Viral diseases: infections of the gastrointestinal tract.

In the 1970s investigations generated a remarkable amount of information on the viruses responsible for acute gastroenteritis. The two viruses responsible for most cases occur in epidemiologically distinct clinical forms. Although occasionally epidemic, rotavirus infections are usually sporadic and primarily affect infants and young children. This illness is characterized by severe diarrhea commonly lasting five to eight days and frequently associated with upper respiratory tract symptoms, fever, and vomiting. The Norwalk agent and Norwalk-like viruses are characteristically epidemic and responsible for community-wide outbreaks of gastroenteritis among all ages. The disease this agent produces usually lasts 24 to 48 hours and is characterized by various combinations of vomiting, diarrhea, nausea, headache, and low-grade fever.