Produced by the National Institute of Allergy and Infectious Diseases (NIAID), this photomicrograph of a fluorescent-stained cell reveals numbers of internalized green-glowing vacuoles containing numerous rotovirus particles undergoing replications. Note that the cell nucleus stained blue. Rotavirus is a contagious virus that can cause gastroenteritis (inflammation of the stomach and intestines). Symptoms include severe watery diarrhea, often with vomiting, fever, and abdominal pain. Infants and young children are most likely to get rotavirus disease. They can become severely dehydrated and need to be hospitalized and can even die.