Norovirus outbreaks from drinking water

Contamination source identification for the prompt management of a gastroenteritis outbreak caused by norovirus in drinking water in Northern Italy

In June 2022, a gastroenteritis outbreak occurred in a town in Northern Italy, possibly associated with the ingestion of norovirus from public drinking water. Noroviruses are highly infectious RNA viruses, with high stability in the environment. They are the primary cause of non-bacterial gastroenteritis worldwide, and despite the fact that the disease is mainly self-limiting, norovirus infection can lead to severe illness in the immunocompromised, the elderly and children. Immediately after the notification of the suspected norovirus outbreak, faecal specimens were collected from hospitalised patients, and water samples were collected from public drinking fountains in the affected area, to confirm the presence of norovirus. Norovirus was detected in 80 % (95 % CI 0.58-0.91) of the faecal specimens, and in 50 % (95 % CI 0.28-0.72) of the water samples using RT (reverse transcription) Real-time PCR. The identification of GII genotype in all samples confirmed public drinking water as the source of norovirus contamination. In addition, in one faeces and one water sample, the co-presence of genotypes GI and GII was detected. The strains were typed by sequencing, with most of them belonging to the genotype GII.3. Immediately after the confirmation of norovirus contamination in public drinking water, the local competent authorities applied safety measures, resulting in a decline in number of cases. Moreover, after the application of disinfection protocols in the water plant, the sampling was repeated with negative results for norovirus in the affected area. However, positive samples were found in the neighbouring area (prevalence 10.00 %, 95 % CI 0.02-0.40) and in the water spring (prevalence 50.00 %, 95 % CI 0.21-0.78), suggesting norovirus persistence and spread from the water source. The prompt identification of the source of contamination, and collaboration with the local authorities guided the implementation of proper procedures to control viral spread, resulting in the successful control of the outbreak.

A systematic review and meta-analysis indicates a high risk of human noroviruses contamination in vegetable worldwide, with GI being the predominant genogroup

Human noroviruses (HuNoVs) are the most predominant viral agents of acute gastroenteritis. Vegetables are important vehicles of HuNoVs transmission. This study aimed to assess the HuNoVs prevalence in vegetables. We searched the Web of Science, Excerpta Medica Database, PubMed, and Cochrane databases until June 1, 2023. A total of 27 studies were included for the meta-analysis. Statistical analysis was conducted using Stata 14.0 software. This analysis showed that the pooled HuNoVs prevalence in vegetables was 7 % (95 % confidence interval (CI): 3-13) worldwide. The continent with largest number of studies was Europe, and the highest number of samples was lettuce. As revealed by the results of the subgroup meta-analysis, the prevalence of GI genogroup was the highest (3 %, 95 % CI: 1-7). A higher prevalence was seen in vegetables from farms (18 %, 95 % CI: 5-37), while only 4 % (95 % CI: 1-8) in retail. The HuNoVs prevalence of ready-to-eat vegetables and non-ready-to-eat vegetables was 2 % (95 % CI: 0-8) and 9 % (95 % CI: 3-16), respectively. The prevalence by quantitative real time RT-PCR was 8 % (95 % CI: 3-15) compared to 3 % (95 % CI: 0-13) by conventional RT-PCR. Furthermore, the HuNoVs prevalence in vegetables was 6 % (95 % CI: 1-14) in ISO pretreatment method and 8 % (95 % CI: 1-19) in non-ISO method, respectively. This study is helpful in comprehensively understanding the prevalence of HuNoVs contamination in vegetables worldwide.

Acute gastroenteritis outbreak associated with multiple and rare norovirus genotypes after storm events in Santa Catarina, Brazil

Norovirus is a major cause of acute diarrheal disease (ADD) outbreaks worldwide. In the present study, we investigated an ADD outbreak caused by norovirus in several municipalities of Santa Catarina state during the summer season, southern Brazil in 2023. As of the 10th epidemiological week of 2023, approximately 87 000 ADD cases were reported, with the capital, Florianópolis, recording the highest number of cases throughout the weeks. By using RT-qPCR and sequencing, we detected 10 different genotypes, from both genogroups (G) I and II. Some rare genotypes were also identified. Additionally, rotavirus and human adenovirus were sporadically detected among the ADD cases. Several features of the outbreak suggest that sewage-contaminated water could played a role in the surge of ADD cases. Storm events in Santa Catarina state that preceded the outbreak likely increased the discharge of contaminated wastewater and stormwater into water bodies, such as rivers and beaches during a high touristic season in the state. Climate change-induced extreme weather events, including intensified rainfall and frequent floods, can disturb healthcare and sanitation systems. Implementing public policies for effective sanitation, particularly during peak times, is crucial to maintain environmental equilibrium and counter marine pollution.

Application of electric field treatment (EFT) for microbial control in water and liquid food

Water disinfection and food pasteurization are critical to reducing waterborne and foodborne diseases, which have been a pressing public health issue globally. Electrified treatment processes are emerging and have become promising alternatives due to the low cost of electricity, independence of chemicals, and low potential to form by-products. Electric field treatment (EFT) is a physical pathogen inactivation approach, which damages cell membrane by irreversible electroporation. EFT has been studied for both water disinfection and food pasteurization. However, no study has systematically connected the two fields with an up-to-date review. In this article, we first provide a comprehensive background of microbial control in water and food, followed by the introduction of EFT. Subsequently, we summarize the recent EFT studies for pathogen inactivation from three aspects, the processing parameters, its efficacy against different pathogens, and the impact of liquid properties on the inactivation performance. We also review the development of novel configurations and materials for EFT devices to address the current challenges of EFT. This review introduces EFT from an engineering perspective and may serve as a bridge to connect the field of environmental engineering and food science.

Norovirus GII.3[P12] Outbreak Associated with the Drinking Water Supply in a Rural Area in Galicia, Spain, 2021

Noroviruses are likely to be underrecognized in most suspected waterborne outbreaks. Therefore, effective norovirus detection and the early recognition of water as a possible source of infection are important to reduce morbidity as appropriate steps are taken to control the source.

An acute gastroenteritis outbreak associated with a contaminated water supply system, Turkey, 2018

Disruption of routine monitorization and chlorination of the water supply system during a week-long holiday led to a multi-organism gastroenteritis outbreak in a district with limited laboratory support. More than a 10-fold increase in patients with gastroenteritis was reported. Enteropathogenic Escherichia coli, Enteroaggregative E. coli, and norovirus were detected in human specimen samples. The main water tank and pipes were rusted; 13 out of the 19 water samples tested positive for total Coliform (1-920 colony-forming units (CFU)/100 ml) and E. coli (1-720 CFU/100 ml). Chlorine levels were below 0.2 ppm in seven of the nine samples. Information of 1,815 cases was obtained from the hospital records with a crude attack rate of 2.9%. Cases widespread in the district increased throughout the holiday, epidemic curve revealed a point-source outbreak. The case-control study revealed that consumption of drinking tap water and using it to clean vegetables/fruits were significantly associated with the illness. While drinking only bottled water had a protective effect against the illness. The culture technique showed that the water supply samples were positive for pathogenic bacteria. Upon decision in a multi-stakeholder meeting, the water tank was cleaned, and the Municipality initiated the renovation of the water supply system.

