Acute gastroenteritis is one of the most common diseases affecting children and rotavirus is the major etiological agent worldwide. Although the role of rotavirus as a causal agent of gastroenteritis has been previously established in Thailand, little is known about the epidemiology of Norwalk-like viruses.The present study was designed to determine the epidemiology and clinical manifestation of Norwalk-like viruses in comparison with rotavirus in Thailand.One hundred and one children with watery diarrhea between November 2002 and October 2003 were recruited into the study. The clinical data and stool specimens were collected for clinical analysis and rotavirus and Norwalk-like virus detection. Rotavirus and Norwalk-like viruses were detected viral agent by RT-PCR method. Of 101 stool samples obtained, rotavirus was detected in 25/101(24.7%). Norwalk-like viruses were detected in 23/101(22.7%). Dual infections were detected in 6/101(5.9%). Rotavirus and Norwalk-like viruses peaked in the winter time. Clinical manifestations of rotavirus and Norwalk-like viruses were watery stool, nausea, vomiting, abdominal pain and fever. Norwalk-like viruses and rotavirus were the most common etiologic agents in children with acute gastroenteritis in Thailand. Epidemiology and clinical
manifestations of rotavirus and Norwalk-like viruses were not different.

Keywords: Rotavirus, Norwalk-like virus, Acute gastroenteritis