Norovirus is one of a family of viruses that causes stomach flu. Noroviruses are members of the 'Norwalk-like' virus group which affect the stomach and the small and large intestines. These become inflamed, causing what can be called gastroenteritis or stomach flu.
Norovirus is a non-bacterial gastroenteritis but because there are so many strains of this virus, it is unlikely that a person can develop a long-lasting immunity. Diagnosis is made by detecting the presence of Norovirus in samples of stool, vomit or food. View more information about noroviruses on the CDC website.
Norovirus is highly contagious and is found in the stool and vomit of infected people. Outbreaks have occurred in day care centers, nursing homes and at summer camps, as well as on cruise ships and restaurants. People become infected by eating food or drinking liquids that are contaminated with Norovirus, or by touching contaminated surfaces.
Direct contact with an infected person, or sharing utensils and foods, can also result in transmission. People infected with Norovirus are contagious from the moment they begin feeling ill to at least three days after the recovery. There is no evidence that people become carriers of the illness.
Although not a serious illness, during the acute stage of the infection, some people are unable to drink enough liquids to replace that lost through the vomiting and diarrhea, and therefore become dehydrated and require extra medical care. This may especially be a problem for the elderly and the very young and people with a weakened immune system.