High Prevalence and Diversity of Caliciviruses in a Community Setting Determined by a Metagenomic Approach

We recently carried out a metagenomic study to determine the fecal virome of infants during their first year of life in a semirural community in Mexico. A total of 97 stool samples from nine children were collected starting 2 weeks after birth and monthly thereafter until 12 months of age. In this work, we describe the prevalence and incidence of caliciviruses in this birth cohort. We found that 54 (56%) and 24 (25%) of the samples were positive for norovirus and sapovirus sequence reads detected by next-generation sequencing, respectively. Potential infections were arbitrarily considered when at least 20% of the complete virus genome was determined. Considering only these samples, there were 3 cases per child/year for norovirus and 0.33 cases per child/year for sapovirus. All nine children had sequence reads related to norovirus in at least 2 and up to 10 samples, and 8 children excreted sapovirus sequence reads in 1 and up to 5 samples during the study. The virus in 35 samples could be genotyped. The results showed a high diversity of both norovirus (GI.3[P13], GI.5, GII.4, GII.4[P16], GII.7[P7], and GII.17[P17]) and sapovirus (GI.1, GI.7, and GII.4) in the community. Of interest, despite the frequent detection of caliciviruses in the stools, all children remained asymptomatic during the study. Our results clearly show that metagenomic studies in stools may reveal a detailed picture of the prevalence and diversity of gastrointestinal viruses in the human gut during the first year of life.

IMPORTANCE Human caliciviruses are important etiological agents of acute gastroenteritis in children under 5 years of age. Several studies have characterized their association with childhood diarrhea and their presence in nondiarrheal stool samples. In this work, we used a next-generation sequencing approach to determine, in a longitudinal study, the fecal virome of infants during their first year of life. Using this method, we found that caliciviruses can be detected significantly more frequently than previously reported, providing a more detailed picture of the prevalence and genetic diversity of these viruses in the human gut during early life.

Illuminating Human Norovirus: A Perspective on Disinfection of Water and Surfaces Using UVC, Norovirus Model Organisms, and Radiation Safety Considerations

Human noroviruses (HuNoVs) are a major cause of gastroenteritis and are associated with high morbidity because of their ability to survive in the environment and small inoculum size required for infection. Norovirus is transmitted through water, food, high touch-surfaces, and human-to-human contact. Ultraviolet Subtype C (UVC) light-emitting diodes (LEDs) can disrupt the norovirus transmission chain for water, food, and surfaces. Here, we illuminate considerations to be adhered to when picking norovirus surrogates for disinfection studies and shine light on effective use of UVC for norovirus infection control in water and air and validation for such systems and explore the blind spot of radiation safety considerations when using UVC disinfection strategies. This perspective also discusses the promise of UVC for norovirus mitigation to save and ease life.

Determination of murine norovirus aerosol concentration during toilet flushing

Murine norovirus (MNV) was used as a surrogate for human viral pathogens (e.g., norovirus) to determine if toilet flushing resulted in the aerosolization of virus. A flushometer type toilet was seeded with a viral solution of 105 and 106 PFU mL-1 of MNV and then flushed. Upon flushing, two bioaerosol samplers were activated to collect aerosolized MNV. Prior to the experiment, two optical particle counters monitored particle size and number distribution of aerosol produced from flushing a toilet across height, position, and side. The location with the highest mean particle concentration, was behind the toilet and 0.15 m above the toilet bowl rim, which is where bioaerosol sampling occurred. Bioaerosol and toilet water samples were collected, extracted and then quantified using RT-ddPCR. The concentration of MNV collected after seeding the toilet water ranged from 2.18 × 105 to 9.65 × 106 total copies of MNV. Positive samples of airborne MNV were detected with collected concentrations ranging from 383 to 684 RNA copies/m3 of air. This study provides evidence that viral pathogens may be aerosolized when a toilet is flushed. Furthermore, the MNV used in this study is a model organism for human norovirus and may be generalizable to other viral pathogens (e.g., coronavirus). This study suggests that virus is aerosolized from toilet flushing and may contribute to human exposure to viral pathogens.

Genomic detection of waterborne enteric viruses as water quality indicators in Al-Zarqa River, Jordan

Al-Zarqa River is the second main tributary to River Jordan after the Yarmouk River. The river flow has been modified by discharge of industrial wastewater and treated domestic water. Concerns about the occurrence of waterborne pathogenic viruses in the surface waters of Al-Zarqa River prompted the analysis of the surface water quality with respect to the presence of enteric viruses. Viruses were concentrated from a total of 33 different water environmental samples including raw sewage, effluent samples and river water collected from and around the river over a period of 11 months. Calculated recovery yields for these concentration methods ranged between 2 and 8%. Polymerase chain reaction (PCR), reverse transcriptase-PCR (RT-PCR), nested RT-PCR and southern blotting hybridization analysis were used for the detection of hepatitis A virus, norovirus, astrovirus and human adenovirus 40/41, with the later one being detected in 21 (64%) of the samples that also showed previous positive presence for enteroviruses. To our knowledge, this is the first molecular biology report in Jordan describing the circulation of adenoviruses, which were detected more frequently than enteroviruses in sewage and water samples, and therefore, they can be used as an index for the presence of human pathogenic viruses in water environment.

Risk factors for norovirus infection in healthcare workers during nosocomial outbreaks: a cross-sectional study

Background

Norovirus outbreaks cause severe medico-socio-economic problems affecting healthcare workers and patients. The aim of the study was to investigate prevalence of norovirus infection and risk factors for infection in healthcare workers during nosocomial outbreaks.

Methods

A cross-sectional study of norovirus infections in healthcare workers was performed in seven outbreak wards in a large university hospital. Packs (swab for rectal sampling, and questionnaire) were posted to healthcare workers on notification of a ward outbreak. Rectal samples were examined with norovirus-specific real-time PCR. Replies from questionnaires were analysed using logistic regression models with norovirus genogroup (G)II positive findings as dependent variable. The results are expressed as odds ratios (OR) with 95% confidence intervals (CI). Sequencing and phylogenetic analyses (1040 nucleotides) were used to characterize norovirus strains from healthcare workers. Cluster analyses included norovirus GII.4 strains detected in ward patients during the ongoing outbreaks.

Results

Of 308 packs issued to healthcare workers, 129 (42%) were returned. norovirus GII was detected in 26 healthcare workers (20.2%). Work in cohort care (OR 4.8, 95% CI 1.4–16.3), work in wards for patients with dementia (OR 13.2, 95% CI 1.01–170.7), and having diarrhoea, loose stools or other gastrointestinal symptoms the last week (OR 7.7, 95% CI 2.5–27.2) were associated with increased norovirus prevalence in healthcare workers. Sequencing revealed norovirus GII.4 in healthcare workers samples, and strains detected in healthcare workers and ward patients during a given ward outbreak showed ≥ 99% similarity.

Conclusion

Norovirus positive findings in healthcare workers were strongly associated with symptomatic infection, close contact with sick patients, and dementia nursing.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13756-021-00979-8.

Characteristics of Norovirus Food Poisoning Outbreaks in Korea in the 2000s

ABSTRACT

Norovirus food poisoning outbreaks in Korea (South) appeared in the 2000s and have been increasing since then. We aimed to investigate the epidemiological features of norovirus food poisoning outbreaks in Korea from 2002 to 2017, on the basis of official food poisoning statistics and publically reliable reports, and to find any associations with climate factors. Norovirus was the most common cause of food poisoning among known causative substances in Korea during the study period. More than one-third of the outbreaks occurred in group meal service facilities, including school lunch programs. A few of these facilities used groundwater contaminated with noroviruses to wash or cook food, which contributed to outbreaks. Norovirus occurrences showed strong seasonality: cold and relatively dry winter air may help norovirus to flourish. Both norovirus genotypes GI and GII that are infectious to humans were detected, with GII becoming more prevalent than GI. According to our correlation analysis in connection with climate factors, average temperatures, the highest and lowest temperatures, precipitation, the number of rain days, and humidity showed a significant negative correlation with a monthly norovirus occurrence (P < 0.05). The lowest temperature and average temperature had higher coefficients of correlation, -0.377 and -0.376, respectively. The norovirus outbreaks in Korea showed complex etiological characteristics, although more prevailed in wintertime, and are now a major public health problem. The use of groundwater in group meal service settings is a public health issue, as well as a norovirus concern; therefore, groundwater used in food service facilities and businesses should be treated for safety.

