Abstract
Wild oysters and clams were collected at an estuary receiving treated municipal wastewater in Sendai city from two municipal wastewater treatment plants between October 2017 and February 2018 and then examined for Norovirus in their digestive tissues. Norovirus was detected from both oysters (2.2log copies/ g-DT) and clams (2.5log copies/ g-DT) even before the epidemic of gastroenteritis. The concentration of Norovirus GII in the samples obviously increased during the epidemic, while such an increase was not found for Norovirus GI. The concentration of Norovirus GII in the shellfish samples was significantly correlated with the number of gastroenteritis patients reported in the city. This result indicates that reduction of gastroenteritis patients in the city can contribute to improved safety of shellfishes harvested at the downstream.
