Rotavirus is a leading cause of severe winter diarrhea in infants and young children. Each year, rotavirus (RV) causes an estimated 500,000 doctor visits and 50,000 hospital admissions in the United States. Almost every child contracts RV before entering school but, with rehydration and good nutrition, nearly all fully recover. However, in poor countries RV is estimated to be responsible for at least 600,000 deaths of children under 5 years of age from RV diarrhea and dehydration each year. Aside from causing acute infantile gastroenteritis and diarrhea in young children, RV infection is typically accompanied by low-grade fever.