Norovirus Infection

What are noroviruses?

Noroviruses are a group of viruses that cause gastroenteritis (GAS-tro-en-ter-I-tis) in people. Gastroenteritis is an inflammation of the lining of the stomach and intestines. The term norovirus is the official name for this group of viruses; however, several other names were used previously for noroviruses:

  • Norwalk-like viruses (NLVs),


  • caliciviruses (because they belong to the virus family Caliciviridae), and


  • small round structured viruses.

Viruses are very different from bacteria and parasites, some of which can cause illnesses similar to norovirus infection. Like all viral infections, noroviruses are not affected by treatment with antibiotics and cannot grow outside of a person's body.

What are the symptoms of illness caused by noroviruses?

The symptoms of norovirus illness usually include nausea, vomiting, diarrhea, and some stomach cramping. Sometimes people also have a low-grade fever, chills, headache, muscle aches, and a general sense of tiredness. The illness often begins suddenly, and the infected person may feel very sick. In most people the illness is self-limiting, with symptoms lasting for about 1 or 2 days. In general, diarrhea is more common in children and vomiting is more common in adults.

What is the name of the illness caused by noroviruses?

Illness caused by norovirus infection has several names:

  • stomach flu—this "stomach flu" is not related to the flu (or influenza), which is a respiratory illness caused by influenza virus;


  • viral gastroenteritis -- the most common name for illness caused by norovirus. Gastroenteritis refers to an inflammation of the stomach and intestines;


  • acute gastroenteritis;


  • non-bacterial gastroenteritis;


  • food poisoning (although there are other causes of food poisoning); and


  • calicivirus infection.


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