 This study will be performed at six large hospitals in Lebanon in the three largest cities Beirut, Tripoli, and Saida. The study will enroll children younger than 5 years of age who are admitted to the hospital because of gastroenteritis. Enrollment will continue for a period of two years at each hospital. Inclusion criteria are age 5 years, with gastroenteritis as the main reason for admission to the hospital or for a stay in the Emergency Department longer than 12 hours. Exclusion criteria include onset of symptoms beyond 12 hours of admission health-care associated infection. For all enrolled subjects, data will be collected about severity of illness, outcome, and history of vaccination. Stool samples will be collected for genotyping of rotavirus. 