Human norovirus contamination in water sources: A systematic review and meta-analysis

Human intestinal enteroids platform to assess the infectivity of gastroenteritis viruses in wastewater

Fecal-orally transmitted gastroenteritis viruses, particularly human noroviruses (HuNoVs), are a public health concern. Viral transmission risk through contaminated water results underexplored as they have remained largely unculturable until recently and the robust measuring of gastroenteritis viruses infectivity in a single cell line is challenging. This study primarily aimed to test the feasibility of the human intestinal enteroids (HIE) model to demonstrate the infectivity of multiple gastroenteritis viruses in wastewater. Initially, key factors affecting viral replication in HIE model were assessed, and results demonstrated that the reagent-assisted disruption of 3D HIE represents an efficient alternative to syringe pass-through, and the filtering of HuNoV stool suspensions could be avoided. Moreover, comparable replication yields of clinical strains of HuNoV genogroup I (GI), HuNoV GII, rotavirus (RV), astrovirus (HAstV), and adenoviruses (HAdV) were obtained in single and multiple co-infections. Then, the optimized HIE model was used to demonstrate the infectivity of multiple naturally occurring gastroenteritis viruses from wastewater. Thus, a total of 28 wastewater samples were subjected to (RT)-qPCR for each virus, with subsequent testing on HIE. Among these, 16 samples (57 %) showed replication of HuNoVs (n = 3), RV (n = 5), HAstV (n = 8), and/or HAdV (n = 5). Three samples showed HuNoV replication, and sequences assigned to HuNoV GI.3[P13] and HuNoV GII.4[P16] genotypes. Concurrent replication of multiple gastroenteritis viruses occurred in 4 wastewater samples. By comparing wastewater concentrate and HIE supernatant sequences, diverse HAstV and HAdV genotypes were identified in 4 samples. In summary, we successfully employed HIE to demonstrate the presence of multiple infectious human gastroenteritis viruses, including HuNoV, in naturally contaminated wastewater samples.

Improving the Detection and Understanding of Infectious Human Norovirus in Food and Water Matrices: A Review of Methods and Emerging Models

Human norovirus (HuNoV) is a leading global cause of viral gastroenteritis, contributing to numerous outbreaks and illnesses annually. However, conventional cell culture systems cannot support the cultivation of infectious HuNoV, making its detection and study in food and water matrices particularly challenging. Recent advancements in HuNoV research, including the emergence of models such as human intestinal enteroids (HIEs) and zebrafish larvae/embryo, have significantly enhanced our understanding of HuNoV pathogenesis. This review provides an overview of current methods employed for HuNoV detection in food and water, along with their associated limitations. Furthermore, it explores the potential applications of the HIE and zebrafish larvae/embryo models in detecting infectious HuNoV within food and water matrices. Finally, this review also highlights the need for further optimization and exploration of these models and detection methods to improve our understanding of HuNoV and its presence in different matrices, ultimately contributing to improved intervention strategies and public health outcomes.

Microbiological hazard identification in river waters used for recreational activities

Pathogenic bacteria, viruses, and parasites can cause waterborne disease outbreaks. The study of coastal water quality contributes to identifying potential risks to human health and to improving water management practices. The Río de la Plata River, a wide estuary in South America, is used for recreational activities, as a water source for consumption and as a site for sewage discharges. In the present study, as the first step of a quantitative microbial risk assessment of the coastal water quality of this river, a descriptive study was performed to identify the microbial pathogens prevalent in its waters and in the sewage discharged into the river. Two sites, representing two different potential risk scenarios, were chosen: a heavily polluted beach and an apparently safe beach. Conductivity and fecal contamination indicators including enterococci, Escherichia coli, F + RNA bacteriophages, and human polyomaviruses showed high levels. Regarding enterococci, differences between sites were significant (p-values <0.001). 93.3% and 56.5% of the apparently safe beach exceeded the recreational water limits for E. coli and enterococci. Regarding pathogens, diarrheagenic E. coli, Salmonella, and noroviruses were detected with different frequencies between sites. The parasites Cryptosporidium spp. and Giardia duodenalis were frequently detected in both sites. The results regarding viral, bacterial, and parasitic pathogens, even without correlation with conventional indicators, showed the importance of monitoring a variety of microorganisms to determine water quality more reliably and accurately, and to facilitate further studies of health risk assessment. The taxonomic description of microbial pathogens in river waters allow identifying the microorganisms that infect the population living on its shores but also pathogens not previously reported by the clinical surveillance system.

