Norwalk virus infection is caused by the Norwalk virus. The virus was first identified in 1972 after an outbreak of gastrointestinal illness in Norwalk, Ohio. Later, other viruses with similar features were described and called Norwalk-like viruses. These have since been classified as members of the calicivirus family. Norwalk and Norwalk-like viruses are found worldwide.
Humans are the only known hosts.
The viruses are passed in the stool of infected persons. People get Norwalk virus infection by swallowing food or water that has been contaminated with stool from an infected person. Outbreaks in the United States are often linked to eating raw shellfish, especially oysters and clams. Anyone can get Norwalk virus infection, but it may be more common in adults and older children. Nausea Vomiting Diarrhea Stomach cramps Severe illness or hospitalization is uncommon.