Norwalk Virus / Noroviruses are a group of related, single-stranded RNA, nonenveloped viruses that cause acute gastroenteritis in humans.
Noroviruses are named after the original strain ‘Norwalk virus’, which caused an outbreak of gastroenteritis in a school in Norwalk, Ohio, in 1968. No evidence suggests that infection occurs through the respiratory system. Noroviruses are highly contagious and as few as 10 viral particles may be sufficient to infect an individual. During outbreaks of norovirus, several modes of transmission have been documented; for example, initial food-borne transmission in a restaurant, followed by secondary person-to-person transmission to household contacts. 50% of all food-borne outbreaks of gastroenteritis can be attributed to Noroviruses. Among the 232 outbreaks of Norwalk Virus Norovirus illness reported to CDC from 1997 to 2000 36% were in restaurants, 23% were in nursing homes, 13% were in schools and 10% were vacation settings or cruise ships.