Norovirus Infection

(Acute Nonbacterial Gastroenteritis; Caliciviruses; Food Infection; Norwalk Virus; Norwalk-like Virus; Small Round Structure Viruses [SMRVs]; Stomach Flu; Viral Gastroenteritis)


Norovirus infection happens in the stomach and intestines. The stomach flu is another name for it. It spreads quickly.

The Digestive Tract

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Causes    TOP

A group of viruses cause this infection. They can spread through:

  • Water that is not clean, such as lakes, swimming pools, wells, and water stored on cruise ships
  • Raw or poorly steamed shellfish, such as clams and oysters
  • Food and drinks made by food handlers with the infection who do not wash their hands well after using the bathroom
  • Surfaces, such as a door knob

The viruses can also spread by being around someone who is sick.

Risk Factors    TOP

Any person who ingests the virus is at risk of getting this infection. It is more common in young children and older adults.

This infection is common in crowded settings such as:

  • Cruise ships
  • Restaurants
  • Nursing homes
  • Hospitals
  • Child care centers
  • Hotels

Symptoms    TOP

You may have:

These signs often appear within 24-48 hours of getting the virus. They often last about 2-3 days.

Diagnosis    TOP

You will be asked about your symptoms and health history. You will have a physical exam. Often, this is enough to tell if you have the infection.

You don’t need to find out which virus is causing your infection. Stool tests may be done if your doctor wants to find this out.

Treatment    TOP

A norovirus infection will go away on its own. The infection is often brief and mild.

Most people will get better by resting and drinking plenty of fluids. Oral rehydration solutions can help. These can be found in most drugstores. Rarely, you may need IV fluids if you have severe dehydration.

Antibiotics are not helpful against viruses. There are no antiviral medicines or vaccines used to fight or prevent this infection.

Prevention    TOP

To help lower your chance of getting noroviruses:

  • Wash your hands well with soap and water:
    • After using the bathroom
    • After changing diapers
    • Before you make or eat food.
  • If you are caring for someone who is infected, make sure the person washes his or her hands very well.
  • If you are ill or caring for someone who is ill, clean contaminated surfaces right away using bleach cleaner. Remove and wash soiled linens. Use hot water and soap.
  • Wash fruits and vegetables.
  • Cook oysters and clams before eating them.
  • Throw away contaminated food.


Centers for Disease Control and Prevention
National Institute of Allergies and Infectious Diseases


Public Health Agency of Canada


Norovirus. Centers for Disease Control and Prevention website. Available at:
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Updated July 16, 2018. Accessed July 18, 2018.
Norovirus infection. EBSCO DynaMed Plus website. Available at: . Updated July 31, 2017. Accessed July 18, 2018.
Norovirus illness: Key facts: Centers for Disease Control and Prevention website. Available at:
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Published January 2015. Accessed July 18, 2018.
Phillips G, Tam CC, Rodrigues LC, Lopman B. Risk factors for symptomatic and asymptomatic norovirus infection in the community. Epidemiol Infect. 2010 Dec 17:1-11.
Scallan E, Hoekstra RM, et al. Foodborne illness acquired in the United States-major pathogens. Emerg Infect Dis. 2011;17(1):7-15.
Last reviewed May 2018 by James Cornell, MD
Last Updated: 7/18/18

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