Norovirus(formerlyNorwalkvirus)isanRNAvirus(taxonomicfamilyCaliciviridae)whichcausesapproximately90%ofepidemicnon-bacterialoutbreaksofgastroenteritisaroundtheworld,andmayberesponsIBLefor50%ofallfoodborneoutbreaksofgastroenteritisintheUS.Norovirusaffectspeopleofallages.Thevirusesaretransmittedbyfaecallycontaminatedfoodorwaterandbyperson-to-personcontact.Afterinfection,immunitytonorovirusisusuallyincompleteandtemporary.Thereisaninheritedpredispositiontoinfection,andindividualswithbloodtypeOaremoreofteninfected,whilebloodtypesBandABcanconferpartialprotectionagainstsymptomaticinfection.Outbreaksofnorovirusinfectionoftenoccurinclosedorsemi-closedcommunities,suchaslong-termcarefacilities,overnightcamps,hospitals,prisons,dormitories,co-ops,andcruiseshipswheretheinfectionspreadsveryrapidlybyeitherperson-to-persontransmissionorthroughcontaminatedfood.Manynorovirusoutbreakshavebeentracedtofoodthatwashandledbyoneinfectedperson.Norovirusisrapidlyinactivatedbysufficientheatingandbychlorine-baseddisinfectants,butthevirusislesssusceptibletoalcoholsanddetergentsasitdoesnothavealipidenvelope.
