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Public Health - Seattle & King County

Norovirus infection

Norovirus is a common cause of gastroenteritis. It is often responsible for outbreaks in schools, child care centers, long term care facilities for the elderly, and on cruise ships. More than 50 percent of all food borne illnesses in the United States are caused by norovirus, most often from ill food workers who contaminate the food they prepare. People infected with norovirus may still be contagious for at least 3 days after they are better. Norovirus infections occur year round but are more common during the winter months. The illness is sometimes incorrectly called "the stomach flu" or "the 24-hour flu" by both health care providers and lay people. In fact, norovirus and influenza (the virus that causes the flu) are unrelated viruses that typically cause different illnesses. While each virus can produce a wide range of symptoms (from none at all to severe) the table below summarizes the general differences.

What are the differences between norovirus and influenza ("the flu")?

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Norovirus Infection
Influenza ("the flu")
What are the symptoms? Often has sudden onset of nausea and vomiting and/or watery diarrhea with cramps. Low grade fever, chills, body aches sometimes occur. Often has sudden onset of fever (up to 104º F), headache, sore throat, cough, body aches and congestion. Vomiting and diarrhea are less common.
How long does it last? Typically between 24 and 72 hours Typically between 3 and 7 days, often longer
Is it serious? Rarely causes severe complications. Dehydration is the most common complication, particularly among young children and the elderly. Usually gets better on its own but can cause severe complications, especially among young children, the elderly, and people with underlying health problems (such as asthma, chronic lung disease, chronic heart disease, diabetes, etc.)
How is it prevented?
  • No vaccine is available for norovirus
  • Anyone with norovirus symptoms should wait at least 48 hours after their last episode of vomiting and/or diarrhea before preparing food for others.
  • Wash hands with soap and water after using the toilet or changing diapers, and before preparing food or eating.
  • Cook shellfish thoroughly before eating.
  • Vaccine is available but needs to be repeated each flu season.
  • Anyone with flu symptoms should stay home from work and school until at least 24 hours after the fever is gone.
  • Wash hands frequently with soap and water, or use hand sanitizer if soap and water are not available.
  • Cover coughs and sneezes with the elbow or shoulder, or with a tissue that is immediately thrown away.

Resources for the general public

Wash hands with warm water and soap

Resources for health care providers and long-term facilities

Elder patient