Norovirus (Norwalk Virus)

Norwalk virus infection is an intestinal illness that often occurs in outbreaks. Also known as the ‘winter vomiting bug’

 Noroviruses are a group of single-stranded RNA viruses in the family Caliciviridae that cause acute gastroenteritis in humans. Norwalk virus is the prototypical strain in the genus. Norovirus infection is an important cause of acute gastroenteritis in humans and is the most frequently implicated cause of outbreaks of viral gastroenteritis worldwide. Noroviruses cause an estimated 20% of all viral gastroenteritis cases in persons older than 24 months. Norwalk virus was first associated with gastroenteritis in 1972.

It was identified by electron microscopy of stool samples that had been saved from a 1968 gastroenteritis epidemic that occurred in Norwalk, Ohio. In a 2-day period, acute gastroenteritis developed in 50% of 232 students or teachers in an elementary school. The virus initially was labeled as a small, round, structured virus, and it was named after the city in which the outbreak occurred. Recently, norovirus infections have made news as the cause of several outbreaks of gastroenteritis on cruise ships.