L35 Diarrheal viruses

Question 1

Most enteric viruses are enveloped/non-enveloped, and thus are more susceptive/resistant to disinfection by alcohol.

Answer 1

non-enveloped;

resistant

Question 2

All enteric viruses causes diarrhea. T/F. Why?

Answer 2

False
- they may disseminate via viremia > disease in other organs

e. g. Hepatitis A/E > acute hepatitis
e. g. Enterovirus: Hand Foot Mouth disease, meningitis, encephalitis

Question 3

Other than viral causes, list other causes of acute gastroenteritis.

Answer 3

1. Bacterial
   - Salmonella, Shigella, Campylobacter
2. Parasites
   - Giardia, Entamoeba histolytica
3. Drugs
   - motility disturbances
   - Irritable/inflammatory bowel disease (IBD)

Question 4

DDx for foodborne diarrhea (not viral)? (7)

Answer 4

1. Salmonella species
2. Campylobacter species
3. Shigella species
4. Bacillus cereus
5. Staphylococcus aureus
6. Clostridium perfringens
7. Escherichia coli O157 H7

Question 5

DDx for viral diarrhea? (4)

Answer 5

1. Rotavirus
2. Norovirus (Human caliciviruses)
3. Enteric adenovirus
4. Astrovirus

Question 6

DDx for parasitic diarrhea?

Answer 6

Immunosuppressed

1. Cryptosporidium species
2. Microsporidium species

Immunocompetent

3. Giardia lamblia
4. . Cryptosporidium species
5. . Cyclospora
6. . Entamoeba histolytica

Question 7

DDx for traveler’s diarhhea?

Invasive + Secretory (8)

Answer 7

Invasive

1. Shigella species
2. Enteroinvasive E.coli
3. E.coli O157:H7
4. Enteropathogenic E.coli
5. Salmonella species
6. Campylobacter species

Secretory

7. Vibrio cholera
8. Enterotoxigenic E.coli

Question 8

Rotavirus 
A. from Reoviridae 
B. non-enveloped 
C. dsDNA virus 
D. with 8 groups, Group A infect humans 
E. Minimal cross-species transmission

Answer 8

C is incorrect:

dsRNA virus

Question 9

What is the most common causative virus to viral gastroenteritis in young children and neonates?

At what ages patients are symptomatic?

Answer 9

Rotavirus

• > 6 months and <5 years old + > 60 years old
• Asymptomatic <6 months because of maternal IgA; >5 years old because already infected, produced immunity

Question 10

Rotavirus 
A. Male predominance
B. Winter peak 
C. Via faecal-oral route
D. Via respiratory route
E. 1-2 days of the incubation period and causes diarrhea of 4-7 days

Answer 10

D is wrong

• should be Norovirus
• Rotavirus only faecal-oral route

Question 11

What are the clinical presentations of Rotavirus infection?

Answer 11

Watery diarrhea
+/- vomitng, fever
> dehydration

Question 12

Treatment for Rotavirus-caused gastroenteritis?

Answer 12

Rehydration (oral/IV)

Question 13

Laboratory diagnosis for Rotavirus? (3)

Answer 13

Viral antigen detection

1. Enzyme immunoassay
2. Latex agglutination test

NOT

• PCR because the high load of viral shedding in stool, PCR is extremely sensitive
• EM because low throughput, technically demanding

Question 14

Prevention of Rotavirus?

Answer 14

Oral vaccination (live attenuated vaccines)

1. RotaRix: 2 doses, monovalent
2. RotaTeq: 3 doses, pentavalent

• 1st dose between 6-14 weeks of age, last dose before 32 weeks

Question 15

What are the contraindications of Rotavirus oral vaccine? (3)

Answer 15

1. C/I in severe combined immunodeficiency (SCID)// immunocompromised
2. Catch up vaccination not recommended: risk of intussusception
3. Not co-administered with oral Polio vaccine: both contain live virus&raquo_space;> increase GI motility > increase risk of intussusception

Question 16

Norovirus
A. Same family as sapovirus
B. ssRNA 
C. non-enveloped
D. is Winter vomiting disease
E. MC source is from poultry

Answer 16

E is wrong, should be from seafood - contaminated/ inadequate cookng
D: Winter, somtimes summer too;
Epidemic!

A: yes, both from Caliciviridae

Question 17

What is the MC cause of viral gastroenteritis in adults?

Answer 17

Norovirus

Question 18

What are the routes of transmission of Norovirus?

Answer 18

1. Fecal-oral route
   - human-to-human (80%)
   - Environment contamination

• Different outbreak patterns

2. Respiratory route
   - Inhalation of aerosols from feces/ vomitus

Question 19

Norovirus has short incubation: 0.5-3 days
Duration: 1-4 days
Clinical presentations of Norovirus-caused gastroenteritis? (2)

Treatment?

Answer 19

1. Projectile vomiting
2. Diarrhea +/- fever

• rehydration as treatment

Question 20

What is the laboratory diagnosis of Norovirus gastroenteritis?

Answer 20

RT-qPCR
- stool & rectal swabs (not vomitus)

NOT

1. EM: technically demanding
2. Viral Ag detection: not sensitive, for outbreak investigation only

Question 21

Prevention of Norovirus?

Answer 21

NO vaccination available

1. Hand hygiene - 1:99 bleach but not alcohol-based sanitizer (non-enveloped virus)
2. Wash and cook food thoroughly

Question 22

Enteric adenovirus
A. non-developed
B. dsDNA viruses
C. Types 40 and 41 are associated with GE
D. 2nd MC cause of GE in adults
E. Detected by Viral Ag detection by ELISA

Answer 22

D is incorrect

- should be 2nd MC of young children

Question 23

Astrovirus
A. Small RNA virus
B. causes endemic GE in young children and adults
C. 10% of GE in children
D. Use of an antigen detection assay for laboratory diagnosis
E. Star-shaped surface morphology, 28nm in diameter

Answer 23

D is incorrect

- No good antigen detection assay