Norovirus

Norovirus is a very common virus that causes gastroenteritis (inflammation of the stomach and intestines).

Common names used for gastroenteritis due to norovirus are:

• gastric flu
• stomach flu
• winter vomiting
• viral gastro.

It is highly contagious and often causes outbreaks, particularly in aged care facilities, childcare centres, schools and hospitals. Outbreaks can occur at any time of the year but are more common during winter and into spring.

Symptoms

Illness caused by norovirus usually starts suddenly and causes vomiting and diarrhoea. Vomiting can be frequent and is more common in children.

Other symptoms may include:

• nausea
• abdominal pain
• muscle aches
• headaches
• tiredness
• mild fever.

Symptoms of norovirus illness usually begin about 24 to 48 hours after ingestion of the virus, but they can appear as early as 12 hours after exposure. Illness generally lasts for one to three days. Dehydration is the most common complication of norovirus gastroenteritis.

How norovirus is spread

Norovirus is highly infectious and is spread from the vomit or faeces of an infected person. People are usually infectious from when their symptoms start until at least two days (48 hours) after the symptoms stop.

You become ill by accidentally taking in the virus through your mouth, which happens when your hands have small amounts of faeces (stools, poo) or vomit from an unwell person.

This can occur through:

• close person-to-person contact, for example shaking hands with someone who has been sick and has the virus on their hands
• direct contact with the vomit or faeces of an infected person
• contact with contaminated objects or surfaces (such as door and tap handles)
• consuming contaminated food or drink (often contaminated as a result of poor food handling or poor hand washing).

Infection can also be spread in the air when people vomit or consuming oysters or other shellfish that have been contaminated with norovirus.

Who is at risk of infection

Norovirus can affect anyone. The illness is generally mild but if people are unable to drink enough fluids to replace what they lose through vomiting and diarrhoea, dehydration can become a problem. Infants, young children, older people and people with disability are at greatest risk of dehydration.

Diagnosis

Diagnosis is based on a person’s symptoms and testing is not usually required. During outbreaks, it may be important to do testing to identify exactly what is causing people’s illness in order to guide public health responses (and exclude non-viral causes). This involves testing samples of faeces.

Treatment

People with norovirus infection should rest and ensure they drink enough fluids. Most people will recover without complications. Oral rehydration solutions (available from the chemist) are specially formulated to rapidly replace lost fluid and maintain electrolyte (salts) balance.

Norovirus infection can be serious for those who have difficulty replacing fluids and salts lost through vomiting and diarrhoea. Antibiotics will not help, because they fight bacteria, not viruses like norovirus.

Prevention

The most effective way of preventing norovirus gastroenteritis is to practice good hand washing. This is achieved by washing hands thoroughly using soap and running water for at least 30 seconds, followed by drying hands with a clean towel.

This should be done before preparing food and before eating, after using the toilet, after changing nappies, after assisting someone with diarrhoea and/or vomiting, and after cleaning up body fluid spills.

While you have gastroenteritis symptoms, and for the 48 hours after the symptoms have resolved, it is important to keep your hands clean by washing them often and thoroughly.

You should also avoid preparing food for people during this time. Immediately remove and wash any clothes or bedding contaminated with vomit or diarrhoea using detergent and hot water.

Clean contaminated surfaces (for example benches, floors and toilets) immediately using detergent and hot water. Then disinfect surfaces using a bleach-based product diluted according to the manufacturer’s instructions.

Staying home from school or work

Anyone with vomiting or diarrhoea should rest at home and not attend work, school or childcare, or visit a hospital or residential care facility, until vomiting and diarrhoea have stopped for 48 hours. During this time they should not prepare food for others, or care for patients, children or the elderly.

Outbreaks

Outbreaks of norovirus gastroenteritis increase during winter and are common in settings such as aged care facilities, childcare centres and hospitals.

Under the Public Health Act 1997, outbreaks of two or more cases of vomiting and/or diarrhoea in 24 hours should be notified to the Health Protection Service. Health protection service staff will be able to provide advice on controlling the outbreak.

More information

For more information about norovirus, contact your GP or call the Health Protection Service, Communicable Disease Control Information Line during business hours on (02) 5124 9213.

Acknowledgement

Heymann DL, 2015, Control of Communicable Diseases Manual, 20th edition. Centers for Disease Control and Prevention, Norovirus, 2018.