Norovirus has high genome variability that results in a large number of genetic variants.  At present, norovirus is divided in five genogroups (GG I to V); a minimum of 20 genotypes are differentiated within genogroups I and II. Norovirus is found worldwide, with humans being the only known reservoir of the pathogen.

Outbreak Measures

Should an outbreak occur, it is important to identify the source of the infection rapidly. Should contaminated food or drinks be possible causes, action to eliminate this source must be taken immediately.

Control measures should be carried out immediately, even before the laboratory has issued a final diagnosis confirmation, if there are indications of a norovirus outbreak. Comprehensive hygiene measures (the wearing of protective gloves and gowns, quarantining of infected individuals, additional cleaning of toilets, intensive hand hygiene, repeated disinfection of bedclothes) are necessary to avoid faecal-oral transmission. However, the effect of such action is limited due to the highly contagious nature of norovirus. It has been regularly observed that further infections cannot be completely prevented despite thorough hygiene measures.

The movement of patients, residents and staff members in community facilities, such as hospitals and retirement homes, should be limited to minimise the spread of infections across departments and stations of such institutions. Infected staff members should be sent on sick leave, even if they only show mild symptoms of gastrointestinal health problems and return to work only after a minimum of two days following the ceasing of clinical symptoms and adhering strictly to hand hygiene guidelines.