Viral gastroenteritis

Since the discovery of norovirus in 1972 as a cause of what was contemporarily known as acute infectious non-bacterial gastroenteritis, scientific understanding of the viral gastroenteritides has continued to evolve. It is now recognised that a small number of viruses are the predominant cause of acute gastroenteritis worldwide, in both high-income and low-income settings. Although treatment is still largely restricted to the replacement of fluid and electrolytes, improved diagnostics have allowed attribution of illness, enabling both targeted treatment of individual patients and prioritisation of interventions for populations worldwide. Questions remain regarding specific genetic and immunological factors underlying host susceptibility, and the optimal clinical management of patients who are susceptible to severe or prolonged manifestations of disease. Meanwhile, the worldwide implementation of rotavirus vaccines has led to substantial reductions in morbidity and mortality, and spurred interest in vaccine development to diminish the impact of the most prevalent viruses that are implicated in this syndrome.

Investigation of two norovirus outbreaks linked to drinking water contaminated with multiple GII strains in a rural county-Chongqing, China, 2021

Backgrounds

Norovirus is leading cause of non-bacterial gastroenteritis outbreaks globally, characterized by different strains prevalent in different countries and regions.

Methods

Cases were defined as individuals experiencing diarrhea ≥3 times/24 h, and/or vomiting ≥2 times/24 h in two villages between January 28 and February 9, 2021. Investigations were conducted to identify causes. Cases were interviewed using a standardized in-person form to collect data on potential risk factors. A retrospective cohort study was conducted to investigate the role of the spring water supply as the outbreak source. Residents from neighboring villages with different water sources served as the unexposed population. Stool specimens, rectal swabs, and water samples were tested using quantitative real-time Polymerase Chain Reaction, with subsequent sequencing performed on pathogen-positive specimens.

Results

Village-specific attack rates were 21.93% (123/561) and 26.99% (88/326), respectively. Evidence from both epidemiological and laboratory tests was consistent. Drinking spring water was statistically associated with the two outbreaks (RR = 41.8 and 79.2, respectively). In both outbreaks, stool specimens, rectal swabs, and water samples tested positive for norovirus. Specifically, GII.2 (P16) and GII.17 (P17) were identified in outbreak A, and GII.4 Sydney (P16) and GII.1 (P16) in outbreak B.

Conclusion

These two independent gastroenteritis outbreaks share similarities, both being linked to norovirus GII strains. The contaminated spring drinking water was identified as the probable source and was promptly closed and subjected to disinfection procedures. These findings reinforce the importance of implementing sanitation and environmental disinfection measures in rural areas, especially during the periods of increased rainfall.

Toward better monitoring of human noroviruses and F-specific RNA bacteriophages in aquatic environments using bivalve mollusks and passive samplers: A case study

Monitoring pathogenic enteric viruses in continental and marine water bodies is essential to control the viral contamination of human populations. Human Noroviruses (NoV) are the main enteric viruses present in surface waters and foodstuff. In a context of global change, it is currently a challenge to improve the management of viral pollutions in aquatic environments and thereby limit the contamination of vulnerable water bodies or foodstuffs. The aim of this study is to evaluate the potential of specific accumulation systems for improving the detection of NoV in water bodies, compared to direct water analyses. Passive samplers (Zetapor filters) and three species of bivalve molluscan shellfish (BMS) (Dreissena polymorpha, Mytilus edulis and Crassostreas gigas) were used as accumulation systems to determine their performance in monitoring continental and marine waters for viruses. F-specific RNA bacteriophages (FRNAPH) were also analyzed since they are described as indicators of NoV hazard in many studies. During a one-year study in a specific area frequently affected by fecal pollution, twelve campaigns of exposure of passive samplers and BMS in continental and coastal waters were conducted. Using suitable methods, NoV (genome) and FRNAPH (infectious and genome) were detected in these accumulation systems and in water at the same time points to determine the frequency of detection but also to gain a better understanding of viral pollution in this area. The reliability of FRNAPH as a NoV indicator was also investigated. Our results clearly showed that BMS were significantly better than passive samplers and direct water analyses for monitoring NoV and FRNAPH contamination in water bodies. A dilution of viral pollution between the continental and the coastal area was observed and can be explained by the distance from the source of the pollution. Viral pollution is clearly greater during the winter period, and stakeholders should take this into consideration in their attempts to limit the contamination of food and water. A significant correlation was once again shown between NoV and FRNAPH genomes in BMS, confirming the reliability of FRNAPH as a NoV indicator. Moreover, a strong correlation was observed between NoV genomes and infectious FRNAPH, suggesting recent viral pollution since infectious particles had not been inactivated at sufficient levels in the environment. More generally, this study shows the value of using BMS as an active method for improving knowledge on the behavior of viral contamination in water bodies, the ranking of the contamination sources, and the vulnerability of downstream water bodies.

