Rotaviruses comprise a genus within the family Reoviridae and are responsible for significant gastrointestinal disease, primarily in children <5 years of age and the young of other mammalian species. The rotavirus genus is divided into serological groups (A – E). Groups A to C infect humans, and all groups infect animals. Rotavirus A infection alters the function of the small intestinal epithelium, resulting in diarrhea. Some rotavirus infections are asymptomatic, which suggests that both viral and host factors can affect disease severity.