Viral gastroenteritis

Question 1

What is gastroenteritis?

Answer 1

infective illness which causes diarrhoea, vomiting and often abdominal pain. The majority of cases are viral, and a smaller percentage are true “food poisoning” (usually bacterial, occasionally parasitic) related to improper preparation or storage of food.

Question 2

When does gastroenteritis typically occur?

Answer 2

It typically occurs in outbreaks in winter (often rotavirus or norovirus – “winter vomiting virus”), and may cause hospital wards to be shut down during an outbreak.

Question 3

What are the two most common viruses behind viral gastroenteritis?

Answer 3

1. Rotavirus
2. Norovirus

Question 4

Describe the genetic composition of rotavirus:

Answer 4

double stranded RNA

Question 4

What age group does rotavirus typically affect most?

Answer 4

infants

Question 5

Give 5 symptoms of viral gastroenteritis:

Answer 5

1) vomiting
2) fever
3) diarrhoea
4) metabolic consequences of water and electrolyte loss
5) crampy abdominal pain

Question 6

What mode of transmission is seen in rotavirus infection?

Answer 6

faecal oral (viruses shed into faeces)

Question 7

What is the name of the rotavirus oral vaccine?

Answer 7

rotarix

Question 8

Describe the pathophysiology of viral gastroenteritis:

Answer 8

1) the virus uses the enterocytes of the intestines to replicate which leads to breakdown at the brush boarder meaning less enzymes are produced - resulting in malabsorption and hence osmotic diarrhoea
2) viral toxins directly damage cells, causing cell lysis as well as fluid loss from the intestine

Question 9

What are the risk factors for gastroenteritis?

Answer 9

Poor sanitation / poor personal hygiene
Immunocompromised patients
Poor food preparation
Undercooked
Reheated – reheating food correctly will kill bacteria, but will not destroy any toxins they left behind
Left at room temperature for too long
Particularly at risk foods include seafood

Question 10

Aside from rotavirus and noravirus what other viral causes are there?

Answer 10

1. Adenovirus (young children)
2. Enterovirus
3. Ebola

Question 11

What are the typical incubation periods for gastroenteritis?

Answer 11

Virus – 1 day
Bacterial – hours to days (up to 4 days)
Parasite – 7-10 days

Question 12

What are the clinical presentations of gastroenteritis?

Answer 12

Diarrhoea – often watery – multiple episodes – up to 10x per day is not unusual
Vomiting – again can be frequent – up to 10x daily

Children are more likely to be febrile with an infective gastroenteritis
In adults, fever may be indicative of a more serious cause

Question 13

What are 9 differential diagnoses?

Answer 13

1. UTI
2. Appendicitis
3. diverticulitis
4. pancreatitis
5. IBD
6. Constipation
7. Gastritis
8. Addisons disease
9. Type 1 diabetes

Question 14

When should stool samples be performed?

Answer 14

Blood or mucus in the stool
Patient known to be immunocompromised
Symptoms not resolving after 7 days
Recent overseas travel
Any uncertainty about diagnosis

Question 15

Give 5 diagnostic techniques for rotavirus gastroenteritis:

Answer 15

1) clinical diagnosis (most patients do not warrant further testing)
2) genome amplification
3) ELISA detection of the virus antigen in faeces
4) electron microscopy of the faeces
5) histology of jejunal mucosa

Question 16

Describe 3 changes to the jejunal mucosa seen on histology in children with rotavirus gastroenteritis:

Answer 16

1) shortening of villi
2) crypt hyperplasia
3) mononuclear cell infiltration of the lamina propria

note: this is similar to Coeliac histology - use the history to differentiate (acute/chronic)

Question 17

How is viral gastroenteritis treated?

Answer 17

symptomatic management - maintaining hydration and countering electrolyte loss

Question 18

Give two modes of transmission used by norovirus:

Answer 18

1) faecal oral
2) aerosol (norovirus is detected in vomit particles)

Question 19

How long do episodes of norovirus gastroenteritis last?

Answer 19

12-48 hours

Question 20

Give 3 diagnostic methods for norovirus gastroenteritis:

Answer 20

1) clinical diagnosis (most patients do not warrant further testing)
2) antigen testing in faeces
3) detected of viral nucleic acids in faeces