Floods are not only the dangerous disaster situation threatening human lives, but they also can pose additional risks for human health. Less attention has been paid to indirect health impacts of floods such as health problems than direct impacts (e.g. loss of life, destructions of property and agricultural crops). This is due to difficultly to prove the damage to human health via indirect routes such as contaminated water and food, although floods are likely to impact on human health physically

more »

... and psychologically. In terms of physical health impacts, floods are potentially able to cause gastroenteritis diseases outbreaks. While norovirus (NoVs) is well known as a leading causal pathogen for acute gastroenteritis in developed countries, structured data on the prevalence of the disease in developing countries are not available thus far. Oysters are often associated with NoV infection due to its feature to accumulate the virus from surrounding water environment. If oysters are contaminated by NoVs transported from urban area by floodwater, urban flood potentially increases the risk of foodborne diseases by consuming oysters. On the other hand, based on the above feature, NoV contamination in oysters was reported to be well correlated to number of cases of gastroenteritis in some developed countries. In terms of psychological impact, in some areas of developing countries hit by flooding frequently, people seem to adapt their lives to the floodwater so well. As an indicator of the psychological impact, people's feeling to a disease is important in the estimation of its burden but this relationship has not been investigated especially for common diseases with a low fatality. Hue City, located in central of Vietnam, is known as a flood city. About twothirds of the city's residents are likely exposed to flooding when a heavy rainy occurs. Since the city has no wastewater treatment plant, domestic wastewater is discharged directly into drainage channels, although a part of wastewater passes through septic tanks. The channels flow directly into the Perfume River. Oysters cultivated in the downstream of the river are probably affected by contaminants from the city where urban flooding occurs regularly. This area has potential to show indirect impacts of flood as above described and so it was selected for the field of this study. The present study aims (1) to estimate the prevalence of NoVs in cases of acute gastroenteritis in