Rotavirus is the most common cause of severe, dehydrating diarrhea among children worldwide. Scientists have described seven rotavirus groups (A to G). Only groups A, B, and C infect humans. Group A, which has multiple strains, causes the majority of childhood infections. Although human of all ages are susceptible to rotavirus infection, children 3 to 24 months of age account for the vast majority of severe infections. A person with rotavirus diarrhea often excretes large amounts of virus, which can spread readily through contaminated hands. Rotavirus, a hearty virus that survives easily in the environment, can also be transmitted through contaminated objects, water or food.