Climate change and climate variability potentially impact norovirus by influencing its transmission and prevalence; however, very few empirical and experimental observations exist to prove the effect. Norovirus-associated gastroenteritis cases are more reported in winter, but it is too early to conclude that norovirus occurs preferentially in winter and is associated with temperature, because most studies have been conducted in temperate zones, and little conclusive evidence exists on the seasonality of norovirus incidence in the tropical regions. Considering the lack of long-term data on norovirus variations in the environment, as well as various climate variables, it is important to characterise the possible influence of climate factors on norovirus occurrence in both temperate and tropical countries.

Japan, Cambodia, Viet Nam and China will collaborate in this project. Norovirus concentrations in environmental water and shellfish will be analyzed by RT-qPCR technique continuously for one year in 2-week scale, along with water quality-related climate variables. Multiple regression analysis of all combinations of predictor variables will be used, and the most significant factors will be determined. This project represents a key initial step towards understanding the effect of climate change factors on norovirus incidence and seasonality. Applications include early warning systems, environmental education, policy making, and improvement of water environment and food safety.