The R.E.P. has launched the project of collecting stool samples in Klongtoey, Bangkok.  Norovirus infections cause to severe diarrhea and vomiting. Transmissions occur through contact with infected individuals or through exposure to contaminated food and water or infectious aerosols. Norovirus infection is prevalent worldwide including Thailand and Japan every year. The mechanism of onset of norovirus outbreak has remained to be clarified. In collaboration with the Research Institute for Microbial Diseases (RIMD), Osaka University, we began a stool specimen collection project from healthy volunteers to investigate the asymptomatic carriers of norovirus infection at Klongtoey area in Bangkok. This project is useful to clarify that 1) how does norovirus propagate in our body, 2) how infectious noroviruses are maintained in our living environment, and 3) is there any link between norovirus outbreak and asymptomatic carriers. This project would be useful to prevent norovirus outbreaks occurring in the future.