Brote de gastroenteritis por Norovirus causado por el consumo de agua de suministro público

Two successive outbreaks of acute gastroenteritis due to norovirus GII.6 in a holiday camp house

When two outbreaks occur in the same institution within a short period of time, an important health and social concern is generated. Two gastroenteritis outbreaks occurring a week apart in the same facility were reported in Lleida, Spain, in 2018. The objective of this study was to describe the clinical, epidemiological and microbiological investigation carried out and to determine the risk factors. Demographic data, food consumption and symptoms were collected. Health inspections of the facility were carried out. Risk ratio and their 95% confidence intervals were estimated for the implication of each food consumed. The attack rate was 89.7% in the first outbreak and 69.6% in the second outbreak. The most frequent symptoms in the first and second outbreak were abdominal pain (88.5% and 100%, respectively), vomiting (80.8% and 87.5%, respectively) and nausea (69.2% and 81.3%, respectively). The first outbreak was associated with the consumption of a salad and the second with a cheese omelet. Norovirus GII.6 was detected by RT-PCR and sequenced in both groups of students and in the food handlers who prepared the meals. These results highlight the importance of exclusion from work of food handlers with gastroenteritis, the adequate availability of mechanisms for correct hand washing and the correct cleaning of surfaces.

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.

A Waterborne Gastroenteritis Outbreak Caused by a GII Norovirus in a Holiday Camp in Catalonia (Spain), 2017

On 2 February 2017, Epidemiological Surveillance Services were notified of an outbreak of acute gastroenteritis (AGE) among schoolchildren who had taken part of a school trip from 30 January to 3 February 2017 at a holiday camp in Catalonia. A retrospective cohort study was performed to identify the causative agent, estimate the magnitude of the outbreak and identify its source, as well as to determine the route of transmission. Data collected by standardised questionnaires identified 41 episodes of AGE among 174 individuals who attended the camp. Cases had mainly symptoms of abdominal pain (73.8%), nausea (64.3%), vomiting (54.8%), diarrhoea (45.2%) and headache (42.9%). Consumption of water was associated with gastroenteritis (crude RR: 1.72, 95%CI: 1.01–2.92; adjusted RR: 1.88, 95%CI 1.03–3.56). NoV GII was detected in faeces (5 out of 13) and water samples. Additionally, faecal indicator bacteria and protozoa were detected in water samples. The outbreak showed a high attack rate and was caused by a natural water fountain not properly treated and not monitored for safety quality. There could have been a discharge of wastewater at a point close to the fountain; however, the source of contamination of the water could not be identified. Health education may be useful to eliminate risks associated with the consumption of untreated water from natural fountains.

Genomic Modeling as an Approach to Identify Surrogates for Use in Experimental Validation of SARS-CoV-2 and HuNoV Inactivation by UV-C Treatment

Severe Acute Respiratory Syndrome coronavirus-2 (SARS-CoV-2) is responsible for the COVID-19 pandemic that continues to pose significant public health concerns. While research to deliver vaccines and antivirals are being pursued, various effective technologies to control its environmental spread are also being targeted. Ultraviolet light (UV-C) technologies are effective against a broad spectrum of microorganisms when used even on large surface areas. In this study, we developed a pyrimidine dinucleotide frequency based genomic model to predict the sensitivity of select enveloped and non-enveloped viruses to UV-C treatments in order to identify potential SARS-CoV-2 and human norovirus surrogates. The results revealed that this model was best fitted using linear regression with r ² = 0.90. The predicted UV-C sensitivity (D ₉₀ - dose for 90% inactivation) for SARS-CoV-2 and MERS-CoV was found to be 21.5 and 28 J/m², respectively (with an estimated 18 J/m² obtained from published experimental data for SARS-CoV-1), suggesting that coronaviruses are highly sensitive to UV-C light compared to other ssRNA viruses used in this modeling study. Murine hepatitis virus (MHV) A59 strain with a D ₉₀ of 21 J/m² close to that of SARS-CoV-2 was identified as a suitable surrogate to validate SARS-CoV-2 inactivation by UV-C treatment. Furthermore, the non-enveloped human noroviruses (HuNoVs), had predicted D ₉₀ values of 69.1, 89, and 77.6 J/m² for genogroups GI, GII, and GIV, respectively. Murine norovirus (MNV-1) of GV with a D ₉₀ = 100 J/m² was identified as a potential conservative surrogate for UV-C inactivation of these HuNoVs. This study provides useful insights for the identification of potential non-pathogenic (to humans) surrogates to understand inactivation kinetics and their use in experimental validation of UV-C disinfection systems. This approach can be used to narrow the number of surrogates used in testing UV-C inactivation of other human and animal ssRNA viral pathogens for experimental validation that can save cost, labor and time.