HIGHLIGHTS

Phylogenetic and biological characterizations of a GI.3 norovirus

Noroviruses (NoVs) are a major cause of acute non-bacterial gastroenteritis worldwide. In this study, we report the isolation, near-complete genome sequencing, and expression and biological characterization of the major capsid protein (VP1) of a GI.3 NoV isolated from a child presenting acute gastroenteritis. The genome of the GI.3 NoV is 7746 bp in length, not including the poly-adenylation tail. Phylogenetic analysis based on the complete VP1 nucleotide sequences indicates that GI.3 NoVs could be divided into four clusters, with 4.6%, 5.3%, 6.6%, 1.9% intracluster variations in nucleotide and 4.8%, 3.8%, 6.1%, 1.7% intracluster variations in amino acid sequences, respectively. A Bayesian evolutionary analysis showed that GI.3 NoVs evolved at 2.44 × 10^-3, 2.78 × 10^-3, and 3.04 × 10^-3 nucleotide substitutions/site/year using a strict clock model, an uncorrelated log-normal model (UCLN), and an uncorrelated exponential derivation model (UCED), respectively. VP1 protein expression using a recombinant baculovirus expression system leads to the successful assembly of virus-like particles (VLPs). In vitro VLP-Histo-blood group antigen (HBGA) binding assay indicates that GI.3 NoV VLPs strongly bind to blood type A salivary HBGAs, moderately bind to blood type O salivary HBGAs, and weakly bind or do not bind to blood type B and AB salivary HBGAs. In vitro VLP-HBGA binding blockade assay indicated that the binding of GI.3 NoV VLPs to blood type A salivary HBGAs could only be blocked by anti-GI.3 NoV VLPs serum but not non-GI.3 NoV genotype-specific hyperimmune sera (GI.2, GI.7, GII.4, GII.6, GII.7, and GII.17). The detailed characterization of GI.3 NoV in this study provides evidence that GI.3 NoV undergoes rapid evolution and exhibits no cross-blocking effects, suggesting that GI.3 NoV may potentially be utilized in the development of multivalent NoV vaccines.

Hydrophobic Organic Matter Promotes Coxsackievirus B5 Stabilization and Protection from Heat

In urban rivers, many of which are used for drinking water production, viruses encounter a range of particulate, colloidal, and dissolved organic and inorganic compounds. To date, the impact of environmental organic matter on virus persistence in the environment has received little attention. In the present study, fresh water was fractioned to separate particulate natural organic matter from dissolved forms. Each fraction was tested for its ability to promote coxsackievirus B5 resistance to heat inactivation. Our results demonstrate that, at natural concentrations, environmental waters contain particulate or dissolved compounds that are able to protect viruses from heat. We also show that hydrophobic compounds promote an efficient protection against heat inactivation. This study suggests that local conditions encountered by viruses in the environment could greatly impact their persistence.

Environmental and Adaptive Changes Necessitate a Paradigm Shift for Indicators of Fecal Contamination

Changes in the occurrence, distribution, and seasonal variation of waterborne pathogens due to global climate change may increase the risk of human exposure to these microorganisms, thus heightening the need for more reliable surveillance systems. Routine monitoring of drinking water supplies and recreational waters is performed using fecal indicator microorganisms, such as Escherichia coli , Enterococcus spp., and coliphages. However, the presence and numbers of these indicators, especially E. coli and Enterococcus spp., do not correlate well with those of other pathogens, especially enteric viruses, which are a major cause of waterborne outbreaks associated with contaminated water and food, and recreational use of lakes, ponds, rivers, and estuarine waters. For that reason, there is a growing need for a surveillance system that can detect and quantify viral pathogens directly in water sources to reduce transmission of pathogens associated with fecal transmission. In this review, we present an updated overview of relevant waterborne enteric viruses that we believe should be more commonly screened to better evaluate water quality and to determine the safety of water use and reuse and of epidemiological data on viral outbreaks. We also discuss current methodologies that are available to detect and quantify these viruses in water resources. Finally, we highlight challenges associated with virus monitoring. The information presented in this review is intended to aid in the assessment of human health risks due to contact with water sources, especially since current environmental and adaptive changes may be creating the need for a paradigm shift for indicators of fecal contamination.

Quantitative PCR Detection of Enteric Viruses in Wastewater and Environmental Water Sources by the Lisbon Municipality: A Case Study

Current regulations and legislation require critical revision to determine safety for alternative water sources and water reuse as part of the solution to global water crisis. In order to fulfill those demands, Lisbon municipality decided to start water reuse as part of a sustainable hydric resources management, and there was a need to confirm safety and safeguard for public health for its use in this context. For this purpose, a study was designed that included a total of 88 samples collected from drinking, superficial, underground water, and wastewater at three different treatment stages. Quantitative Polimerase Chain Reaction (PCR) detection (qPCR) of enteric viruses Norovirus (NoV) genogroups I (GI) and II (GII) and Hepatitis A (HepA) was performed, and also FIB (E. coli, enterococci and fecal coliforms) concentrations were assessed. HepA virus was only detected in one untreated influent sample, whereas NoV GI/ NoV GI were detected in untreated wastewater (100/100%), secondary treated effluent (47/73%), and tertiary treated effluent (33/20%). Our study proposes that NoV GI and GII should be further studied to provide the support that they may be suitable indicators for water quality monitoring targeting wastewater treatment efficiency, regardless of the level of treatment.

[On Statistical Underreporting of Norovirus-Infections: Insights from Register Data of Two Local Public Health Authorities]

BACKGROUND

Only laboratory-confirmed norovirus (NoV) cases have to be notified to the Robert Koch Institute (RKI) since 2011, but not other, e. g. clinical-epidemiological cases. It can be assumed that the extent of underreporting of NoV cases in Germany has significantly increased since then.

OBJECTIVES

To discuss the extent of underreporting, we wanted to find out how many laboratory tests were carried out during gastroenteritis outbreaks. Furthermore, the significance of NoV outbreaks in occupational health is discussed.

MATERIALS AND METHODS

Of all pseudonymized gastroenteritis outbreak data reported to 2 local health authorities between 2011 and 2015, the proportion of NoV outbreaks and reported cases of infection among employees in hospitals and community facilities (nursing homes for the elderly, day-care centers, schools) confirmed by laboratory tests was calculated retrospectively.

RESULTS

Only a few gastroenteritis outbreaks in day-care centers were etiologically diagnosed, so that only 6% and less could be classified as NoV outbreaks. In nursing homes for the elderly, about half of the outbreaks were classified as NoV, in hospitals almost all of them. Employees accounted for up to 23% of those affected in NoV outbreaks.

CONCLUSIONS

The low level of laboratory diagnostics carried out during gastroenteritis outbreaks in day-care centers suggests a considerable number of hidden NoV cases. The significant proportion of staff relative to the total number of infected persons during the outbreaks highlights the importance of the burden of NoV outbreaks as a topic in occupational health. Further, large-scale prospective studies are needed to empirically substantiate these initial findings.

