Lecture 89: viral causes of diarrhea

Question 1

what are the primary viral causes of diarrhea?

which is the most common cause of diarrhea in kids < 5 worldwide?

Which is the most common cause of GI outbreaks?

Answer 1

Rotovirus
Calcivirus – Noro and sapovirus
Enteric Adenovirus- Serotypes 40 and 41
Astrovirus

< 5: Rotavirus

Outbreaks: Norovirus

Question 2

What is the common clinical presentation to the diarrheal viral illness?

what are some complications ?

Answer 2

Vomiting 
Watery Diarrhea 
No Gross blood 
No fecal lueukocytes 
Low grade Fever 

Complications: Dehydration, electrolyte abnormalities, lactic acidosis

Question 3

Rotavirus

• describe the virology – whats unique?
• what is the most pathogenic serotype to humans?
• distinct EM appearance?

Answer 3

Reoviridae -
Nonenveloped
Outer capsid, Inner capsid, viral core

“wheel with spokes” on EM

11 segments of ds RNA
- each segment encodes a unique protein

• GP18 – most pathogenic serotype

Question 4

Rotavirus -

describe the important proteins/antigens and its life cycle/pathogenesis

Answer 4

• VP7/VP4 - outer capsid proteins important for neutralization by antibodies

VP6 – Inner capsid protein important for immunoassay \

NSP4 – Enterotoxin

Lifecycle: protease cleaves VP7 activating the virus for attachment via the Spike - VP4.

Release core into cytoplasm for replication and protein synthesis

Inner capsid buds into ER

Release by Lysis

Pathogenesis: blunting of microvilli; malabsorption; increased secretions

Question 5

Rotavirus

• how is it transmitted ?
• Diagnosis
• Treatment
• Prevention

Answer 5

Non eveloped – therefore Hardy - transmitted in stool; fomites; respiratory;

Dx : VP6 immunoassay

Treat: Supportive

Prevent: attenuated pentavalent and monvalent forms

Question 6

Enteric Adenovirus

• which adenovirus serotypes?
• Virology

transmission

Answer 6

serotypes 40 & 41 are enteric

Noneveloped
Double stranded DNA ;

Trasmission: person to person

Question 7

Astrovirus

• virology
• distinct EM appearance

Answer 7

non enveloped
SS RNA, Positive sense

On EM: 5-6 pointed star with smooth surface

Question 8

Calciviridae –
Virology?
which genera are enteric pathogens?
Epi

Answer 8

Non Eveloped
ssRNA, positive sense

Norovirus – most common cause of GI outbreaks

23 million infections per year in the US. Cruise ship outbreaks

Very low infectious dose

Question 9

calciviridae -
Immunity:
who is susceptible ?

Answer 9

Very low infectious dose

Repeat infections due to enormous diversity of strains

Lack of long term immunity

Individuals of group O are more susceptible