Noroviruses are a group of viruses that cause the "stomach flu," or gastroenteritis.

Viruses are very different from bacteria and parasites, some of which can cause illnesses similar to norovirus infection.

Like all viral infections, noroviruses are not affected by treatment with antibiotics, and cannot multiply outside of a person's body.



Symptoms usually begin about 24 to 48 hours after ingestion of the virus, but they can appear as early as 12 hours after exposure.

Symptoms usually include:

  • nausea
  • vomiting
  • diarrhea
  • some stomach cramping

In addition, people sometimes have:

  • a low-grade fever
  • chills
  • headache
  • muscle aches
  • a general sense of tiredness

The illness often begins suddenly, and the infected person may feel very sick. In most people the symptoms last about 1 or 2 days and resolve without treatment.

Noroviruses are found in the stool or vomit of infected people.

Individuals can become infected with the virus in several ways, including:

  • Eating food or drinking liquids that are contaminated with norovirus;
  • Touching surfaces or objects contaminated with norovirus, and then placing their hands in their mouth;
  • Having direct contact with another person who is infected and showing symptoms (for example, when caring for someone with illness, or sharing foods or eating utensils with someone who is ill).

Noroviruses are very contagious and can spread easily from person to person. Both stool and vomit are infectious.

Particular care should be taken when dealing with young children in diapers who may have diarrhea.

People infected with norovirus are contagious from the moment they begin feeling ill to at least 3 days after recovery. The virus "sheds" for 72 hours after the last symptoms. Therefore, it is particularly important for people to use good handwashing and other hygienic practices after they have recently recovered from a norovirus illness.

Currently, there is no antiviral medication that works against norovirus and there is no vaccine to prevent infection. Norovirus infection cannot be treated with antibiotics because antibiotics are not effective against viruses.

If you are ill with vomiting and diarrhea, stay home and stay hydrated with plenty of fluids.

Dehydration is the most serious health effect that can result from norovirus infection. By drinking oral rehydration fluids (ORF), juice, or water, you can reduce your chance of becoming dehydrated. Sports drinks are an effective supplement for rehydration but should not be used alone since they are low in sodium and potassium.

If you can't keep down any fluids and are feeling very thirsty or lightheaded, please see your health care provider.

You can decrease your chance of contracting or spreading norovirus by following these preventive steps:

  • Stay home when you are feeling ill.
  • If you work in food service, day care or other health care facilities, stay away from work for 72 hours after your last symptoms.
  • It is best to stay away from group situations for 72 hours after your last symptoms. If you must attend class or other group gatherings, use scrupulous handwashing with soap and water and limit direct contact with others.
  • Frequently wash your hands, especially after using the toilet or changing diapers and before eating or preparing food. Do not prepare food for others while you have symptoms and for 72 hours after.
  • Handwashing with soap and water is highly recommended. There is evidence that waterless alcohol-based hand cleansers may not provide full skin disinfection against noroviruses.
  • Thoroughly wash fruits and vegetables, steam oysters before eating them and cook foods well. (Transmission can occur through eating contaminated foods).
  • Norovirus is a very robust and durable virus that is highly transmissible and can live for extended periods on environmental surfaces. Disinfect potentially contaminated surfaces thoroughly with diluted bleach: one part bleach to 9 parts water (1/3 cup bleach to 1 gallon of water.)
  • Immediately remove and wash clothing or linens that may be contaminated with virus after an episode of illness (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.

Source: Centers for Disease Control and Prevention