Ubiquitous waterborne pathogens

Water is one of the most important substances on earth and without it life cannot exist. However, poor water quality in many parts of the world has increased the number of water-related diseases, making it the leading cause of disease and death globally for both young and old. Waterborne pathogens cause diseases in humans through two major exposure pathways: drinking water and recreational waters. This chapter on waterborne pathogens will be starting with an introduction, followed by descriptions on classical waterborne pathogens; bacteria, viruses, protozoans, and helminths placing emphasis on the World Health Organization guidelines. Further to conventional waterborne pathogens, fresh organisms and new strains from already known pathogens are being identified and that present important additional challenges to both the water and public health sectors. Hence later part of the chapter focuses on the potential waterborne pathogens and will conclude with a summary of the content.

Two Drinking Water Outbreaks Caused by Wastewater Intrusion Including Sapovirus in Finland

Drinking water outbreaks occur worldwide and may be caused by several factors, including raw water contamination, treatment deficiencies, and distribution network failure. This study describes two drinking water outbreaks in Finland in 2016 (outbreak I) and 2018 (outbreak II). Both outbreaks caused approximately 450 illness cases and were due to drinking water pipe breakage and subsequent wastewater intrusion into the distribution system. In both outbreaks, the sapovirus was found in patient samples as the main causative agent. In addition, adenoviruses and Dientamoeba fragilis (outbreak I), and noroviruses, astroviruses, enterotoxigenic and enterohemorragic Escherichia coli (ETEC and EHEC, respectively) and Plesiomonas shigelloides (outbreak II) were detected in patient samples. Water samples were analyzed for the selected pathogens largely based on the results of patient samples. In addition, traditional fecal indicator bacteria and host-specific microbial source tracking (MST) markers (GenBac3 and HF183) were analyzed from water. In drinking water, sapovirus and enteropathogenic E. coli (EPEC) were found in outbreak II. The MST markers proved useful in the detection of contamination and to ensure the success of contaminant removal from the water distribution system. As mitigation actions, boil water advisory, alternative drinking water sources and chlorination were organized to restrict the outbreaks and to clean the contaminated distribution network. This study highlights the emerging role of sapoviruses as a waterborne pathogen and warrants the need for testing of multiple viruses during outbreak investigation.

Data fitting approach more critical than exposure scenarios and treatment of censored data for quantitative microbial risk assessment

Recreational waters are a source of many diseases caused by human viral pathogens, including norovirus genogroup II (NoV GII) and enterovirus (EV). Water samples from the Arenales river in Salta, Argentina, were concentrated by ultrafiltration and analyzed for the concentrations of NoV GII and EV by quantitative PCR. Out of 65 samples, 61 and 59 were non-detects (below the Sample Limit of Detection limit, SLOD) for EV and NoV GII, respectively. We hypothesized that a finite number of environmental samples would lead to different conclusions regarding human health risks based on how data were treated and fitted to existing distribution functions. A quantitative microbial risk assessment (QMRA) was performed and the risk of infection was calculated using: (a) two methodological approaches to find the distributions that best fit the data sets (methods H and R), (b) four different exposure scenarios (primary contact for children and adults and secondary contact by spray inhalation/ingestion and hand-to-mouth contact), and (c) five alternatives for treating censored data. The risk of infection for NoV GII was much higher (and exceeded in most cases the acceptable value established by the USEPA) than for EV (in almost all the scenarios within the recommended limit), mainly due to the low infectious dose of NoV. The type of methodology used to fit the monitoring data was critical for these datasets with numerous non-detects, leading to very different estimates of risk. Method R resulted in higher projected risks than Method H. Regarding the alternatives for treating censored data, replacing non-detects by a unique value like the average or median SLOD to simplify the calculations led to the loss of information about the particular characteristics of each sample. In addition, the average SLOD was highly impacted by extreme values (due to events such as precipitations or point source contamination). Instead, using the SLOD or half- SLOD captured the uniqueness of each sample since they account for the history of the sample including the concentration procedure and the detection method used. Finally, substitution of non-detects by Zero is not realistic since a negative result would be associated with a SLOD that can change by developing more efficient and sensitive methodology; hence this approach would lead to an underestimation of the health risk. Our findings suggest that in most cases the use of the half-SLOD approach is appropriate for QMRA modeling.

The prevalence of non-GII.4 norovirus genotypes in acute gastroenteritis outbreaks in Jinan, China

Noroviruses (NoVs) are the leading cause of acute viral gastroenteritis outbreaks. From June 2015 to March 2017, fifteen outbreaks of acute gastroenteritis (AGE) were reported to the Jinan Center for Disease Control and Prevention in China. To identify the circulating NoV genotypes associated with outbreaks in Jinan, China, 414 specimens from the 15 outbreaks were collected and analyzed for the causative viruses, and phylogenetic analysis was performed on the NoV-positive strains. The NoV detection rate was 57.5% (238/414), and a total of 14 outbreaks were caused by NoVs (eight by infection with genogroup II (GII), five by mixed infection with GI and GII, and one by mixed infection with GII and rotavirus (RoV)-A). A total of 75 NoV sequences were obtained from 13 NoV-positive outbreaks and classified into seven genotypes (38 GII.17, 13 GII.2, 4 GII.3, 4 GII.1, 10 GI.6, 5 GI.5 and 1 GI.3), while GII.4 was not identified. The most prevalent genotype changed yearly during the 2015–2017 period. Phylogenetic analysis demonstrated that these NoV genotypes had high homology with the strains circulating worldwide, especially strains from Asian countries and cities. Our study illustrated that multiple non-GII.4 NoV genotypes were prevalent in outbreaks of AGE in Jinan, China. Year-round surveillance of multiple NoV genotypes could help health authorities reduce the impact of NoV outbreaks on public health.

Application of a salivary immunoassay in a prospective community study of waterborne infections

Quantifying sporadic waterborne infections in community settings can be challenging. Salivary antibody immunoassays are a promising non-invasive tool that can be used in prospective studies of common infections, especially those involving children. This study was conducted in a Massachusetts city, which uses a microbiologically contaminated river as its water source, during summer-early winter periods before and after construction of a new drinking water treatment plant. Monthly saliva samples (7480 samples from 1170 children and 816 adults) were analyzed for immunoglobulin G (IgG) responses to recombinant proteins of Cryptosporidium, one genogroup I (GI) and two GII noroviruses. Immunoconversion was defined as at least four-fold increase in specific antibody responses between two monthly samples with a post-conversion response above a flexible age-dependent cut-off. Episodes of gastroenteritis (diarrhea or vomiting or cramps) were associated with 3.2 (95% confidence limits 1.1; 9.5) adjusted odds ratio (aOR) of immunoconversion to Cryptosporidium; episodes of combined diarrhea and vomiting symptoms were associated with 3.5 (0.8; 15.0) and 4.6 (1.7; 12.6) aORs of an immunoconversion to GI and GII noroviruses, respectively. Swimming in natural water bodies or chlorinated pools was associated with 2.3 (0.4; 15.4) and 4.9 (1.6; 15.5) aORs of immunoconversion to Cryptosporidium, respectively. In a subset of study participants who did not use home water filters, consumption of at least some amount of non-boiled tap water reported in a monthly recall survey was associated with 11.1 (1.2; 100.0) and 0.6 (0.1; 2.5) aORs of immunoconversion to Cryptosporidium before and after the new water treatment plant construction, respectively. Among individuals who used home water filters, associations between non-boiled tap water consumption and Cryptosporidium immunoconversion were not significant before and after new plant construction with aORs of 0.8 (0.2; 3.3) and 0.3 (0.1; 1.6), respectively. The interaction effect of study phase and non-boiled tap water consumption on Cryptosporidium immunoconversions was statistically significant in the entire study population with aOR of 5.4 (1.1; 25.6). This was the first study that has used a salivary antibody immunoassay to demonstrate significant associations between gastrointestinal symptoms and Cryptosporidium and norovirus infections, and between water-related exposures and Cryptosporidium infections.

