Occurrence of Norovirus and Hepatitis A Virus in Wild Mussels Collected from the Baltic Sea

The aim of the study was to define the occurrence of human noroviruses of genogroup I and II (NoV GI and NoV GII) and hepatitis A virus (HAV) in the Baltic Sea mussels. The shellfish samples were taken at the sampling sites located on the Polish coast. In total, 120 shellfish were tested as pooled samples using RT-PCR and hybridisation with virus specific probes. NoV GI was detected in 22 (18.3 %), NoV GII in 28 (23.3 %), and HAV in 9 (7.5 %) of the shellfish. The nucleotide sequence analysis of the detected NoV GII strains showed a 97.3–99.3 % similarity to GII.4 virus strain. This is the first report describing the NoV and HAV occurrence in wild Baltic mussels and their possible role as bioindicators of seawater contamination with human enteric viruses.     

A 1-Year Study on the Detection of Human Enteric Viruses in New Caledonia

Human enteric viruses occur in high concentrations in wastewater and can contaminate receiving environmental waters. Due to the lack of data on the prevalence of enteric viruses in New Caledonia, the presence and the concentrations of enteric viruses in wastewater and seawater were determined. Untreated wastewater and seawater samples were collected monthly for 1 year from a wastewater treatment plant (WWTP) and from the WWTP’s outlet, located directly on a popular recreational beach. Samples were tested for norovirus genogroups I and II (NoV GI and GII), astroviruses (AsV), sapoviruses (SaV), enteroviruses (EV), hepatitis A viruses (HAV), rotaviruses (RoV), human adenoviruses (HAdV) and human polyomaviruses (HPyV). To support these data, faecal samples from cases of gastroenteritis were tested for the first time for NoV and detected in the population. NoV GI, NoV GII, EV, SaV, HAdV and HPyV were detected in all wastewaters, RoV in 75 % and AsV in 67 %. HAV were not detected in wastewater. Overall, 92 % of seawater samples were positive for at least one virus. HPyV were detected most frequently in 92 % of samples and at concentrations up to 7.7 × 10³ genome copies/L. NoV GI, NoV GII, EV, SaV, RoV and HAdV were found in 33, 66, 41, 33, 16 and 66 % of seawater samples, respectively. AsV were not detected in seawater. This study reports for the first time the presence of NoV and other enteric viruses in New Caledonia and highlights the year-round presence of enteric viruses in the seawater of a popular beach.     

Prevalence of Human Noroviruses in Frozen Marketed Shellfish,Red Fruits and Fresh Vegetables

Noroviruses (NoVs), currently recognised as the most common human food-borne pathogens, are ubiquitous in the environment and can be transmitted to humans through multiple foodstuffs. In this study, we evaluated the prevalence of human NoV genogroups I (GI) and II (GII) in 493 food samples including soft red fruits (n = 200), salad vegetables (n = 210) and bivalve mollusc shellfish (n = 83), using the Bovine Enterovirus type 1 as process extraction control for the first time. Viral extractions were performed by elution concentration and genome detection by TaqMan Real-Time RT-PCR (RT-qPCR). Experimental contamination using hepatitis A virus (HAV) was used to determine the limit of detection (LOD) of the extraction methods. Positive detections were obtained from 2 g of digestive tissues of oysters or mussels kept for 16 h in seawater containing 2.0–2.7 log₁₀ plaque-forming units (PFU)/L of HAV. For lettuces and raspberries, the LOD was, respectively, estimated at 2.2 and 2.9 log₁₀ PFU per 25 g. Of the molluscs tested, 8.4 and 14.4 % were, respectively, positive for the presence of GI NoV and GII NoV RNA. Prevalence in GI NoVs varied from 11.9 % for the salad vegetables samples to 15.5 % for the red soft fruits. Only 0.5 % of the salad and red soft fruits samples were positive for GII NoVs. These results highlight the high occurrence of human NoVs in foodstuffs that can be eaten raw or after a moderate technological processing or treatment. The determination of the risk of infection associated with an RT-qPCR positive sample remains an important challenge for the future.     

