Depuration decay rates for NoV derived from data in Doré <i>et al</i> [33].

<p>Depuration decay rates for NoV derived from data in Doré <i>et al</i> [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0193865#pone.0193865.ref033" target="_blank">33</a>].</p

Parameter definitions.

<p>Parameter definitions.</p

Pre-depuration (a) and during depuration (b) probability distributions, with NoV cpg, and <i>σ</i>₀ = 1.645.

<p>This variability corresponds to the worst case scenario where <i>φ</i> = 95% (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0193865#pone.0193865.e014" target="_blank">Eq 5</a>). Fig (a) splits the distribution’s area into four sections, and states probabilities for each section. Fig (b) shows probability distributions at <i>t</i> = 0 hrs (<b>——</b>), <i>t</i> = 50 hrs (<b>– – –</b>), <i>t</i> = 100 hrs (⋯) induced by depuration decay rate <i>b</i> = 0.01339. Note the different vertical axis scales. Inset bar plot shows the respective changes in section probabilities for each time point corresponding to domain values in Fig 1(a).</p

Minimum depuration times (<i>T</i>_WCV) for varying decay rates and NoV assurance levels.

<p>Simulated NoV test results of 10-oyster homogenates, which had undergone depuration using each parameter set {<i>b</i>, <i>φ</i>, <i>T</i>_WCV} are shown. Times are in hours.</p

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