Norovirus (was "Norwalk-like viruses"), an RNA virus of the Caliciviriae taxonomic family, causes approximately 90% of epidemic non-bacterial outbreaks of gastroenteritis around the world, and is responsible for 50% of all foodborne outbreaks of gastroenteritis in the US. Norovirus affects people of all ages. The viruses are transmitted by faecally contaminated food or water and by person-to-person contact.