The norovirus is shed in the stools (faeces) of infected people and animals. The main methods of transmission are:
- Eating contaminated food
- Drinking contaminated water
- Hand-to-mouth contact after handling a contaminated surface or object
- Close contact with a person who has a norovirus infection, eg: sharing food and cutlery
- Through the air — vomiting can send tiny particles into the air.
The norovirus is difficult to kill. In can withstand exposure to hot and cold temperatures as well as most disinfectants.
Norovirus infection commonly occurs in closed and crowded environments, eg: hospitals, nursing homes, aged-care facilities, schools, hotels, and cruise ships. The infection of a group of people in the same place and time is called an outbreak.
Signs and symptoms
Signs and symptoms of norovirus infection include:
- Abdominal pain or cramps
- Diarrhoea (loose or watery stools)
- Generally feeling unwell
- Mild fever; chills
- Muscle aches and pain.
Symptoms, especially diarrhoea, abdominal pain, and vomiting typically begin 24–48 hours after exposure to the virus and last 1–3 days.
Medical attention should be sought if the diarrhoea does not go away within several days, or if bloody vomit or stools, severe abdominal pain, or dehydration are experienced.
People are infectious for at least 3 days after recovery and in some cases for up to 2 weeks.
Some people may show no signs or symptoms; however, they are still contagious and can spread the virus to others.
Diagnosis of norovirus infection is usually based on symptoms. Infection can be confirmed by testing a stool sample for the presence of norovirus.
There is no specific medical treatment for norovirus infection. Most people recover completely without treatment.
Recovery is dependent on the health of a person’s immune system. People with an immature or weak immune system — especially infants, the elderly, and people with underlying disease — can become severely dehydrated and require medical attention, primarily fluid replacement.
Unless otherwise instructed by a GP, anti-diarrhoeal medications (to slow the diarrhoea) and anti-nausea medications (to reduce the nausea) should be avoided. In most cases, it is better to let the body clear itself of the virus.
Use of antibiotics should be avoided because they are not effective against viruses and their inappropriate use contributes to the development of antibiotic resistance.
Drink plenty of fluids, such as plain water, over-the-counter oral hydration solutions, sports drinks, and home-made broths to help to prevent dehydration.
Drinking beverages with high sugar content, such as soft drinks and fruit juices, should be avoided as they can make diarrhoea worse.
Smaller meal portions and a bland diet (e.g. soup, noodles, rice, or crackers, broiled vegetables) may help limit vomiting.
In some people - notably infants, the elderly, and people with an existing illness - norovirus infection can cause severe dehydration, malnutrition, and possibly death.
Dehydration is the main cause of serious illness. Typical signs and symptoms of dehydration include:
- Dry mouth and throat
- No tears, sunken eyes, sunken fontanelle in infants
- Lethargy, dizziness, cool hands and feet or grey cold skin
- Little or no urine passed in the previous 8 hours
- Skin that does not relax after being pinched
- Urine that is dark and smelly
Dehydration in anyone, especially infants and children, the elderly, and people with weakened immune systems, is a reason to contact a doctor immediately.
To help prevent becoming infected with norovirus and spreading it once infected:
- Wash hands frequently and thoroughly with soap and water or an alcohol-based gel, especially before eating or preparing food and after using the toilet or changing a nappy
- Avoid preparing or handling food for at least 48 hours after the symptoms stop
- Avoid contact with people who have symptoms of diarrhoea and vomiting
- Avoid consuming contaminated food and water, including food that may have been prepared by someone who was sick
- Wash fruits and vegetables before eating
- Cook seafood thoroughly
- Dispose of vomit and faecal matter carefully, to avoid spreading norovirus by air
- Disinfect contaminated surfaces with a chlorine bleach solution wearing gloves
- Stay home from work and keep children away from school or day care
- Avoid traveling until signs and symptoms have ended.
Further information and support
Free phone: 0800 611 116
Free phone: 0800 933 922
Ministry of Health (2016). Norovirus (vomiting and diarrhoea bugs) [Web page]. Wellington: Ministry of Health. http://www.health.govt.nz/your-health/conditions-and-treatments/diseases-and-illnesses/norovirus-vomiting-and-diarrhoea-bugs [Accessed: 20/07/16]
Ministry of Health (2009). Guidelines for the management of norovirus outbreaks in hospitals and elderly care institutions (Web Page). Wellington: Ministry of Health. https://www.health.govt.nz/system/files/documents/publications/guidelines-management-norovirus_0.pdf [Accessed: 20/07/16]
Kirk MD, et al. World Health Organization Estimates of the Global and Regional Disease Burden of 22 Foodborne Bacterial, Protozoal, and Viral Diseases, 2010: A Data Synthesis. PLoS Med. 2015 Dec 3;12(12):e1001921.
Kun LL, et al. A Multi-Site Study of Norovirus Molecular Epidemiology in Australia and New Zealand, 2013-2014. PLoS One. 2016; 11(4): e0145254.