Norovirus Stomach flu

What is Norovirus?

Norovirus and Norwalk virus belong to a group of very similar viruses called Norwalk agents, Norwalk-like agents, Noroviruses, etc. that cause an acute diarrhoeal illness. Gastro-intestinal illness with nausea, vomiting and diarrhoea may be caused by many viruses.  The Norwalk-like agents, Norovirus, etc. are one group of viruses that can cause this illness.

How do you get Norovirus?

These viruses are transmitted from person to person through direct contact with a sick person and poor personal hygiene. These viruses may persist in the environment (e.g., on door knobs, stair railings, etc.) where they come in contact with hands and are then transferred to the mouth.

Human-to-human transmission through personal contact is common. People are infectious during the acute phase of the illness and perhaps up to 48 hours after the diarrhoea stops.

In hospital settings, these viruses are sometimes transmitted by inhaling respiratory droplets coughed into the air by patients.

Susceptibility and Resistance

Most people are susceptible since immunity after the illness is usually short-lived (up to 14 weeks).


Incubation Period

The incubation period for Norovirus is 1-2 days.

What are the Symptoms?

Infection with this group of viruses is usually a mild to moderate self-limiting illness characterized by the rapid onset of nausea, vomiting and diarrhoea.  Abdominal pain, muscle aches, headache and fatigue may also be present with a slight fever.  The symptoms usually last 24-48 hours. 

Preventative Measures

Good personal hygiene and hand washing are the best preventive measures. If in contact with anyone with vomiting and diarrhoea, immediate hand washing is advised.


There is no specific treatment other than symptom relief and maintenance of adequate intake of fluids.  Antibiotics are not effective for treating infections caused by viruses like Norwalk.  

Where Does It Commonly Occur?

Noroviruses can occur anywhere in the world in both developed and developing countries.