Foodborne Illness

Common bacteria and viruses that cause food poisoning. An informational site sponsored by Marler Clark


Norovirus is the leading cause of gastroenteritis, or what we commonly think of as stomach flu symptoms. It causes 23 million cases of gastroenteritis per year, or over half of all gastroenteritis cases in the U.S., and is the second most common virus after the common cold. 

Norovirus is usually transmitted from the feces to the mouth, either by drinking contaminated food or water or by passing from person to person. Because noroviruses are easily transmitted, are resistant to common disinfectants, and are hard to contain using normal sanitary measures, they can cause extended outbreaks.

Symptoms of Norovirus

The norovirus incubation period tends to be 24 to 48 hours, after which symptoms begin to appear. An infection normally lasts only 24 to 60 hours. However, in some cases, dehydration, malnutrition, and even death can occur. These complications are more likely among children, older people, and patients in hospitals and nursing homes with weakened immune systems. Common symptoms include:

  • Nausea
  • Diarrhea
  • Vomiting
  • Abdominal pain
  • Headache
  • Low-grade fever

Norovirus Diagnosis

Norovirus usually takes its course and goes away on its own after one to three days. It is hard to diagnose using samples in a lab, and so is usually diagnosed based on the combination of common symptoms, including mild fever, vomiting, and short duration of illness.

Norovirus Treatment

There is no specific treatment for norovirus. However, it is essential to replenish fluids and minerals, as these are depleted with diarrhea.

How to Prevent Norovirus Infection

The good news is that norovirus does not multiply on food, since it is a virus and not a bacterium. There is no way to tell whether foods – like shellfish, which are often eaten raw – are contaminated with norovirus. The only way to assure you don’t get norovirus from foods like shellfish is to cook them thoroughly. Here are other norovirus prevention methods:

  • Wash hands properly, especially after being at events with catered meals, nursing homes, schools, or on cruise ships
  • Wash raw vegetables thoroughly before serving them
  • While traveling, only drink boiled drinks or carbonated bottled beverages
  • Avoid letting anyone known to have norovirus in kitchen spaces

Additional Resources for Norovirus is a comprehensive site with in-depth information about norovirus infection.