A gastroenteritis outbreak associated with drinking water in a college in northwest China

An acute gastroenteritis outbreak occurred at a private college in June 2014 in northwest China. This outbreak involved two teachers and 629 students (range: 17-27 years, average 21.3 years). The main symptoms included non-bloody watery diarrhea, stomach ache, nausea, and vomiting, and the duration of illness ranged from 1 to 7 days. Eight of 18 water samples were disqualified. Thirty-four norovirus (NoV) RNA-positive samples were identified from 48 stool-related samples (genotyping results: 13 GII, 13 GI and 8 GI + GII mixture). Fourteen NoV samples were successfully characterized for genotype, including two GII.6, five GI.6, four GI.3, and three GI.1. Enteropathogenic Escherichia coli (EPEC) and enteroadherent Escherichia coli (EAEC) DNA was detected from patient stool specimens and water samples from well one; two EAEC strains and one EPEC strain were isolated from patient stool specimens. The risk ratios (RRs) associated with wells one and two were 1.66 and 1.49, respectively, and the RR associated with living in north dormitory building one was 2.59. The patients' epidemiological characteristics, symptoms, and duration of illness indicated that NoV-contaminated water might be the origin of this outbreak, and RR analysis suggested that the two wells were linked to the outbreak.

Waterborne Norovirus outbreak at a seaside resort likely originating from municipal water distribution system failure

In May 2016 a Norovirus (NoV) gastroenteritis outbreak involved a high school class visiting a seaside resort near Taormina (Mascali, Sicily). Twenty-four students and a teacher were affected and 17 of them showed symptoms on the second day of the journey, while the others got ill within the following 2 days. Symptoms included vomiting, diarrhoea and fever, and 12 students required hospitalisation. Stool samples tested positive for NoV genome by Real-Time polymerase chain reaction assay in all 25 symptomatic subjects. The GII.P2/GII.2 NoV genotype was linked to the outbreak by ORF1/ORF2 sequence analysis. The epidemiological features of the outbreak were consistent with food/waterborne followed by person-to-person and/or vomit transmission. Food consumed at a shared lunch on the first day of the trip was associated to illness and drinking un-bottled tap water was also considered as a risk factor. The analysis of water samples revealed the presence of bacterial indicators of faecal contamination in the water used in the resort as well as in other areas of the municipal water network, linking the NoV gastroenteritis outbreak to tap water pollution from sewage leakage. From a single water sample, an amplicon whose sequence corresponded to the capsid genotype recovered from patients could be obtained.

Pepper mild mottle virus as a process indicator at drinking water treatment plants employing coagulation-sedimentation, rapid sand filtration, ozonation, and biological activated carbon treatments in Japan

To assess the potential of pepper mild mottle virus (PMMoV) as a viral process indicator, its reduction through coagulation-sedimentation (CS) and rapid sand filtration (RSF) were compared with those of Escherichia coli, previously used viral indicators, and norovirus genotype II (NoV GII; enteric virus reference pathogen) in a bench-scale experiment. PMMoV log₁₀ reductions in CS (1.96 ± 0.30) and RSF (0.26 ± 0.38) were similar to those of NoV GII (1.86 ± 0.61 and 0.28 ± 0.46). PMMoV, the most abundant viruses in the raw water, was also determined during CS, RSF, and advanced treatment processes at two full-scale drinking water treatment plants under strict turbidity management over a 13-month period. PMMoV was concentrated from large-volume water samples (10-614 L) and quantified by Taqman-based quantitative polymerase chain reaction. The PMMoV log₁₀ reduction in CS (2.38 ± 0.74, n = 13 and 2.63 ± 0.76, n = 10 each for Plant A and B) and in ozonation (1.91 ± 1.18, n = 5, Plant A) greatly contributed to the overall log₁₀ reduction. Our results suggest that PMMoV can act as a useful treatment process indicator of enteric viruses and can be used to monitor the log₁₀ reduction of individual treatment processes at drinking water treatment plants due to its high and consistent copy numbers in source water.

Detection of waterborne norovirus genogroup I strains using an improved real time RT-PCR assay

Noroviruses (NoVs) are the major global source of acute gastroenteritis (AGE) outbreaks. To detect NoVs, real-time reverse transcription-quantitative PCR (RT-qPCR) assays have been widely employed since the first decade of the 21^st century. We developed a redesigned probe, JJV1PM, for RT-qPCR assay detection of NoV genogroup (G) I strains. The new RT-qPCR assay using the JJV1PM-probe showed broader strain reactivity for 10 NoV GI genotypes, while the old method, using the JJV1PT-probe assay, detected only 7 NoV GI genotypes in a validation panel using human fecal specimens. The improved RT-qPCR assay was also successfully applied to water samples. The JJV1PM-probe assay identified 7 NoV GI genotypes, whereas the JJV1PT-probe assay detected only 2 NoV GI genotypes from water samples. Notably, groundwater-borne NoV GI strains detected by the improved JJV1PM-probe assay were associated with groundwater-borne AGE outbreaks in South Korea. The results of this study underscore the importance of the evaluation of RT-qPCR assays using recently circulating NoV strains prior to field application.

Comparison of Risk Predicted by Multiple Norovirus Dose-Response Models and Implications for Quantitative Microbial Risk Assessment

The application of quantitative microbial risk assessments (QMRAs) to understand and mitigate risks associated with norovirus is increasingly common as there is a high frequency of outbreaks worldwide. A key component of QMRA is the dose-response analysis, which is the mathematical characterization of the association between dose and outcome. For Norovirus, multiple dose-response models are available that assume either a disaggregated or an aggregated intake dose. This work reviewed the dose-response models currently used in QMRA, and compared predicted risks from waterborne exposures (recreational and drinking) using all available dose-response models. The results found that the majority of published QMRAs of norovirus use the ₁ F₁ hypergeometric dose-response model with α = 0.04, β = 0.055. This dose-response model predicted relatively high risk estimates compared to other dose-response models for doses in the range of 1-1,000 genomic equivalent copies. The difference in predicted risk among dose-response models was largest for small doses, which has implications for drinking water QMRAs where the concentration of norovirus is low. Based on the review, a set of best practices was proposed to encourage the careful consideration and reporting of important assumptions in the selection and use of dose-response models in QMRA of norovirus. Finally, in the absence of one best norovirus dose-response model, multiple models should be used to provide a range of predicted outcomes for probability of infection.

An outbreak of norovirus GI-6 infection following a wedding in North West England

In August 2015 a gastroenteritis outbreak occurred following a wedding. An outbreak investigation was undertaken and a cohort study was conducted using an online survey. Of 140 guests, 134 received the survey and 113 responded (84·3% response rate). Seventy respondents met the case definition of vomiting and/or diarrhoea within 72 h of the wedding (61·9% attack rate). Fifteen exposures were associated with illness; on stratification, all were confounded by the ham hock starter. Multivariable analysis showed a significant association with exposure to ham hock (risk ratio 6·62, 95% confidence interval 2·19-20·03). Eight guests and two catering staff submitted stool samples. All tested positive for norovirus GI-6 infection, including a food handler who had vomiting less than 48 h before the wedding. A single genotype was detected among all samples, suggesting a single source of contamination. The transmission pattern suggested point-source exposure. The most plausible cause of the outbreak was transmission from an infected food handler via contaminated food. This highlights the importance of appropriate exclusions for symptomatic food handlers. Additionally, the food handler's stool sample was submitted 7 days after symptom resolution. The potential for extended viral excretion, and the extremely low infective dose of norovirus, may mean that current exclusion guidelines are not of sufficient duration.

