Viral pathogens can infect the gastrointestinal tract in both children and adults. The syndrome typically includes diarrhea and may include other symptoms such as vomiting and abdominal pain.

Many viruses cause this syndrome, including noroviruses, rotaviruses, sapoviruses, adenoviruses, and astroviruses.

Adult patients typically present with acute onset (often within 24-48 hours of exposure) of diarrhea and vomiting. There is often associated nausea, fever, malaise, anorexia, and abdominal pain. The illness typically lasts about 2 days. Secondary attack rates can be high (especially if infection is due to the noroviruses).

Newborn infants may present with watery diarrhea and poor feeding. Fever and vomiting are less common. Some cases can be associated with electrolyte abnormalities. The illness may last up to 15 days. The severity of symptoms can vary and depend on the availability of adequate supportive care (some series report a high mortality). Although some viral pathogens have been associated with newborn nursery outbreaks, certain Escherichia coli strains are more commonly responsible.

Patients with AIDS or who are otherwise immunosuppressed may have a prolonged course associated with significant weight loss when infected with certain viral pathogens. One particular viral pathogen of importance in this population is cytomegalovirus. The differential diagnosis of diarrhea in immunosuppressed patients is quite broad, and it is helpful to involve an infectious diseases expert in the care of these patients.

Outbreaks of gastroenteritis are common in closed communities including schools, hospitals, cruise ships, and nursing homes as well as in restaurants or from catered meals.

For causes of bacterial gastroenteritis, see Gastroenteritis.