The presence of Genogroup II Norovirus in Retail Shellfish from Seven Coastal Cities in China

Noroviruses (NoVs) are commonly occurring pathogens that cause gastroenteritis. Outbreaks of viral diseases have often been ascribed to the consumption of contaminated shellfish. Our objective was to evaluate the presence and contamination levels of NoV in shellfish sold at seafood markets in China. We tested 840 shellfish samples (Crassostrea gigas, Mytilus edulis, Azumapecten farreri, SinoNoVacula constricta, Scapharca subcrenata, Ruditapes philippinarum) that were collected from seven cities around the Yellow and Bohai Seas in China between December 2009 and November 2011. We used real-time RT-PCR to detect NoV in purified concentrates from the stomach and digestive diverticula of these shellfish. NoV was detected in 19.35 % (N = 155), 16.67 % (N = 114), 5.70 % (N = 158), 8.82 % (N = 136), 13.74 % (N = 131), and 16.44 % (N = 146) of oyster, mussel, scallop, razor clam, ark shell, and clam samples, respectively. The average detection rate was 13.33 % (112/840). Nucleotide sequencing of the NoV RT-PCR products demonstrated that all strains belonged to NoV genotype GII.12, except two that belonged to GI.3. More than 10² copies of the NoV genome were detected in 69 of 112 positive shellfish samples. Our results suggest that ~13 % of shellfish harbor NoV, and GII.12 NoV is the primary strain in shellfish purchased at markets in seven coastal cities in China.     

GIV Noroviruses in Wastewaters and in Stool Specimens from Hospitalized Patients

Noroviruses (NoVs) are important human pathogens associated with foodborne and waterborne gastroenteritis. These viruses are genetically highly heterogeneous, with more than forty genotypes within three genogroups (GI, GII, and GIV) identified in humans. However, the vast majority of human infections are associated with variants of a unique genotype, GII.4. Aside from these NoV strains of epidemiological relevance, NoV strains of genogroup GIV (Alphatron-like) are reported in a sporadic fashion and their overall prevalence in the community is unknown and this likely reflects the lack of specific diagnostic tools. We analyzed raw sewages collected from 32 wastewater treatment plants distributed throughout Italy (307 samples) and stool specimens collected from hospitalized patients with clinical signs of diarrhea of unknown etiology (285 samples). By using specific qualitative and quantitative RT-PCR assays, 21.8 % of the sewage samples and 3.2 % of the stool specimens tested positive for GIV NoVs. The number of genome copies in fecal samples ranged from 5.08 × 10⁴ to 1.73× 10⁶/g of feces. Sequence analysis showed limited genetic variability in human GIV viruses. The presence of GIV NoV both in sewage and in clinical samples confirms that not only GI and GII NoVs but also GIV strains are circulating in humans. Monitoring of GIV NoV is recommended in order to understand the dynamics of circulation in human populations, environmental contamination, and potential health risks.     

Environmental Surveillance for Noroviruses in Selected South African Wastewaters 2015–2016: Emergence of the Novel GII.17

Norovirus (NoV) GII.4 is the predominant genotype associated with gastroenteritis pandemics and new strains emerge every 2–3 years. Between 2008 and 2011, environmental studies in South Africa (SA) reported NoVs in 63% of the sewage-polluted river water samples. The aim of this study was to assess whether wastewater samples could be used for routine surveillance of NoVs, including GII.4 variants. From April 2015 to March 2016, raw sewage and effluent water samples were collected monthly from five wastewater treatment plants in SA. A total of 108 samples were screened for NoV GI and GII using real-time RT-qPCR. Overall 72.2% (78/108) of samples tested positive for NoVs with 4.6% (5/108) GI, 31.5% (34/108) GII and 36.1% (39/108) GI + GII strains being detected. Norovirus concentrations ranged from 1.02 × 10² to 3.41 × 10⁶ genome copies/litre for GI and 5.00 × 10³ to 1.31 × 10⁶ genome copies/litre for GII. Sixteen NoV genotypes (GI.2, GI.3, GI.4, GI.5, GI.6, GII.2, GII.3, GII.4, GII.7, GII.9, GII.10, GII.14, GII.16, GII.17, GII.20, and GII.21) were identified. Norovirus GII.2 and GII.17 co-dominated and the majority of GII.17 strains clustered with the novel Kawasaki 2014 variant. Sewage surveillance facilitated detection of Kawasaki 2014 in SA, which to date has not been detected with surveillance in children with gastroenteritis <5 years of age. Combined surveillance in the clinical setting and environment appears to be a valuable strategy to monitor emergence of NoV strains in countries that lack NoV outbreak surveillance.     

