Fate of Human Noroviruses in Shellfish and Water Impacted by Frequent Sewage Pollution Events.

Knowledge of the fate of human noroviruses (NoV) in the marine environment is key to better controlling shellfish-related NoV gastroenteritis. We quantified NoV and Escherichia coli in sewage from storm tank discharges and treated effluent processed by a UV-disinfection plant following activated sludge treatment and studied the fate of these microorganisms in an oyster harvesting area impacted by frequent stormwater discharges and infrequent freshwater discharges. Oyster monitoring sites were positioned at intervals downstream from the wastewater treatment works (WwTW) outfall impacting the harvesting area. The decay rates of NoV in oysters as a function of the distance from the outfall were less rapid than those for E. coli that had concentrations of NoV of the same order of magnitude and were over 7 km away from the outfall. Levels of E. coli in oysters from more tidally influenced areas of the estuary were higher around high water than around low water, whereas tidal flows had no influence on NoV contamination in the oysters. The study provides comparative data on the contamination profiles and loadings of NoV and E. coli in a commercial oyster fishery impacted by a WwTW.