Norovirus genotype distribution in outbreaks of acute gastroenteritis among children and older people: an 8-year study

Background

Noroviruses (NoVs) are the most frequent cause of acute gastroenteritis worldwide among people of all ages and the leading cause of gastrointestinal disease outbreaks in various settings. To clarify the differences in epidemic situations among different settings, we investigated epidemiological trends and the distribution of NoV genotypes in Yokohama, Japan.

Methods

Between September 2007 and August 2015, 746 outbreaks of NoV gastroenteritis were reported in kindergarten/nursery schools (K/Ns), primary schools (PSs), and nursing homes for the aged (NHs). Stool samples were collected for NoV testing, and the NoV gene was amplified and sequenced to determine the genotype.

Results

During the eight seasons, 248 NoV outbreaks occurred in K/Ns, 274 outbreaks in PSs, and 224 outbreaks in NHs. These outbreaks occurred throughout the year, except in August, and the number increased in November and peaked in December. The number of outbreaks that occurred from November to February comprised 76.8 % of all outbreaks. The outbreaks originated in K/Ns or PSs in every season, except for one season. Five genogroup (G)I and nine GII genotypes in K/Ns, six GI and 10 GII genotypes in PSs, and three GI and six GII genotypes in NHs were detected during the eight seasons. GII.4 was the most prevalent genotype in K/Ns and NHs. However, GII.6 was the most prevalent genotype in PSs. The epidemic genotypes in K/Ns and PSs changed by NoV season, although GII.4 was always predominant in NHs. Moreover, the distribution of genotypes was significantly different between epidemic and non-epidemic periods in each facility (p < 0.01 for all).

Conclusions

The epidemic situation of NoV outbreaks differs by facility, NoV season, and month. The genotype distribution is likely dependent on the facility and is significantly different between epidemic and non-epidemic periods.

Distribution of Human Norovirus in the Coastal Waters of South Korea

The presence of human norovirus in the aquatic environment can cause outbreaks related to recreational activities and the consumption of norovirus-contaminated clams. In this study, we investigated the prevalence of norovirus genogroups I (GI) and II (GII) in the coastal aquatic environment in South Korea (March 2014 to February 2015). A total of 504 water samples were collected periodically from four coastal areas (total sites = 63), of which 44 sites were in estuaries (clam fisheries) and 19 were in inflow streams. RT-PCR analysis targeting ORF2 region C revealed that 20.6% of the water samples were contaminated by GI (13.3%) or GII (16.6%). The prevalence of human norovirus was higher in winter/spring than in summer/fall, and higher in inflow streams (50.0%) than in estuaries (7.9%). A total of 229 human norovirus sequences were identified from the water samples, and phylogenetic analysis showed that the sequences clustered into eight GI genotypes (GI.1, 2, 3, 4, 5, 6, 7, and 9) and nine GII genotypes (GII.2, 3, 4, 5, 6, 11, 13, 17, and 21). This study highlighted three issues: 1) a strong correlation between norovirus contamination via inflow streams and coastal areas used in clam fisheries; 2) increased prevalence of certain non-GII.4 genotypes, exceeding that of the GII.4 pandemic variants; 3) seasonal shifts in the dominant genotypes of both GI and GII.

A Waterborne Gastroenteritis Outbreak Caused by Norovirus GII.17 in a Hotel, Hebei, China, December 2014

Norovirus (NoV) is responsible for an estimated 90 % of all epidemic nonbacterial outbreaks of gastroenteritis worldwide. Waterborne outbreaks of NoV are commonly reported. A novel GII.17 NoV strain emerged as a major cause of gastroenteritis outbreaks in China during the winter of 2014/2015. During this time, an outbreak of gastroenteritis occurred at a hotel in a ski park in Hebei Province, China. Epidemiological investigations indicated that one water well, which had only recently been in use, was the probable source. GII.17 NoV was detected by real-time reverse-transcription polymerase chain reaction from samples taken from cases, from concentrated water samples from water well, and from the nearby sewage settling tank. Nucleotide sequences of NoV extracted from clinical and water specimens were genetically identical and had 99 % homology with Beijing/CHN/2015. All epidemiological data indicated that GII.17 NoV was responsible for this outbreak. This is the first reported laboratory-confirmed waterborne outbreak caused by GII.17 NoV genotype in China. Strengthening management of well drinking water and systematica monitoring of NoV is essential for preventing future outbreaks.

Polythiophene nanofilms for sensitive fluorescence detection of viruses in drinking water

Molecular imprints of the tobacco necrosis virus (TNV) have been formed within polythiophene nanofilms with an approximate thickness of 200nm. These films have been electrochemically deposited onto conducting Au surfaces. Upon rebinding, the TNV-polythiophene complex changes the fluorescence intensity of the nanofilm. The fluorescence intensity at 410nm was observed to be proportional to the concentration of viruses in the range of 0.1-10ngL(-1) (0.15-15pg) with the lower calculated detection limit of 2.29ngL(-1) (3.4pg). The intensity of the fluorescence emission is not affected by the thickness of the polythiophene film and the nature of TNV specific binding sites. Kinetic data analyses showed that the nanofilm responds to TNV within 2min; and cross-selectivity studies with tobacco mosaic virus (TMV) showed an excellent specificity for the targeted TNV. These binding experiments demonstrate the potential of fluorescence emission for the specific, label free and rapid detection of viruses using nanofilm sensors. Taking into account the lower limit of detection, the fluorescence sensing reported here is reliable, simple to perform, rapid, cost-effective and offers a sensitive analytical method for virus detection in water resources.

The effect of chlorine and combined chlorine/UV treatment on coliphages in drinking water disinfection

Chlorine disinfection is a globally used method to ensure the safety of drinking water. However, it has not always been successful against viruses and, therefore, it is important to find new methods to disinfect water. Seventeen different coliphages were isolated from the treated municipal wastewater. These coliphages and MS2 were treated with different dosages of chlorine in drinking water, and a combined chlorine/ultraviolet irradiation treatment for the chlorine-resistant coliphages. Chlorine disinfection with 0.3-0.5 mg/L total chlorine (free Cl-dosage 0.12-0.21 mg/L) for 10 min achieved 2.5-5.7 Log10-reductions for 11 sensitive coliphages. The six most resistant coliphages showed no reduction with these chlorine concentrations. MS2 was intermediate in chlorine resistance, and thus it is not a good indicator for viruses in chlorine disinfection. In the combined treatment total chlorine of 0.05-0.25 mg/L (free Cl-dosage 0.02-0.08 mg/L) and ultraviolet irradiation (14-22 mWs/cm(2)) were more effective than chlorine alone, and 3-5 Log10-reductions were achieved for the chlorine-resistant strains. The chlorination efficiency could be increased by higher dosages and longer contact times, but this could increase the formation of disinfection by-products. Therefore, the combination treatment is a recommended disinfection method.

Drinking and recreational water-related diseases: a bibliometric analysis (1980-2015)

BACKGROUND

Water - related diseases are worldwide health concern. Microbial contamination and contaminant products in water are a source of disease outbreaks and development of cumulative toxic effects. Ensuring safe water is one of the goals to be achieved at the global level. The aim of this study was to assess publications on drinking and recreational water from a health point of view to understand current problems and future research trends in this field.

METHODS

Scopus, the largest scientific electronic database, was used to retrieve related articles and present the results as bibliometric tables and maps. Search query was modified manually using related terms to maximize accuracy.