Norovirus, Hepatitis A and SARS-CoV-2 surveillance within Chilean rural wastewater treatment plants based on different biological treatment typologies

During the COVID-19 pandemic, wastewater from WWTPs became an interesting source of epidemiological surveillance. However, there is uncertainty about the influence of treatment type on virus removal. The aim of this study was to assess viral surveillance within wastewater treatment plants (WWTPs) based on different biological treatments. Seasonal monitoring (autumn-winter and spring-summer) was conducted in 10 Chilean rural WWTPs, which were based on activated sludge, aerated lagoons, bio-discs, constructed wetlands, vermifilters and mixed systems. Viruses were measured (influent/effluent) by the RT-qPCR technique, using a commercial kit for SARS-CoV-2, NoV GI, NoV GII, and HAV. The detection of SARS-CoV-2 viral variants by genotyping was performed using SARS-CoV-2 Mutation Assays (ThermoFisher Scientific, USA). JC polyomavirus detection (control), as well as a qPCR technique. Results showed that SARS-CoV-2, NoV GI and GII were detected in influents at values between <5 and 462, 0 to 28, and 0 to 75 GC/mL, respectively. HAV was not detected among the studied WWTPs. The monitored WWTPs removed these viruses at percentages between 0 and 100 %. WWTPs based on activated sludge with bio-discs demonstrated to be the most efficient at removing SARS-CoV-2 (up to 98 %) and NoV GI and GII (100 %). Meanwhile, bio-discs technologies were the least efficient for viral removal, due to biofilm detachment, which could also adsorb viral aggregates. A correlation analysis established that solids, pH, and temperature are the most influential parameters in viral removal. Wastewater-based surveillance at WWTP allowed for the detection of Omicron before the Chilean health authorities notified its presence in the population. In addition, surveillance of viruses and other microorganisms could help assess the potential public health risk of wastewater recycling.

Persistence of Human Norovirus (GII) in Surface Water: Decay Rate Constants and Inactivation Mechanisms

Human norovirus (HuNoV) is an important cause of acute gastroenteritis and can be transmitted by water exposures, but its persistence in water is not well understood. Loss of HuNoV infectivity in surface water was compared with persistence of intact HuNoV capsids and genome segments. Surface water from a freshwater creek was filter-sterilized, inoculated with HuNoV (GII.4) purified from stool, and incubated at 15 or 20 °C. We measured HuNoV infectivity via the human intestinal enteroid system and HuNoV persistence via reverse transcription-quantitative polymerase chain reaction assays without (genome segment persistence) or with (intact viral capsid persistence) enzymatic pretreatment to digest naked RNA. For infectious HuNoV, results ranged from no significant decay to a decay rate constant ("k") of 2.2 day^-1. In one creek water sample, genome damage was likely a dominant inactivation mechanism. In other samples from the same creek, loss of HuNoV infectivity could not be attributed to genome damage or capsid cleavage. The range in k and the difference in the inactivation mechanism observed in water from the same site could not be explained, but variable constituents in the environmental matrix could have contributed. Thus, a single k may be insufficient for modeling virus inactivation in surface waters.

Viable Norovirus Persistence in Water Microcosms

Human noroviruses are one of the leading causes of acute gastroenteritis worldwide. Based on quantitative microbial risk assessments, norovirus contributes the greatest infectious risk of any pathogen from exposure to sewage-contaminated water; however, these estimates have been based upon molecular (i.e., RNA-based) data as human norovirus has remained largely unculturable in the laboratory. Current approaches to assess the environmental fate of noroviruses rely on the use of culturable surrogate viruses and molecular methods. Human intestinal enteroids (HIEs) are an emerging cell culture system capable of amplifying viable norovirus. Here, we applied the HIE assay to assess both viable norovirus and norovirus RNA persistence in surface, tap, and deionized water microcosms. Viable norovirus decreased to below the detection limit in tap and deionized water microcosms and was measured in a single replicate in the surface water microcosm at study conclusion (28 days). Conversely, the norovirus RNA signal remained constant over the duration of the study, even when viable norovirus was below the limit of detection. Our findings demonstrate the disconnect between current environmental norovirus detection via molecular methods and viability as assessed through the HIE assay. These results imply that molecular norovirus monitoring is not inherently representative of infectious norovirus.