Molecular Detection of human Noroviruses in Influent and Effluent Samples From Two Biological Sewage Treatment Plants in the Region of Monastir,Tunisia

Noroviruses (NoVs) are responsible for numerous cases of waterborne and foodborne gastroenteritis every year. They are released in the sewage and their detection in this environment can reflect the epidemiology of the viral strains circulating in the community. A three-year (2007–2010) survey was conducted in order to evaluate the presence of human NoVs using RT-PCR in 518 sewage samples collected at the entrance and exit of two biological sewage treatment plants located in Monastir region, Tunisia. In this study, we aimed to genetically characterize the most prevalent GI and GII NoV strains, in order to obtain a rough estimate of the efficacy of disinfection treatments and to compare the results with clinical data documented in the same area during the same period. This work confirms the wide circulation and the genetic diversity of NoVs in Tunisia and the widespread distribution of NoV variants in both raw and treated wastewater. Indeed, NoV was detected in 192 (37.1 %) sewage samples, among them mixed infections with group A rotavirus were detected in 125 (65.1 %) cases. The genotypes of the GI NoVs were GI.1, GI.2, GI.4, GI.5, and GI of unassigned genotype (GI.UA), and the genotypes of the GII NoVs were all GII.12. This study enhances the currently poor environmental virological data gathered in Tunisia, demonstrates the benefit of environmental surveillance as a tool to determine the epidemiology of NoVs circulating in a given community, and underlines the need for the design and support of similar long-term studies in our country, in order to compensate for the absence of a national surveillance system for gastroenteric viruses.     

Detection of Norovirus GII.17 Kawasaki 2014 in Shellfish,Marine Water and Underwater Sewage Discharges in Italy

Norovirus (NoV) is a major cause of non-bacterial acute gastroenteritis worldwide, and the variants of genotype GII.4 are currently the predominant human strains. Recently, a novel variant of NoV GII.17 (GII.P17_GII.17 NoV), termed Kawasaki 2014, has been reported as the cause of gastroenteritis outbreaks in Asia, replacing the pandemic strain GII.4 Sydney 2012. The GII.17 Kawasaki 2014 variant has also been reported sporadically in patients with gastroenteritis outside of Asia, including Italy. In this study, 384 shellfish samples were subjected to screening for human NoVs using real-time PCR and 259 (67.4%) tested positive for Genogroup II (GII) NoV. Of these, 52 samples, selected as representative of different areas and sampling dates, were further amplified by conventional PCR targeting the capsid gene, using broad-range primers. Forty shellfish samples were characterized by amplicon sequencing as GII.4 (n = 29), GII.2 (n = 4), GII.6 (n = 2), GII.12 (n = 2), and GII.17 (n = 3). Sixty-eight water samples (39 seawater samples from the corresponding shellfish production areas and 29 water samples from nearby underwater sewage discharge points) were also tested using the above broad-range assay: eight NoV-positive samples were characterized as GII.1 (n = 3), GII.2 (n = 1), GII.4 (n = 2), and GII.6 (n = 2). Based on full genome sequences available in public databases, a novel RT-PCR nested assay specific for GII.17 NoVs was designed and used to re-test the characterized shellfish (40) and water (8) samples. In this second screening, the RNA of GII.17 NoV was identified in 17 additional shellfish samples and in one water sample. Upon phylogenetic analysis, these GII.17 NoV isolates were closely related to the novel GII.17 Kawasaki 2014. Interestingly, our findings chronologically matched the emergence of the Kawasaki 2014 variant in the Italian population (early 2015), as reported by hospital-based NoV surveillance. These results, showing GII.17 NoV strains to be widespread in shellfish samples collected in 2015 in Italy, provide indirect evidence that this strain has started circulating in the Italian population. Notably, using a specific assay, we were able to detect many more samples positive for GII.17 NoV, indicating that, in food and water matrices, broad-range assays for NoV may grossly underestimate the prevalence of some, less common, NoVs. The detection of the GII.17 strain Kawasaki 2014 in clinical, water and food samples in Italy highlights the need for more systematic surveillance for future disease control and prevention.     

