Norovirus

Norovirus is a virus that can cause infection of the gastrointestinal tract. It has been known previously as the ‘Norwalk virus’, ’winter diarrhoea’ and winter vomiting disease’ although it occurs all year round.

How it is spread

Norovirus is highly infectious. Very few virus particles are necessary to cause infection, and outbreaks have commonly occurred in aged care facilities, cruise ships and tour buses where people are living and travelling in close quarters.

Norovirus can spread by eating food or drinking water that has been contaminated by very small amounts of vomit or faeces from infected people.

It can also be spread via direct contact with an infected person or via contaminated surfaces. Raw or undercooked seafood, such as oysters, have also been a source of infection.

Symptoms

Norovirus infection causes sudden onset of profuse vomiting and/or watery diarrhoea and stomach cramps. Other symptoms may include fever, headache and muscle aches. Symptoms usually develop between 24 and 48 hours after ingestion of the virus, but may occur as early as 12 hours after exposure.

The illness is usually self-limiting, with recovery being complete within 72 hours of onset of symptoms.

Infectious period

People are infectious to others from the moment they are ill until 48 hours after symptoms have stopped. In some cases, a person can still be infectious up to 2 weeks after recovery. Because of this long infectious period, it is particularly important to use good hand washing and other hygienic practices after norovirus infection.

There is no evidence that an infected person can become a long-term carrier of norovirus.

Who is at risk

All age groups may be affected by norovirus. Dehydration is the most common complication, especially amongst the very young and the elderly.

An episode of norovirus infection does not cause a person to be immune from norovirus for life. Therefore people may get sick if infected again on another occasion. There is no vaccination against norovirus.

Treatment

There is no medication that specifically treats norovirus infections. Management focuses on preventing and treating dehydration caused by vomiting or diarrhoea.

Anyone with vomiting or diarrhoea should drink extra fluids to avoid dehydration. Rehydration therapy with oral glucose/electrolyte solution is particularly effective.

If children refuse this solution, diluted fruit juice may be given (1 part juice to 4 parts water).

Babies should continue to be offered their normal feeds plus extra fluids in between feeds.

Children with diarrhoea, who vomit or who refuse extra fluids should see a doctor.  Anyone with prolonged or severe diarrhoea, or who have symptoms that cause concern, should see a doctor.

Medicines to prevent vomiting or diarrhoea should not be given, especially to children, except where prescribed by a doctor.

Prevention

Good hygiene is important in limiting the spread of norovirus. Hands should be washed thoroughly with warm soapy water, particularly:

• after going to the toilet
• before preparing or handling food
• after every nappy change
• after touching soiled linen or clothing.

Surfaces that may be contaminated (bathrooms, bench tops etc.) should be cleaned thoroughly with a bleach-based product diluted 1 in 10 with water.

Cooking oysters thoroughly before eating them will reduce the risk of infection.

How it can be controlled

People with vomiting or diarrhoea should not prepare or handle food that will be eaten by others.

Health care workers and food handlers should not go back to work until 48 hours after diarrhoea and vomiting have ceased.

Children should be excluded from childcare/school until 48 hours after diarrhoea and vomiting have ceased.

Anyone with diarrhoea should not swim, wade or paddle in public pools.

Doctors and public health workers are interested in preventing outbreaks of diarrhoea. If there are 2 or more cases of diarrhoea in a group, these should be reported to the local Centre for Disease Control.

Information for health professionals

To find out more go to the NT Health website.

Contact

For more information contact your nearest Centre for Disease Control.