<qa>  What is the main reason for admission to the hospital?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. 