Evaluation of a Porcine Gastric Mucin and RNase A Assay for the Discrimination of Infectious and Non-infectious GI.1 and GII.4 Norovirus Following Thermal,Ethanol, or Levulinic Acid Plus Sodium Dodecyl Sulfate Treatments

Human noroviruses (NoVs) are a major source of foodborne illnesses worldwide. Since human NoVs cannot be cultured in vitro, methods that discriminate infectious from non-infectious NoVs are needed. The purpose of this study was to evaluate binding of NoV genotypes GI.1 and GII.4 to histo-blood group antigens expressed in porcine gastric mucin (PGM) as a surrogate for detecting infectious virus following thermal (99 °C/5 min), 70 % ethanol or 0.5 % levulinic acid (LV) plus 0.01 or 0.1 % sodium dodecyl sulfate (SDS) sanitizer treatments and to determine the limit of detection of GI.1 and GII.4 binding to PGM. Treated and control virus samples were applied to 96-well plates coated with 1 µg/ml PGM followed by RNase A (5 ng/µl) treatment for degradation of exposed RNA. Average log genome copies per ml (gc/ml) reductions and relative differences (RD) in quantification cycle (Cq) values after thermal treatment were 1.77/5.62 and 1.71/7.25 (RNase A) and 1.73/5.50 and 1.56/6.58 (no RNase A) for GI.1 and GII.4, respectively. Treatment of NoVs with 70 % EtOH resulted in 0.05/0.16 (GI.1) and 3.54/10.19 (GII.4) log reductions in gc/ml and average RD in Cq value, respectively. LV (0.5 %) combined with 0.1 % SDS provided a greater decrease of GI.1 and GII.4 NoVs with 8.97 and 8.13 average RD in Cq values obtained, respectively than 0.5 % LV/0.01 % SDS. Virus recovery after PGM binding was variable with GII.4 > GI.1. PGM binding is a promising surrogate for identifying infectious and non-infectious NoVs after capsid destruction, however, results vary depending on virus strain and inactivation method.     

Prevalence of Human Parainfluenza Viruses and Noroviruses Genomes on Office Fomites

The aim of this study was to evaluate the potential role of office fomites in respiratory (human parainfluenza virus 1—HPIV1, human parainfluenza virus 3—HPIV3) and enteric (norovirus GI—NoV GI, norovirus GII—NoV GII) viruses transmission by assessing the occurrence of these viruses on surfaces in office buildings. Between 2016 and 2017, a total of 130 surfaces from open-space and non-open-space rooms in office buildings located in one city were evaluated for HPIV1, HPIV3, NoV GI, and NoV GII viral RNA presence. Detection of viruses was performed by RT-qPCR method. Study revealed 27 positive samples, among them 59.3% were HPIV3-positive, 25.9% HPIV1-positive, and 14.8% NoV GII-positive. All tested surfaces were NoV GI-negative. Statistical analysis of obtained data showed that the surfaces of office equipment including computer keyboards and mice, telephones, and desktops were significantly more contaminated with respiratory viruses than the surfaces of building equipment elements such as door handles, light switches, or ventilation tracts (χ ² p = 0.006; Fisher’s Exact p = 0.004). All examined surfaces were significantly more contaminated with HPIVs than NoVs (χ ² p = 0.002; Fisher’s Exact p = 0.003). Office fomites in open-space rooms were more often contaminated with HPIVs than with NoVs (χ ² p = 0.016; Fisher’s Exact p = 0.013). The highest average concentration of HPIVs RNA copies was observed on telephones (1.66 × 10² copies/100 cm²), while NoVs on the light switches (1.40 × 10² copies/100 cm²). However, the Kruskal–Wallis test did not show statistically significant differences in concentration levels of viral RNA copies on surfaces between the all tested samples. This study unequivocally showed that individuals in office environment may have contact with both respiratory and enteric viral particles present on frequently touched surfaces.     

Prevalence and Molecular Genotyping of Noroviruses in Market Oysters,Mussels, and Cockles in Bangkok,Thailand

