Norwalk Virus Infection (calicivirus)

Last Reviewed: November 2006

What is Norwalk virus infection?

Norwalk virus infection is a gastrointestinal illness that occurs sporadically or in outbreaks. The virus was first identified during a gastroenteritis outbreak in Norwalk, Ohio, in 1972. There are a number of strains of Norwalk virus which are also referred to as calicivirus.

Who gets Norwalk virus infection?

Anyone can become infected. It only occurs in humans and is found worldwide.

How is it spread?

Norwalk viruses are spread by exposure to infected people or contaminated food and water. The virus is passed in stool and vomit. Outbreaks have been linked to sick food handlers, contaminated shellfish or water contaminated with sewage. It is generally spread from person to person by direct contact, but some medical reports suggest that the virus can spread through the air during vomiting.

What are the symptoms?

Although the virus is easy to spread, serious illness rarely occurs. The most common symptoms include nausea, vomiting, and stomach cramps. Diarrhea may occasionally accompany vomiting. Fever is usually low grade or absent. Infected people generally recover in one to two days.

How soon after exposure do symptoms appear?

The incubation period is one to two days.

What is the treatment for Norwalk virus infection?

No specific treatment is available. Persons who become dehydrated might need to be rehydrated by taking liquids by mouth. Occasionally patients may need to be hospitalized to receive intravenous fluids.

How can Norwalk virus infection be prevented?

The following recommendations may reduce the risk of acquiring or spreading the infection:

  • wash hands thoroughly after each toilet visit and before preparing food.
  • people who experience nausea, vomiting or diarrhea should not attend school or work and should not handle food for others while ill.
  • avoid drinking untreated water.
  • cook shellfish thoroughly before eating.