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 spreads

Norovirus is highly infectious and very few virus particles are necessary to cause infection.

It can spread:

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

Who is at risk

All age groups may be affected by norovirus.

Symptoms

Symptoms usually develop between 24 and 48 hours after exposure. But may occur as early as 12 hours after.

It can cause sudden onset of profuse vomiting and watery diarrhoea, and stomach cramps.

Other symptoms may include fever, headache and muscle aches.

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

Dehydration is the most common complication, especially among the very young and the elderly.

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.

Due to this long infectious period, it is important to use good hand washing and other hygienic practices after infection.

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

Treatment

There is no medication that specifically treats norovirus infections.

Treatment mainly focuses on preventing and treating dehydration caused by vomiting or diarrhoea.

To avoid dehydration, anyone with vomiting or diarrhoea should drink extra fluids.

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.

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

When to see a doctor

Children who refuse extra fluids should see a doctor.

Additionally, anyone with the following should also see a doctor:

• prolonged (>3 days) or severe diarrhoea
• blood in their stools
• people concerned about their symptoms.

Control measures

People with vomiting or diarrhoea should not:

• prepare or handle food that will be eaten by others
• go back to work, school or childcare until 48 hours after diarrhoea and vomiting have ceased
• 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 in a group, these should be reported to the local Centre for Disease Control.

Prevention

There is no vaccination against norovirus. Good hygiene is important in limiting the spread.

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 should be cleaned thoroughly with a bleach-based product diluted 1 in 10 with water.

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

Information for health professionals

To find out more, go to the NT Health website.

Contact

Contact your nearest Centre for Disease Control on the NT Health website.