Noroviruses are the most common cause of acute gastroenteritis associated with bivalve shellfish consumption. This study aimed to detect and characterize noroviruses in three bivalve shellfish species: oysters (Saccostrea forskali), cockles (Anadara nodifera), and mussels (Perna viridis). The virus concentration procedure (adsorption-twice elution-extraction) and a molecular method were employed to identify noroviruses in shellfish. RT-nested PCR was able to detect known norovirus GII.4 of 8.8 × 10^?2 genome copies/g of digestive tissues from oyster and cockle concentrates, whereas in mussel concentrates, the positive result was seen at 8.8 × 10² copies/g of digestive tissues. From August 2011 to July 2012, a total of 300 shellfish samples, including each of 100 samples from oysters, cockles, and mussels were collected and tested for noroviruses. Norovirus RNA was detected in 12.3 % of shellfish samples. Of the noroviruses, 7.7 % were of the genogroup (G) I, 2.6 % GII, and 2.0 % were mixed GI and GII. The detection rate of norovirus GI was 2.1 times higher than GII. With regards to the different shellfish species, 17 % of the oyster samples were positive, while 14.0 and 6.0 % were positive for noroviruses found in mussels and cockles, respectively. Norovirus contamination in the shellfish occurred throughout the year with the highest peak in September. Seventeen norovirus-positive PCR products were characterized upon a partial sequence analysis of the capsid gene. Based on phylogenetic analysis, five different genotypes of norovirus GI (GI.2, GI.3, GI.4, GI.5, and GI.9) and four different genotypes of GII (GII.1, GII.2, GII.3, and GII.4) were identified. These findings indicate the prevalence and distribution of noroviruses in three shellfish species. The high prevalence of noroviruses in oysters contributes to the optimization of monitoring plans to improve the preventive strategies of acute gastroenteritis.     

Viruses Surveillance Under Different Season Scenarios of the Negro River Basin,Amazonia, Brazil

The Negro River is located in the Amazon basin, the largest hydrological catchment in the world. Its water is used for drinking, domestic activities, recreation and transportation and water quality is significantly affected by anthropogenic impacts. The goals of this study were to determine the presence and concentrations of the main viral etiological agents of acute gastroenteritis, such as group A rotavirus (RVA) and genogroup II norovirus (NoV GII), and to assess the use of human adenovirus (HAdV) and JC polyomavirus (JCPyV) as viral indicators of human faecal contamination in the aquatic environment of Manaus under different hydrological scenarios. Water samples were collected along Negro River and in small streams known as igarapés. Viruses were concentrated by an organic flocculation method and detected by quantitative PCR. From 272 samples analysed, HAdV was detected in 91.9 %, followed by JCPyV (69.5 %), RVA (23.9 %) and NoV GII (7.4 %). Viral concentrations ranged from 10² to 10⁶ GC L^?1 and viruses were more likely to be detected during the flood season, with the exception of NoV GII, which was detected only during the dry season. Statistically significant differences on virus concentrations between dry and flood seasons were observed only for RVA. The HAdV data provides a useful complement to faecal indicator bacteria in the monitoring of aquatic environments. Overall results demonstrated that the hydrological cycle of the Negro River in the Amazon Basin affects the dynamics of viruses in aquatic environments and, consequently, the exposure of citizens to these waterborne pathogens.     

Semi-Direct Lysis of Swabs and Evaluation of Their Efficiencies to Recover Human Noroviruses GI and GII from Surfaces

Enteric viruses such as noroviruses (NoVs) continue to be the cause of widespread viral outbreaks due to person-to-person transmission, contaminated food, and contaminated surfaces. In order to optimize swabbing methodology for the detection of viruses on (food) contact surfaces, three swab elution/extraction strategies were compared in part one of this study, out of which, one strategy was based on the recently launched ISO protocol (ISO/TS 15216-1) for the determination of hepatitis A virus and NoV in food using real-time RT-PCR (RT-qPCR). These three swab elution/extraction strategies were tested for the detection of GI.4 and GII.4 NoV on high-density polyethylene (HD-PE) surfaces with the use of cotton swabs. For detection of GI.4 and GII.4, the sample recovery efficiency (SRE) obtained with the direct lysis strategy (based on ISO/TS 15216-1) was significantly lower than the SRE obtained with both other strategies. The semi-direct lysis strategy was chosen to assess the SRE of two common swabs (cotton swab and polyester swab) versus the biowipe (Biomérieux, Lyon, France) on three surfaces (HD-PE, neoprene rubber (NR), and nitrile gloves (GL)). For both surfaces, HD-PE and GL, no significant differences in SREs of GI.4 and GII.4 NoVs were detected between the three different swabs. For the coarser NR, biowipes turned out to be the best option for detecting both GI.4 and GII.4 NoV.     

