What is norovirus?

Norovirus is a virus that causes gastroenteritis but usually resolves itself within 1 to 2 days without treatment. It’s easily spread from person to person, so good hygiene practices are important to prevent others from becoming infected.

What causes norovirus?

Norovirus is the name of a group of viruses that causes the infection. Many viruses can cause gastroenteritis, and norovirus is one of the more common. It is highly contagious, and it spreads from an infected person when someone has contact with:

• the infected person's vomit or faeces (poo)
• their unwashed hands
• surfaces or objects they have touched
• food or water they have contaminated

Norovirus is particularly likely to cause illness in places such as healthcare and aged care facilities, restaurants, schools and cruise ships. These are closed environments where lots of people eat food prepared by others. One infected person can easily pass the infection to other people.

Norovirus is also known as ‘winter vomiting’ because it tends to peak in winter when people stay together indoors. Some other common names for norovirus infection are gastric flu, stomach flu and viral gastro.

What are the symptoms of norovirus?

The main symptoms of norovirus are:

• vomiting
• nausea
• diarrhoea
• cramp-like stomach pain
• low-grade fever
• muscle aches

Symptoms usually appear 1 or 2 days after infection, but they can develop as soon as 12 hours after. They usually last for 1 or 2 days and rarely cause long-term harm in people who are otherwise healthy.

Symptoms can be more severe and long-lasting in elderly people, young children and people with a compromised immune system. If you or someone you care for has a severe infection, they may need hospital care.

How is norovirus diagnosed?

Norovirus infection is usually diagnosed based on the symptoms. A formal diagnosis will require laboratory testing of a stool (poo) sample. Public health authorities sometimes request this to help control an outbreak of illness.

How is norovirus treated?

The best treatment for a norovirus infection is rest and avoiding dehydration from vomiting and diarrhoea. This is particularly important for the elderly and babies.

Keep hydrated by drinking plenty of fluids such as an oral rehydration solution which you can buy at a pharmacy.

Juice, soft drink and cordial are all high in sugar, which can make diarrhoea worse. If you don’t have a rehydration drink, you can have these drinks diluted:

• Juice or soft drink: mix 1 part drink to 4 parts water (for example, 40 ml of the drink with 160 ml water)
• Cordial: mix 1 part cordial to 20 parts water (for example, 5 ml cordial with 100 ml water) 

There is no medication or antibiotic available to treat norovirus. You should only use anti-vomiting or anti-diarrhoeal medications if your doctor has recommended them.

How is norovirus prevented?

Norovirus is highly contagious, so good hygiene is very important.

To help prevent infection:

• wash hands with soap and running water after using the toilet or changing nappies.
• wash hands with soap and water before eating or handling food.
• wash food before eating, especially oysters and shellfish, and fruits and vegetables.
• wash bedding and clothing if they are stained by diarrhoea or vomit.
• clean contaminated household surfaces and disinfect with a diluted bleach-based cleaner.
• clean contaminated soft furnishings or carpet with hot water and detergent followed by a steam clean.

If you have been infected, you will still be contagious for a couple of days after the diarrhoea or vomiting has stopped. You should stay away from work, or keep an infected child home from childcare or school, until 48 hours after such symptoms have disappeared.

There is no vaccine to prevent norovirus infection.

When to see a doctor

See your doctor if:

• the diarrhoea lasts for more than 2 days in an adult, or for more than 24 hours in a baby
• you get dehydrated
• you also have a fever
• you have severe pain in your abdomen or rectum
• the diarrhoea is bloody or black