RESULTS

A total of 2267 publications were retrieved with an average of 16.82 citations per article. The h-index of retrieved articles was 88. Visual mapping showed that E. coli, diarrhea, cryptosporidiosis, fluoride, arsenic, cancer, chlorine, trihalomethane, and H. pylori were most frequently encountered terms in title and abstract of retrieved articles. The number of articles on water microbiology was a significant (P < 0.01) predictor of worldwide productivity of water - related disease publications. Journal of Water and Health ranked first in number of publications with 136 (6.00 %) articles. The United States of America ranked first in productivity with a total of 623 (27.48 %) articles. Germany (15.44 %), India (16.00 %) and China (20.66 %) had the least international collaboration in water-related disease research. Environmental Protection Agency and Centers for Disease Prevention and Control were among top ten productive institutions. In the top ten cited articles, there were three articles about arsenic, one about aluminum, one about trihalomethane, one about nitrate, one about toxoplasmosis, one about gastroenteritis, and the remaining two articles were general ones.

CONCLUSIONS

There was a linear increase in the number of publications on water - related diseases in the last decade. Arsenic, in drinking water is a serious concern. Cryptosporidiosis and other infectious gastroenteritis remain a major health risk of exposure to contaminated water. Increased number of publications from Asian countries was not associated with a high percentage of international collaboration.

Variability in the recovery of a virus concentration procedure in water: Implications for QMRA

Methods for analysing water for viruses are known to have variable and relatively poor recovery efficiencies. Quantitative method recovery data are needed to correct virus enumeration results so that estimates of virus concentrations in surface waters for QMRA are not too low. Obtaining quantitative data representing method recoveries for different pathogenic viruses is a significant challenge. In this study, we investigated the use of mengovirus process control data for quantifying recovery efficiency of human adenovirus (AdV) and noroviruses GI (NoVGI) and GII (NoVGII) from surface waters. Samples were collected from the inlet to a drinking water treatment plant on the Glomma River, Norway. Performance of the sample concentration procedure was quantified by comparing the virus concentrations found in concentrated and unconcentrated samples. The mean recovery of viruses (1.2%, 0.31%, 0.15% and 0.053% for mengovirus (n = 86), AdV (n = 20), NoVGI (n = 33) and NoVGII (n = 21) respectively) estimated in this study were lower than expected, and the between sample variability in estimated recovery was very high, spanning around 6 orders of magnitude for mengovirus. Within-sample correlation between the estimated recovery of mengovirus and human viruses was poor, and therefore sample specific mengovirus data could not be used to correct all human virus concentrations. Instead beta distributions were fitted to human virus-specific recovery estimates. The magnitude and variability of virus concentration when corrected for the variable recovery efficiency was orders of magnitude higher than the uncorrected concentration. Better estimates of virus concentration could be achieved if a sample-specific spiking control could be developed that mimicked closely the behaviour of human viruses in environmental samples.

Three gastroenteritis outbreaks in South Korea caused by the consumption of kimchi tainted by norovirus GI.4

BACKGROUND

In April 2013, outbreaks of acute gastroenteritis were reported at three schools in Jeonju, South Korea. Epidemiological investigations were performed to characterize the outbreaks and implement appropriate control measures.

MATERIALS AND METHODS

Retrospective cohort studies were performed at these schools. Stool and environmental samples were collected for bacterial and viral assessment. A food supplier of the schools, food company X, was inspected, and samples of cabbage kimchi and groundwater were tested for norovirus by real-time reverse-transcriptase polymerase chain reaction. The relatedness of the detected norovirus strains was evaluated by phylogenetic analysis.

RESULTS

Of the 3347 questionnaires distributed, 631 (attack rate: 18.9%) met the case definition. Among the consumed food items, kimchi products (i.e., cabbage and fresh kimchi) were significantly associated with illness. The kimchi products were supplied by food company X. Among stool samples from 95 students and 34 food handlers at the 3 schools, 39 (41.1%) and 14 (41.2%) samples, respectively, were positive for norovirus. The samples of groundwater and cabbage kimchi at food company X were positive for norovirus. The predominant genotype of norovirus detected in the patient, groundwater, and cabbage kimchi samples, GI.4, shared high nucleotide identity.

CONCLUSIONS

Kimchi products tainted with norovirus GI.4 from contaminated groundwater were linked to the acute gastroenteritis outbreaks. Therefore, kimchi manufacturers in South Korea should apply chlorine disinfection when using groundwater. Moreover, more stringent sanitation requirements and strict regulations for food companies are recommended.

Human Norovirus prevalence in Africa: a review of studies from 1990 to 2013

OBJECTIVES

To assess the contribution of Human Norovirus to diarrhoeal diseases in Africa.

METHODS

We conducted a systematic review of the PubMed and EMBASE databases for published articles of Human Norovirus in Africa between 1990 and 2013. Data were extracted from selected studies and analysed.

RESULTS

A total of 208 eligible studies were identified, of which 55 (from 19 countries) met the inclusion criteria. Many cases were of sporadic gastroenteritis (70.9%) in children (82%), 65.4% of which were seen in an outpatient setting. Over half (59.4%) of the affected children were under 5 years of age. The pooled prevalence rate of Human NoV was 11% (95% CI 8-14%), and the meta-analysis indicated significant heterogeneity between the studies. However, the conditional negative binomial regression could not clearly find the factors affecting the Human NoV prevalence rates reported. A close relationship was found between Human Norovirus strains from environmental and clinical samples.

CONCLUSION

Unreported sporadic gastroenteritis cases of Human Norovirus are common in Africa. Most are community-associated infections. Possible environmental transmission routes have been documented. Combined environmental and clinical studies are required for targeted actions to control transmission of Human Norovirus in Africa. Systematic surveillance of Human Norovirus is needed to measure the burden of Norovirus-induced gastroenteritis in Africa and support any requirements for vaccine development.

Occurrence of Norovirus GII.4 Sydney Variant-related Outbreaks in Korea

Human noroviruses are major causative agents of food and waterborne outbreaks of nonbacterial acute gastroenteritis. In this study, we report the epidemiological features of three outbreak cases of norovirus in Korea, and we describe the clinical symptoms and distribution of the causative genotypes. The incidence rates of the three outbreaks were 16.24% (326/2,007), 4.1% (27/656), and 16.8% (36/214), respectively. The patients in these three outbreaks were affected by acute gastroenteritis. These schools were provided unheated food from the same manufacturing company. Two genotypes (GII.3 and GII.4) of the norovirus were detected in these cases. Among them, major causative strains of GII.4 (Hu-jeju-47-2007KR-like) were identified in patients, food handlers, and groundwater from the manufacturing company of the unheated food. In the GII.4 (Hu-jeju-47-2007KR-like) strain of the norovirus, the nucleotide sequences were identical and identified as the GII.4 Sydney variant. Our data suggests that the combined epidemiological and laboratory results were closely related, and the causative pathogen was the GII.4 Sydney variant strain from contaminated groundwater.

Drinking Water Quality and the Geospatial Distribution of Notified Gastro-Intestinal Infections

INTRODUCTION

Even brief episodes of fecal contamination of drinking water can lead directly to illness in the consumers. In water-borne outbreaks, the connection between poor microbial water quality and disease can be quickly identified. The impact of non-compliant drinking water samples due to E. coli taken for regular monitoring on the incidence of notified acute gastrointestinal infections has not yet been studied.

METHODS

The objective of this study was to analyse the geographical distribution of notified acute gastrointestinal infections (AGI) in Slovenia in 2010, with hotspot identification. The second aim of the study was to correlate the fecal contamination of water supply system on the settlement level with the distribution of notified AGI cases. Spatial analysis using geo-information technology and other methods were used.

