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Norovirus (cont.)

What Is the Cause of a Norovirus Infection?

Norovirus is transmitted from person to person. Ingestion of food or contact with other material contaminated with fluid or feces from a person infected with norovirus causes norovirus infection.

After an individual has contracted norovirus, it first attaches to cells in the gastrointestinal tract. The virus enters the cells, triggering the gastrointestinal tract to cause vomiting and preventing good fluid adsorption, which results in diarrhea. Because the virus is very difficult to cultivate in the laboratory, it has not been precisely determined exactly how the virus causes disease. The norovirus has been referred to by many names (for example, Norwalk virus, Norwalk-like virus or NLV, SRSV [small round structured viruses], and Snow Mountain virus). Many of these names often arise from the area or region where an outbreak occurs, like Toronto virus, Hawaii virus, or Bristol virus. Common names like "winter vomiting virus" or "stomach flu" are also used. "Stomach flu" is not related to any type of influenza; the term was likely coined because of the frequent watery diarrhea norovirus produces which is like the frequent clear or "watery" nasal discharge of the flu.

Is Norovirus Contagious?

Norovirus is highly contagious from person to person. It is mainly spread by the fecal-oral route from person to person, either directly by contact with an infected individual or indirectly by contaminated foods or surfaces. The virus is also spread by droplets in the air (usually by droplets associated with vomiting), and if the droplets land on food or other objects, the virus can be transmitted to the mouth when touched by the hands.

Contaminated food is a common means of spread. Contamination of food occurs when people who are infected handle or prepare food under improper hygienic conditions. Foods that become contaminated with norovirus and are commonly involved in outbreaks of norovirus illness include

  • leafy greens,
  • fresh fruits,
  • shellfish.

Researchers have shown that human noroviruses can be carried by other animals such as dogs, which can transmit the viruses to humans. Consequently, some investigators consider norovirus infections to be a zoonotic disease (a disease transferred between animals and humans).

Medically Reviewed by a Doctor on 1/7/2016

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