Norovirus is a genus of genetically diverse single-stranded RNA, non-enveloped viruses in the Caliciviridae family.

The known viruses in the genus are all considered to be the variant strains of a single species called Norwalk virus. 


The viruses are transmitted by fecally contaminated food or water; by person-to-person contact; and via aerosolization of the virus and subsequent contamination of surfaces.

Noroviruses are the most common cause of viral gastroenteritis in humans, and affect people of all ages.

Norovirus infection is characterized by nausea, forceful vomiting, watery diarrhea, and abdominal pain, and in some cases, loss of taste. General lethargy, weakness, muscle aches, headache, coughs, and low-grade fever may occur. 

The disease is usually self-limiting, and severe illness is rare. 

The virus affects around 267 million people and causes over 200,000 deaths each year; these deaths are usually in less developed countries and in the very young, elderly and immuno-suppressed.

Winter vomiting bug is a common term for noroviruses in the UK, because the virus tends to cause vomiting and to spread more easily in winter, when people tend to spend more time indoors and near to each other.

Outbreaks of norovirus infection often occur in closed or semiclosed communities, such as long-term care facilities, overnight camps, hospitals, prisons, dormitories, and cruise ships, where the infection spreads very rapidly either by person-to-person transmission or through contaminated food.

Many norovirus outbreaks have been traced to food that was handled by one infected person.

Norovirus is rapidly inactivated by either sufficient heating or by chlorine-based disinfectants, but the virus is less susceptible to alcohols and detergents, as it does not have a lipid envelope.

The genus name Norovirus is derived from Norwalk virus, the only species of the genus. The species causes approximately 90% of epidemic nonbacterial outbreaks of gastroenteritis around the world, and may be responsible for 50% of all foodborne outbreaks of gastroenteritis in the United States.
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