skip to main content

Public Health - Seattle & King County

Norovirus fact sheet

What is it?

Noroviruses are common and very contagious viruses that cause diarrhea and vomiting. Although people who have norovirus infection may feel very sick for several days, the illness is seldom serious.

What are the symptoms?

  • Symptoms often begin suddenly 12 to 48 hours after exposure to norovirus and include:
    • Nausea and vomiting
    • Watery, non-bloody diarrhea
    • Stomach cramps
    • Fever and chills
    • Headache and muscle aches
  • Most people recover fully within one to three days. Dehydration (loss of fluids) can occur and may result in hospitalization.

How is it spread?

  • Norovirus leaves the body through the stool (feces) and vomit of infected persons. It easily spreads from one person to another. People can become infected with the virus by:
    • Eating food or drinking liquids that are contaminated with norovirus. Ill food handlers may contaminate foods that are consumed undercooked or raw (including produce and shellfish).
    • Touching surfaces or objects contaminated with norovirus and then putting their hands in their mouth or sharing foods or utensils with someone who is infected.
    • Inhaling virus released when an infected person vomits.
    • Having close contact with an infected person.
  • Norovirus can cause outbreaks in childcare centers, long-term care facilities, schools, cruise ships and other group settings.
  • People infected with norovirus are most contagious from the moment they begin feeling ill until at least 3 days after symptoms end.

How is norovirus diagnosed and treated?

  • A healthcare provider usually makes the diagnosis based on a person’s symptoms.
  • Laboratory testing of stool or vomit for norovirus is sometimes done during outbreaks.
  • Treatment consists of drinking plenty of fluids and adequate rest. Antibiotics are not effective against norovirus.

How can norovirus infection be prevented?

  • Wash your hands carefully with soap and warm water after using the bathroom, changing diapers, before eating, and before preparing food.
  • Wash fruits and vegetables thoroughly before eating and avoid eating undercooked oysters or other shellfish.
  • Promptly clean and disinfect toilets, sinks, and other areas that may be contaminated with vomit or stool (i.e. countertops, floors).
  • After cleaning, wash the area with soap and water, then disinfect with a solution of 1/3 cup household bleach mixed with one gallon of water. Leave on the surface for 10 minutes, rinse with water, then air dry. Carpets can be disinfected by steam cleaning. See complete list of EPA approved disinfectants against norovirus (PDF).
  • Promptly remove and wash clothing or linens if they become soiled with stool or vomit. Use hot water and soap to launder.
  • Avoid preparing food for others for at least 2 to 3 days after symptoms have ended.

For the general public:

For King County health care providers: