Children born on or after April 1, 2006 presenting to CCHMC as an inpatient or for a short-stay or Emergency Department (ED) visit with acute gastroenteritis (AGE) and/or fever will be approached for enrollment. Children will be eligible if they have vomiting and/or diarrhea less than or equal to 10 days duration. Data including demographic information, illness characteristics and socio-economic status will be collected from each patient. A sample of the patient's stool will be collected within 14 days of the onset of symptoms. Stool specimens will be tested for rotavirus antigen by Rotaclone at CCHMC. All rotavirus positive stool specimens will be typed for common G and P serotypes. Using the children identified with rotavirus as our cases and the children who were rotavirus negative as our controls, we will conduct a case control study to assess the effectiveness of rotavirus vaccines, in particular Rotarix.