Environmental Health and Safety

Norovirus Fact Sheet

an electron micrograph of the Norovirus, CDC image ID 2172

What is norovirus?

Noroviruses are a group of viruses (previously known as Norwalk-like viruses) that can cause gastroenteritis, an inflammation of the stomach and intestines. Norovirus is the leading cause of foodborne illness outbreaks in the United States.

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.

What are the 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. The infected person may feel very sick and vomit often, sometimes without warning, many times a day. Sometimes people infected with norovirus have no symptoms at all, but can still pass the illness to others.

How long does it last?

Most people recover in 1 or 2 days and have no long-term adverse health effects. Sometimes, infected people may experience milder symptoms for a week or more.

How is it spread?

Noroviruses are found in the stool (feces) or vomit of infected people. From there, noroviruses are transferred to food, water, or surfaces by the hands of infected people who have not washed adequately after using the bathroom.

People become infected with norovirus by:

  • Eating food or drinking liquids contaminated by an infected person.
  • Eating uncooked shellfish that has been harvested from contaminated waters.
  • Touching contaminated surfaces or objects and then touching their mouth or eating without washing their hands first.

What should I do if I have symptoms?

  • Drink plenty of fluids so you don’t become dehydrated.
  • Wash your hands often.
  • Contact your health care provider (but remember that antibiotics don’t treat viruses).

How can I prevent norovirus infections?

  • Wash your hands often!
    • After using the bathroom
    • After changing diapers
    • Before preparing foods
    • Before eating
  • Wash your hands more often when someone in your household is sick.
  • Clean and disinfect surfaces with household bleach immediately after vomiting or diarrheal accidents.
  • Wash and/or peel fruits and vegetables before eating them.
  • Steam oysters before eating them.
  • See any current food safety alert for more information.

To report a suspected foodborne illness, call EHS at 512-471-3511