Infection usually causes a mild, short lived illness (which usually lasts 12-60 hours) characterised by sudden onset nausea followed by projectile vomiting and diarrhoea. Dehydration may occur and hospital treatment is sometimes necessary, particularly for those at the extremes of age.
Norovirus is highly infectious, and person-to-person spread accounts for a high proportion of cases, with outbreaks common in semi-closed settings including carehomes, schools, nurseries, hotels and cruise ships. However norovirus infection can also occur through contact with contaminated environments; eating food which has been grown in or treated with contaminated water (e.g. shellfish or fresh produce); or by infected food handlers. The true contribution made by food to the rates of norovirus infection in Scotland is currently unknown, and FSA is funding a large programme of research to improve understanding in this area.