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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. It spreads quickly to others.


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 who have the infection and 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

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


Problems may be:

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


The doctor will ask about your symptoms and health history. A physical exam will be done. This is often enough to make the diagnosis.

Stool tests may be done if the doctor wants to find out which virus is causing the infection.


Viral infections cannot be treated with antibiotics. The infection will go away on its own. Symptoms can be managed with:

  • Supportive care, such as drinking plenty of fluids
  • Medicines to ease pain, such as acetaminophen


To lower the risk of this problem:

  • Practice proper hand washing.
  • Handle and prepare food safely.
  • Avoid people who are sick.
  • Clean and disinfect surfaces.

Centers for Disease Control and Prevention

National Institute of Allergies and Infectious Diseases


Health Canada

Public Health Agency of Canada


Bok K, Green KY. Norovirus gastroenteritis in immunocompromised patients. N Engl J Med. 2012 Nov 29;367(22):2126-2132.

Norovirus. Centers for Disease Control and Prevention website. Available at: http://www.cdc.gov/norovirus/about/overview.html. Accessed October 30, 2020.

Norovirus infection. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/norovirus-infection. Accessed October 30, 2020.

Last reviewed September 2020 by EBSCO Medical Review Board James P. Cornell, MD