Comprehensive Study on Enteric Viruses and Indicators in Surface Water in Kyoto,Japan, During 2014–2015 Season

Certain enteric viruses that are present in the water environment are potential risk factors of waterborne infections. To better understand the impact of viruses in water, both enteric viruses and their potential indicators should be comparatively investigated. In this study, occurrences of GI- and GII-noroviruses (NoVs), sapovirus (SaV), rotavirus (RoV), Aichi virus 1 (AiV-1), enterovirus (EV), and pepper mild mottle virus (PMMoV) were quantitatively determined in surface water samples in Japan. Additionally, the genotype distribution of GI- and GII-NoVs was determined using a next-generation amplicon sequencing. PMMoV was the most abundant virus regardless of season and location, indicating its usefulness as an indicator for the viral contamination of water. Other potential indicators, AiV and EV, were less abundant than GII-NoV. Viruses other than PMMoV showed seasonality, i.e., EV and other viruses (NoVs, SaV, RoV, and AiV-1) became prevalent during summer and winter, respectively. SaV showed a relatively high abundance at a location that was affected by untreated wastewater. Regarding NoV genotypes, GI.1, GI.2, GI.4, GI.5, GI.6, GII.3, GII.4, GII.6, and GII.17 were found from the surface water samples. GII.4 and GII.17 seemed to have contributed to the high abundance of GII-NoV in the samples. Interestingly, GII.17 strains became prevalent in the water samples before becoming prevalent among gastroenteritis patients in Japan. These findings provide further insights into the properties of viruses as contaminants in the water environment.     

Simple and Rapid Detection of Human Norovirus from Produce Using SYBR Green I-based Real-time RT-PCR

Several foodborne norovirus gastroenteritis outbreaks have been linked to fresh produce. Rapid and sensitive detection can help prevent the release of contaminated produce items in the market. The objectives of this study were to apply a relatively inexpensive SYBR Green I-based real-time RT-PCR assay for the rapid detection of human norovirus (NoV) GI and GII on the surfaces of lettuce, cherry tomatoes, and green onions. Each washed produce commodity (25 g) was spiked with serial dilutions of NoV GI and GII stool samples. RNA was eluted from the produce surface and extracted using the TRIzol^? method. This was followed by detection using SYBR Green I real-time RT-PCR with primers specific for NoV GI (COG1F-COG1R) and GII (COG2F-COG2R) along with an internal RNA amplification control. End-point detection limits from lettuce and tomatoes were found to be 10 RT-PCR units/25 g for GI and GII and 1 RT-PCR unit/25 g for GI and 10 RT-PCR units/25 g for GII from green onions. These results were confirmed by Tm analysis (showing peaks at 81.5 and 84°C for GI and GII, respectively; and 83°C for the IAC) as well as agarose gel electrophoresis that confirmed products of ~95 bp for GI and GII and ~155 bp for the RNA IAC. Results could be obtained within one working day, showing potential for routine use in diagnostics and monitoring of NoV contamination by the produce industry.     

Critical Review on the Public Health Impact of Norovirus Contamination in Shellfish and the Environment: A UK Perspective

We review the risk of norovirus (NoV) infection to the human population from consumption of contaminated shellfish. From a UK perspective, risk is apportioned for different vectors of NoV infection within the population. NoV spreads mainly by person-to-person contact or via unsanitary food handling. NoV also enters the coastal zone via wastewater discharges resulting in contamination of shellfish waters. Typically, NoV persists in the marine environment for several days, with its presence strongly linked to human population density, wastewater discharge rate, and efficacy of wastewater treatment. Shellfish bioaccumulate NoV and current post-harvest depuration is inefficient in its removal. While NoV can be inactivated by cooking (e.g. mussels), consumption of contaminated raw shellfish (e.g. oysters) represents a risk to human health. Consumption of contaminated food accounts for 3–11% of NoV cases in the UK (~74,000 cases/year), of which 16% are attributable to oyster consumption (11,800 cases/year). However, environmental and human factors influencing NoV infectivity remain poorly understood. Lack of standard methods for accurate quantification of infective and non-infective (damaged) NoV particles represent a major barrier, hampering identification of an appropriate lower NoV contamination limit for shellfish. Future management strategies may include shellfish quality assessment (at point of harvest or at point of supply) or harvesting controls. However, poor understanding of NoV inactivation in shellfish and the environment currently limits accurate apportionment and risk assessment for NoV and hence the identification of appropriate shellfish or environmental quality standards.