Noroviruses are a group of viruses that cause gastroenteritis. Viruses are very different from bacteria and parasites, some of which can cause illnesses similar to norovirus infection. Viruses are much smaller, are not affected by antibiotic treatment, and cannot grow outside of a host (animal or human).
You may hear norovirus illness called “food poisoning” or “stomach flu.” It is true that food poisoning can be caused by noroviruses. But, other germs and chemicals can also cause food poisoning. Norovirus illness is not related to the flu, which is a respiratory illness caused by influenza virus.
Symptoms of norovirus illness usually begin about 24 to 48 hours after exposure to the virus, but they can appear as early as 12 hours after exposure.
The symptoms of norovirus illness usually include nausea, vomiting, diarrhea, and stomach cramps. Some people may have a mild fever, chills, headache, muscle aches, and a general sense of tiredness. The illness often begins suddenly, and the infected person may feel very sick. The illness is usually short, with symptoms lasting only about 1 or 2 days.
Noroviruses are found in the stool or vomit of an infected person. People can become infected with norovirus by eating or drinking contaminated food or water or by touching objects or surfaces contaminated with norovirus, and then placing the hand or object in the mouth.
Due to the highly infectious nature of the virus, outbreaks of norovirus are possible, particularly in settings such as long term care facilities, schools, and cruise ships. Norovirus can also be found in shellfish, especially oysters and clams, or on produce that has been washed or irrigated with contaminated water.
Your doctor can order tests to detect norovirus in stool. The tests are most accurate when performed within 2–3 days after onset of symptoms.
There is no medicine that works against norovirus and there is no vaccine to prevent infection. Severe diarrhea and/or vomiting over a long time may cause the body to lose fluid too quickly. Lost fluids should be replaced by drinking liquids such as fruit juices, soups, and special fluids called oral rehydration salts.
There is no lasting immunity. There are many different types of norovirus, and being infected with one will not protect you from getting another. Any time you are infected with a different type of norovirus, you could become ill again.
Norovirus is a common cause of gastrointestinal illness year-round, though it is more common during the winter months. While people of all ages are susceptible to infection, rates of infection in children under 5 are higher, and elderly people may be at risk for more severe illness.
- Students with diarrhea should stay home from school until the diarrhea stops. Food handlers, day care workers and health care workers should not return to work until they have their doctor’s permission
- Wash your hands well after using the toilet, changing diapers and before preparing or eating food. After changing diapers, wash the child’s hands as well as your own.
- Carefully wash fruits and vegetables, and cook seafood thoroughly.
- Immediately clean and disinfect surfaces contaminated with stool or vomit by using bleach-based household cleaner.
- Immediately remove and wash soiled clothing or linens that may be contaminated with virus (use hot water and soap).
- Flush or discard any vomitus and/or stool in the toilet and make sure that the surrounding area is kept clean.
Norovirus is a ROUTINE/ENTERIC (enteric prevention priority) notifiable condition and must be reported by phone if the individual is a food handler, direct care provider, or pre-school aged child. Otherwise routine reports may be used. Laboratory confirmed cases and suspected outbreaks should be reported.
Disease Reporting Phone Numbers (24/7)
Oahu (Disease Investigation Branch): (808) 586-4586
Maui District Health Office: (808) 984-8213
Kauai District Health Office: (808) 241-3563
Big Island District Health Office (Hilo): (808) 933-0912
Big Island District Health Office (Kona): (808) 322-4877
After hours on Oahu: (808) 600-3625
After hours on neighbor islands: (800) 360-2575 (toll free)
For more information: Centers for Disease Control and Prevention (CDC)
Last Reviewed: June 2019