Norovirus infection can cause severe vomiting and diarrhea that start suddenly. Noroviruses are highly contagious. They commonly spread through food or water that is contaminated during preparation or through contaminated surfaces. Noroviruses can also spread through close contact with a person who has norovirus infection.Diarrhea, stomach pain and vomiting typically begin 12 to 48 hours after exposure. Norovirus infection symptoms usually last 1 to 3 days. Most people recover completely without treatment. However, for some people - especially young children, older adults and people with other medical conditions - vomiting and diarrhea can be severely dehydrating and require medical attention.Norovirus infection occurs most frequently in closed and crowded environments. Examples include hospitals, nursing homes, child care centers, schools and cruise ships.