Viral gastroenteritis can be caused by several viruses. Norovirus is the leading cause of acute diarrhea for adults, whereas rotovirus is the leading cause of gastroenteritis for the pediatric population, especially for children up to 2 years of age. However, the incidence of rotovirus in children has fallen significantly since the introduction of the rotovirus vaccine. It is possible for adults to have a rotovirus infection, but generally it is less common and clinically milder in presentation. Other rarer viral etiologies include CMV and HSV and they tend to occur more often in immunocompromised patients.