Article pubs.acs.org/est
Fate of Human Noroviruses in Shellfish and Water Impacted by Frequent Sewage Pollution Events Carlos J.A. Campos,* Justin Avant, Nicole Gustar, James Lowther, Andy Powell, Louise Stockley, and David N. Lees Weymouth Laboratory, Centre for Environment, Fisheries and Aquaculture Science (Cefas), Dorset DT4 8UB, U.K. S Supporting Information *
ABSTRACT: 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.
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INTRODUCTION Human illness associated with eating raw molluscan shellfish occurs worldwide1−3 and is associated with the harvesting of shellfish in coastal waters contaminated with sewage pollution. Sewage discharges contain high numbers of enteric bacteria and viruses,4,5 which are accumulated by bivalve shellfish during filter-feeding.6,7 The epidemiological evidence indicates that the majority of cases of shellfish-related gastroenteritis are caused by human noroviruses (NoV).1,8 Worldwide, legislation aimed at reducing the risk of infection from sewage-contaminated molluscan shellfish has historically relied on the monitoring of fecal indicator organisms (FIO) in shellfish or growing waters to indicate the likely risk of fecal contamination.8,9 Shellfish from contaminated areas are either prevented from being harvested, purified in artificial tanks (depuration) or in the natural environment (relaying), or commercially cooked. An internationally accepted standard of
