Viral Gastroenteritis

Question 1

Viral gastroenteritis

Answer 1

common –> self-limiting infections that require supportive care
- fecal-to-oral transmission (human-human, animal-human)
- Secretory diarrhea –> infection damages proximal small bowel
- stool does not contain WBCs!!!!
MAJOR CAUSES
- Rotavirus –> seasonal (winter) and kids
- Norovirus –> non-seasonal, adults, outbreaks

Question 2

Rotavirus

Answer 2

RNA virus –> icosahedral –> nonenveloped –> DS, RNA segmented genome (class III) –> Reoviridae
- 10-12 segments –> can get reassortment
- VERY Stable in environment –> double-shelled
Hosts –> humans, vertebrates
Tropism –> mature absorptive villi of epithelium in small intestine (after replication, particles are released into lumen when the pH makes them mature and infectious)

Question 3

Infantile Gastroenteritis

Answer 3

50% rotavirus –> in U.S. it isn’t too serious

- outside U.S. where there isn’t access to healthcare/nutrition –> BAD mortality

Question 4

How does Rotavirus replicate?

Answer 4

It brings with EVERYTHING it needs for replication

• RNA polymerase, 5’ cap, etc
• release of virus from cell results in cell lysis and death –> virus becomes infectious again because of pH conditions in lumen of intestine

Question 5

Rotavirus – NSP4

Answer 5

NSP4 is a viral enterotoxin –> very unique for a virus because usually only bacteria have toxins
- this toxin disrupts the Ca flux between the ER lumen and cytoplasm causing the increased fluid flux into lumen and diarrhea

Question 6

Time-line for rotavirus

Answer 6

8 hrs post-infection you can already see cytoplasmic cellular inclusions
48-72 hrs post-infection = peak infection
- can get 10 billion viral particles per gram of stool

Question 7

Treatment in nutrition deficit places?

Answer 7

Patients will get rehydration therapy as well as a Vit A shot
- Vit A deficiencies have been shown to exacerbate the infections

Question 8

Rotavirus vaccines

Answer 8

Both vaccines are live-attenuated

- 1 is from humans (rotatrix), other is hybrid of human/cow (rotateq)

Question 9

Norovirus (norwalk)

Answer 9

RNA virus –> isocahedral –> nonenveloped –> SS(+) nonsegmented genome (IV) –> calciviridae –> calicivirus –> norwalk virus

• human-only pathogens with tropism for intestinal epithelial cells
• VERY INFECTIOUS, slows gastric emptying –> vomiting
• low fever
• 70% of kids have ABs against a strain, but strains have very high error rates in RNA polymerase –> mutations

Question 10

Strains of norovirus

Answer 10

Strains can mutate quickly because of error-prone RNA polymerase

• leading cause of gastroenteritis in U.S.
• “2-bucket” virus

Question 11

Adenovirus strains 40-42

Answer 11

DNA virus –> icosahedral –> nonenveloped –> DS linear DNA (I) –> adenoviridae

• only strains 40-42 can cause GI infections
• infants, young kids, immunocompromised
• prevent with handwashing, chlorination
• supportive care