Noroviruses, an important cause of gastroenteritis, are excreted by infected individuals and are therefore present in wastewater. We quantified norovirus genogroup I (GI) and GII in wastewater at different locations in France and evaluated removal by a range of treatment types, including basic (waste stabilization pond), current industry standard (activated sludge), and state-of-the-art (submerged membrane bioreactor) treatments. Noroviruses were quantified using real-time reverse transcription-PCR (rRT-PCR). Mengovirus was used as a virus extraction control, and internal controls were used to verify the level of GI and GII rRT-PCR inhibition. A total of 161 (81 influent and 79 effluent) samples were examined; GI and GII were detected in 43 and 88% of the influent samples, respectively, and in 24 and 14% of the effluent samples, respectively. Physicians in France report far more cases of GII than GI during outbreaks; thus, the frequent presence of GI was unexpected. The GI influent concentrations were more variable, the peak GI influent concentrations were higher than the peak GII influent concentrations at all four sites (up to 1 ؋ 10 9 and 6 ؋ 10 7 genome copies/liter, respectively), and the average positive influent concentrations of GI were higher than the average positive influent concentrations of GII. The maximum effluent breakthrough concentrations were 6 ؋ 10 6 and 3 ؋ 10 6 genome copies/liter for GI and GII, respectively, indicating that the four treatment systems studied decreased the norovirus contamination load in receiving waters.Noroviruses, the leading cause of gastroenteritis worldwide, are extremely genetically diverse (2, 5, 33). Members of the Caliciviridae family, they are subdivided into five genogroups (genogroup I [GI], GII, GIII, GIV, and GV), and GI, GII, and GIV have been detected in humans (42). GII has been shown to account for the majority (up to 92%) of reported norovirus gastroenteritis cases, and GI accounts for the large majority of the remaining cases (2,5,22). Norovirus infections occur throughout the year, but there is a large annual peak of gastroenteritis during the cold winter months (27). Although the illness is generally self-limiting in otherwise healthy individuals, the high incidence of norovirus cases imposes a high cost on society (24). Besides person-to-person transmission, food contaminated by sewage, such as oysters, berries, or water, has been implicated in outbreaks, although often the source cannot be determined (10,33,41). Noroviruses have been shown to be resistant to wastewater treatment (17,28,30,36,38,39) and have been detected in wastewater-polluted water, as well as shellfish (19,20,26,36).Currently, molecular detection is the only method for detection of noroviruses, but their genetic diversity has made genomic detection of these viruses a challenge (1, 2). Recently developed broadly reactive one-step real-time reverse transcription PCR (rRT-PCR) assays have allowed sensitive detection (13,21,35,37), although precise quantification of environmental sam...

Following a flooding event close to a shellfish production lagoon, 205 cases of gastroenteritis were linked to oyster consumption. Twelve stool samples from different individuals were collected. Analysis showed that eight samples were positive for multiple enteric viruses, and one stool sample had seven different enteric viruses. Analysis of shellfish implicated in the outbreak allowed detection of the same diversity of enteric viruses, with some viral genomic sequences being identical to those obtained from stool sample analysis. Shellfish were contaminated by as many as five different enteric viruses. For the first time in Europe, Aichi virus was identified in oyster samples. Shellfish samples collected over 3 weeks following the outbreak showed a progressive decline in the level of virus contamination as measured by the virus diversity detected and by quantitative reverse transcription-PCR.

Bivalve molluscan shellfish, such as oysters, filter large volumes of water as part of their feeding activities and are able to accumulate and concentrate different types of pathogens, particularly noroviruses, from fecal human pollution. Based on our previous observation of a specific binding of the Norwalk strain (prototype norovirus genogroup I) to the oyster digestive tract through an A-like carbohydrate structure indistinguishable from human blood group A antigen and on the large diversity between strains in terms of carbohydrate-binding specificities, we evaluated the different ligands implicated in attachment to oysters tissues of strains representative of two main genogroups of human norovirus. The GI.1 and GII.4 strains differed in that the latter recognized a sialic acid-containing ligand, present in all tissues, in addition to the A-like ligand of the digestive tract shared with the GI.1 strain. Furthermore, bioaccumulation experiments using wild-type or mutant GI.1 Viruslike particles showed accumulation in hemocytes largely, but not exclusively, based on interaction with the A-like ligand. Moreover, a seasonal effect on the expression of these ligands was detected, most visibly for the GI.1 strain, with a peak in late winter and spring, a period when GI strains are regularly involved in oyster-related outbreaks. These observations may explain some of the distinct epidemiological features of strains from different genogroups.

Pollution of coastal waters can result in contamination of

To evaluate membrane bioreactor wastewater treatment virus removal, a study was conducted in southwest France. Samples collected from plant influent, an aeration basin, membrane effluent, solid sludge, and effluent biweekly from October 2009 to June 2010 were analyzed for calicivirus (norovirus and sapovirus) by real-time reverse transcription-PCR (RT-PCR) using extraction controls to perform quantification. Adenovirus and Escherichia coli also were analyzed to compare removal efficiencies. In the influent, sapovirus was always present, while the norovirus concentration varied temporally, with the highest concentration being detected from February to May. All three human norovirus genogroups (GI, GII, and GIV) were detected in effluent, but GIV was never detected in effluent; GI and GII were detected in 50% of the samples but at low concentrations. In the effluent, sapovirus was identified only once. An adenovirus titer showing temporal variation in influent samples was identified only twice in effluent. E. coli was always below the limit of detection in the effluent. Overall, the removal of calicivirus varied from 3.3 to greater than 6.8 log units, with no difference between the two main genogroups. Our results also demonstrated that the viruses are blocked by the membrane in the treatment plant and are removed from the plant as solid sludge.