
• Exception = polio
Colds
Aseptic meningitis
Pericarditis/myocarditis
• Coxsackie viruses
Paralysis
• Polio = can cause lethal paralysis
Hepatitis