Viral gastroenteritis is acute inflammation of the gastric lining and intestines. It is caused by enteropathogenic viruses. It causes an increased frequency of defecation lasting less than 2 weeks, and may be accompanied by nausea, vomiting, anorexia, abdominal cramps and fever.
🦠 Causative agents
The main pathogens that may cause gastroenteritis include:
- Rotavirus
- Norovirus
- Caliciviruses
- Astroviruses
- Enteric adenoviruses
Other pathogens may cause opportunistic infections in immunocompromised hosts, such as: HIV, CMV, HSV.
In this CCC, we will be focusing on the 2 most common causes of viral gastroenteritis which are rotavirus and norovirus.
Norovirus, also known as the winter vomiting bug is a genus encompassing non-encapsulated RNA viruses.
It is the most common cause of viral gastroenteritis during winter in the UK, accounting for 1 in 5 cases of gastroenteritis altogether.
Pathophysiology and transmission
The virus enters cells through host receptor-mediated endocytosis and replicates in the small intestine. It requires only 10-100 viral particles to cause an active infection, meaning it is highly contagious.
It is transmitted by:
- Faecal-oral route
- Respiratory droplets - that become aerosolised with vomit or when faeces/vomit is flushed.
- Fomites
- Direct contact
😷 Presentation
Symptoms develop very acutely within 12-24 hours of infection:
- Nausea and projectile vomiting
- Non-bloody diarrhoea
- Headaches
- Low-grade fever
- Myalgia
🔍 Investigations
Diagnosis is based on clinical history.
Stool viral culture may be used but is rarely necessary.
🧰 Management
🥇 It is self-limiting and symptoms disappear after 72 hours. However, we should emphasise the need for oral rehydration and electrolyte replenishment.
The infected individual should be isolated and good hand hygiene should be maintained to reduce transmission (soap and water is more effective then alcohol hand gel).
Rotavirus is the most common cause of gastroenteritis in children (another common cause is adenovirus).
Pathophysiology
It causes severe diarrhoea. The mechanism by which it causes diarrhoea is believed to be by impaired fluid absorption due to cell damage. After ingestion, rotavirus infects the mature enterocytes. The rate of death of rotavirus-infected mature villous enterocytes exceeds the rate of production of new enterocytes within the crypts. This leads to structural damage within the small bowel such as villous shortening and crypt hyperplasia as well as inflammatory infiltrates within the lamina propria.
Immature enterocytes are more secretory as opposed to absorptive. Due to the damage of the brush border by villi, there is decreased absorption. Therefore the osmotic potential of the lumen draws water in (osmotic diarrhoea). Rotavirus also produces an enterotoxin (NSP4) which results in calcium secretion into the lumen, and water follows (secretory diarrhoea).
Rotavirus also activates the chemoreceptor trigger zone (CTZ) → vomiting.
😷 Presentation
It has an incubation period of 1-3 days, however, symptoms may appear even 12 hours after exposure:
- Fever
- Vomiting - usually lasting 1-2 days.
- Diarrhoea - usually lasting 5-7 days.
The main risk for rotavirus is severe dehydration which can cause shock.
NICE recommends classifying patients as either normal, dehydrated or shocked as opposed to mild, moderate and severe.
Features of dehydration | Features of shock |
Decreased urine output | Decreased consciousness |
Skin colour unchanged | Cold extremities |
Warm extremities | Pale or mottled skin |
Altered responsiveness | Tachycardia |
Sunken eyes | Hypotension |
Dry mucous membranes | Prolonged capillary refill time |
Tachycardia | Weak peripheral pulses |
Normal BP | Tachypnoea |
Normal peripheral pulses | |
Tachypnoea | |
Normal capillary refill | |
Reduced skin turgor |
Features that may suggest hyponatraemic dehydration include:
- Jittery movements
- Hypertonia
- Hyperreflexia
- Convulsions
- Drowsiness or coma
🔍 Investigations
It is once again a clinical diagnosis.
NICE suggests a stool culture when there is:
- Suspicion of septicaemia
- Blood or mucus in the stool
- Immunocompromised child
🧰 Management
- If shock is suspected → IV rehydration.
- If there is no evidence of dehydration:
- Continue breastfeeding or other forms of milk feeding in babies.
- Encourage fluid intake
- Discourage fruit juices and carbonated drinks
- If dehydration is suspected:
- 50ml/kg low osmolality oral rehydration solution (ORS) over 4 hours.
- Continue breastfeeding