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University of Minnesota Extension


What is Norovirus?

Noroviruses are a group of viruses (previously known as Norwalk virus) that can cause gastroenteritis, an inflammation of the stomach and intestines. Norovirus is the leading cause of foodborne illness outbreaks in Minnesota. This infection is often mistakenly referred to as the “stomach flu” – it is not related to the flu (influenza), which is a common respiratory illness caused by the influenza virus.

Norovirus symptoms

Common symptoms of norovirus infection include vomiting, diarrhea and stomach cramping. Less common symptoms can include low-grade fever or chills, headache and muscle aches. Symptoms usually begin 1 or 2 days after ingesting the virus, but may appear as early as 12 hours after exposure. The illness often comes on suddenly.

Do not work with food while experiencing symptoms

Noroviruses are found in the stool (feces) or vomit of infected people. People can become ill from a remarkably small amount of these viruses. And remember, you won’t see norovirus – it’s microscopic. Research shows that it only takes 10 to 100 norovirus viral particles to make someone ill. By comparison, one gram of feces can contain up to 10,000,000 viral particles and one projectile vomiting incident can potentially contaminate the environment with 30,000,000 viral particles. The virus can be spread by foodborne, airborne, person-to-person and environment-to-person transmission.

So, people working with food who are sick with norovirus gastroenteritis are a high risk to others because they touch food contact surfaces and handle the food and drink other people will consume. Since the virus is so small, a sick food handler can easily – without meaning to – contaminate the food he or she is handling.

Keys to prevention

The keys to preventing the spread of norovirus include proper handwashing and not working while ill.

Remind your workers they:

  • Cannot work if they have vomiting and/or diarrhea.
  • Need to tell you if they have these symptoms.
  • MUST properly wash their hands!

Every food handler on every shift must be trained in proper handwashing and illness reporting procedures. See more details on handwashing from MDH.

Train all employees to report symptoms of vomiting and diarrhea and to stay away from work. Use your employee illness log to document all cases of vomiting and diarrhea.

As a certified food protection manager, help your employees understand and follow proper handwashing and illness reporting policies. Make a positive difference by setting a good example.

Kathy Brandt, Extension educator and Suzanne Driessen, Extension educator

Reviewed in 2021

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