Shellfish and salad ingredients are the foods most often implicated in Norwalk outbreaks. Ingestion of raw or insufficiently steamed clams and oysters poses a high risk for infection with Norwalk virus. Foods other than shellfish are contaminated by ill food handlers. Norwalk virus infection symptoms include nausea, vomiting, diarrhea and abdominal cramps. Symptoms experienced less often include headache, fever, chills and muscle pain.
Fluid replacement is the common therapy.
Over three million cases of rotavirus gastroenteritis occur annually in the United States, primarily in the winter. All age groups are susceptible to rotavirus infection, but children six months to 2 years of age, premature infants, the elderly, and the immune-compromised are particularly prone to more severe symptoms. Outbreaks of rotavirus diarrhea are common among hospitalized infants, young children attending day care centers and elderly persons in nursing homes. The incubation period ranges from one to three days. Symptoms often start with vomiting followed by four to eight days of diarrhea.