RESULTS

Hot spots with the highest proportion of notified AGI cases were mainly identified in areas with small supply zones. The risk for getting AGI was drinking water contaminated with E. coli from supply zones with 50-1000 users: RR was 1.25 and significantly greater than one (p-value less than 0.001).

CONCLUSION

This study showed the correlation between the frequency of notified AGI cases and non-compliant results in drinking water monitoring.

Deciphering the Diversities of Astroviruses and Noroviruses in Wastewater Treatment Plant Effluents by a High-Throughput Sequencing Method

Although clinical epidemiology lists human enteric viruses to be among the primary causes of acute gastroenteritis in the human population, their circulation in the environment remains poorly investigated. These viruses are excreted by the human population into sewers and may be released into rivers through the effluents of wastewater treatment plants (WWTPs). In order to evaluate the viral diversity and loads in WWTP effluents of the Paris, France, urban area, which includes about 9 million inhabitants (approximately 15% of the French population), the seasonal occurrence of astroviruses and noroviruses in 100 WWTP effluent samples was investigated over 1 year. The coupling of these measurements with a high-throughput sequencing approach allowed the specific estimation of the diversity of human astroviruses (human astrovirus genotype 1 [HAstV-1], HAstV-2, HAstV-5, and HAstV-6), 7 genotypes of noroviruses (NoVs) of genogroup I (NoV GI.1 to NoV GI.6 and NoV GI.8), and 16 genotypes of NoVs of genogroup II (NoV GII.1 to NoV GII.7, NoV GII.9, NoV GII.12 to NoV GII.17, NoV GII.20, and NoV GII.21) in effluent samples. Comparison of the viral diversity in WWTP effluents to the viral diversity found by analysis of clinical data obtained throughout France underlined the consistency between the identified genotypes. However, some genotypes were locally present in effluents and were not found in the analysis of the clinical data. These findings could highlight an underestimation of the diversity of enteric viruses circulating in the human population. Consequently, analysis of WWTP effluents could allow the exploration of viral diversity not only in environmental waters but also in a human population linked to a sewerage network in order to better comprehend viral epidemiology and to forecast seasonal outbreaks.

Large scale survey of enteric viruses in river and waste water underlines the health status of the local population

Although enteric viruses constitute a major cause of acute waterborne diseases worldwide, environmental data about occurrence and viral load of enteric viruses in water are not often available. In this study, enteric viruses (i.e., adenovirus, aichivirus, astrovirus, cosavirus, enterovirus, hepatitis A and E viruses, norovirus of genogroups I and II, rotavirus A and salivirus) were monitored in the Seine River and the origin of contamination was untangled. A total of 275 water samples were collected, twice a month for one year, from the river Seine, its tributaries and the major WWTP effluents in the Paris agglomeration. All water samples were negative for hepatitis A and E viruses. AdV, NVGI, NVGII and RV-A were the most prevalent and abundant populations in all water samples. The viral load and the detection frequency increased significantly between the samples collected the most upstream and the most downstream of the Paris urban area. The calculated viral fluxes demonstrated clearly the measurable impact of WWTP effluents on the viral contamination of the Seine River. The viral load was seasonal for almost all enteric viruses, in accordance with the gastroenteritis recordings provided by the French medical authorities. These results implied the existence of a close relationship between the health status of inhabitants and the viral contamination of WWTP effluents and consequently surface water contamination. Subsequently, the regular analysis of wastewater could serve as a proxy for the monitoring of the human viruses circulating in both a population and surface water.

Role of noroviruses as aetiological agents of diarrhoea in developing countries

Diarrhoea is considered to be the second leading cause of death due to infections among children  < 5 years of age worldwide that may be caused by bacteria, parasites, viruses and non-infectious agents. The major causative agents of diarrhoea in developing countries may vary from those in developed countries. Noroviruses are considered to be the most common cause of acute diarrhoea in both children and adults in industrialized countries. On the other hand, there is a lack of comprehensive epidemiological evidence from developing countries that norovirus is a major cause of diarrhoea. In these regions, asymptomatic norovirus infections are very common, and similar detection rates have been observed in patients with diarrhoea and asymptomatic persons. This review summarizes the current knowledge of norovirus infection in developing countries and seeks to position infections with noroviruses among those of other enteropathogens in terms of disease burden in these regions.

Application of salivary antibody immunoassays for the detection of incident infections with Norwalk virus in a group of volunteers

Norovirus infection is the most common cause of acute gastroenteritis in developed countries. Developing an assay based on a non-invasive biomarker for detecting incident norovirus infections could improve disease surveillance and epidemiological investigations. This project involved analysis of IgA and IgG norovirus-specific antibody responses in saliva samples from a Norwalk virus (Genogroup I, genotype 1 norovirus) challenge study involving infected and symptomatic, and non-infected asymptomatic individuals. Saliva was collected at the challenge, and two weeks and 40 days post-challenge. Samples were analyzed using the Luminex fluorometric and Meso Scale Discovery (MSD) electrochemiluminescence immunoassays. Recombinant P domains of Norwalk virus capsid protein, as well as similar recombinant proteins of two genogroup II noroviruses (VA387 and VA207) were used as antigens. Immunoconversions were defined as >4-fold increase in antibody responses to the norovirus antigens. Various sample pre-treatment options, buffers, saliva dilution ratios, and data adjustment approaches to control for sample-to-sample variability in saliva composition were compared using the Luminex assay. The results suggest that adjusting responses to the norovirus antigens for responses to the protein purification tag, glutathione-S-transferase (GST), significantly improved the odds of producing a correct immunoconversion test result. IgG-based tests were more accurate compared to IgA-based tests. At optimal conditions, both Luminex and MSD assays for Norwalk-specific IgG antibodies correctly identified all infected and non-infected individuals. There was no evidence of cross-reactivity of anti-Norwalk virus antibodies with genogroup II noroviruses. These results suggest that salivary antibody responses can be used for the detection of incident infections with Norwalk virus in prospective surveys.

Multiple enteropathogenic viruses in a gastroenteritis outbreak in a military exercise of the Portuguese Army

BACKGROUND

Gastroenteritis is one of the most common infectious diseases in the military populations and can diminish operational effectiveness and impede force readiness.

OBJECTIVES

The present study investigates the cause and the source of an acute gastroenteritis outbreak that occurred during a military exercise of the Portuguese Army, in February 2013.

STUDY DESIGN

A retrospective investigation was performed and stool samples, food items and water were screened for common foodborne bacteria and viruses, namely Norovirus GI, Norovirus GII, Astrovirus, Rotavirus, Adenovirus and Sapovirus.

RESULTS

From the total of 160 soldiers that participated in the military exercise 20 developed gastroenteritis (attack rate of 12.5%). Symptoms were predominantly vomiting (n=17, 85%) and diarrhoea (n=9, 45%). The first cases occurred 24-48h after drinking water from the creek, the plausible origin of the outbreak. The epidemic peak was registered 2 days after and the last cases 6 days after, upon returning to base. No pathogenic bacteria were found in stools however virological analysis revealed the presence of multiple enteropathogenic viruses, namely Norovirus GI (GI.3), Norovirus GII (GII.4 New Orleans 2009), Astrovirus and Sapovirus, as single or co-infections. Food and water samples were not tested for the presence of viruses due to exhaustion of samples on bacteriological analysis.

CONCLUSIONS

To the best of our knowledge this is the first report of a viral gastroenteritis outbreak among military personnel in the Portuguese Army.