Abstract
Noroviruses are the commonest cause of infectious intestinal disease, and are frequently associated with outbreaks of gastroenteritis, mainly in healthcare-associated settings, but also in outbreaks associated with contaminated food and/or water. The contamination of foods can occur during production, preparation, and/or service, or, more rarely by contamination of water supply. Contamination of water supply with norovirus is rare, and usually occurs as a consequence of leakage of sewage or as a result of leaching after heavy rainfall. Outbreaks of norovirus gastroenteritis associated with contaminated food and water can have high impact as a large number of individuals can become affected quickly over a large geographical area, with a high number of secondary cases. However, adequate capture of both epidemiological and laboratory data of norovirus outbreaks remains a major challenge, as many outbreaks fail to be identified and/ or followed up and so the incidence of norovirus-associated foodborne outbreaks is not well defined. Measures for preventing norovirus contamination are centred on good hand hygiene and environmental cleaning practices in healthcare settings, food establishments and on board cruise ships. Several guidelines for responding to outbreaks in food preparation premises are available, and there is a wide range of generic legislation for food processing and handling. There is currently no licenced vaccine or antiviral drug for prophylaxis or treatment of norovirus. However, the first trial demonstrating homologous protection against illness and infection using a norovirus VLP (virus-like particle) was reported recently. Whilst promising, the vaccine is monovalent and the evidence suggests that there is little cross-protection between norovirus strains, a multivalent vaccine is likely to be the only viable option for future vaccine development.