Safe drinking water and waterborne outbreaks

The present work compiles a review on drinking waterborne outbreaks, with the perspective of production and distribution of microbiologically safe water, during 2000-2014. The outbreaks are categorised in raw water contamination, treatment deficiencies and distribution network failure. The main causes for contamination were: for groundwater, intrusion of animal faeces or wastewater due to heavy rain; in surface water, discharge of wastewater into the water source and increased turbidity and colour; at treatment plants, malfunctioning of the disinfection equipment; and for distribution systems, cross-connections, pipe breaks and wastewater intrusion into the network. Pathogens causing the largest number of affected consumers were Cryptosporidium, norovirus, Giardia, Campylobacter, and rotavirus. The largest number of different pathogens was found for the treatment works and the distribution network. The largest number of affected consumers with gastrointestinal illness was for contamination events from a surface water source, while the largest number of individual events occurred for the distribution network.

Outbreak of acute gastroenteritis caused by contamination of drinking water in a factory, the Basque Country

On 18 September 2013, the Gipuzkoa Epidemiology Unit was notified of an outbreak of acute gastroenteritis (AGE) among employees at a domestic appliance factory. The first signs of the outbreak had emerged at the end of June and at the time of the notification 30 workers were on sick leave for gastroenteritis. Some employees had had more than one episode and the main symptoms were diarrhoea and vomiting. An investigation began to identify the causative agent, assess exposure and determine the route of transmission. Data collected by a questionnaire identified 302 episodes of AGE among 238 people affected between June and September 2013. The source of water consumed was found to be a risk factor associated with the appearance of symptoms both in the crude and the adjusted analysis: odds ratio 1.8 (0.8-4.2) and 6.4 (4.2-9.8), respectively. Microbiological analysis of stool samples and of water confirmed the presence of norovirus and rotavirus. The environmental study detected a connection between an industrial use water system and drinking water at the factory. It was concluded that the outbreak was caused by mixed viral infections, due to contamination of drinking water.

UVC Inactivation of dsDNA and ssRNA Viruses in Water: UV Fluences and a qPCR-Based Approach to Evaluate Decay on Viral Infectivity

Disinfection by low-pressure monochromatic ultraviolet (UVC) radiation (253.7 nm) became an important technique to sanitize drinking water and also wastewater in tertiary treatments. In order to prevent the transmission of waterborne viral diseases, the analysis of the disinfection kinetics and the quantification of infectious viral pathogens and indicators are highly relevant and need to be addressed. The families Adenoviridae and Polyomaviridae comprise human and animal pathogenic viruses that have been also proposed as indicators of fecal contamination in water and as Microbial Source Tracking tools. While it has been previously suggested that dsDNA viruses may be highly resistant to UVC radiation compared to other viruses or bacteria, no information is available on the stability of polyomavirus toward UV irradiation. Here, the inactivation of dsDNA (HAdV2 and JCPyV) and ssRNA (MS2 bacteriophage) viruses was analyzed at increasing UVC fluences. A minor decay of 2-logs was achieved for both infectious JC polyomaviruses (JCPyV) and human adenoviruses 2 (HAdV2) exposed to a UVC fluence of 1,400 J/m(2), while a decay of 4-log was observed for MS2 bacteriophages (ssRNA). The present study reveals the high UVC resistance of dsDNA viruses, and the UV fluences needed to efficiently inactivate JCPyV and HAdV2 are predicted. Furthermore, we show that in conjunction with appropriate mathematical models, qPCR data may be used to accurately estimate virus infectivity.

Norovirus and MS2 inactivation kinetics of UV-A and UV-B with and without TiO2

Germicidal ultraviolet, such as 254-nm UV-C, is a common method of disinfection of pathogenic enteric viruses. However, the disinfection efficacies of UV-A or -B in terms of inactivating waterborne viruses such as norovirus have not been characterized. We evaluated the inactivation kinetics of MS2 bacteriophage and murine norovirus (MNV), a surrogate of human norovirus (NoV), by UV-A and -B. In addition to UV disinfection, we further investigated whether the presence of TiO2 could enhance the virus inactivation kinetics of UV-A and -B. Both MS2 and MNV were highly resistant to UV-A. However, the addition of TiO2 enhanced the efficacy of UV-A for inactivating these viruses. UV-A dose of 1379 mJ/cm(2) resulted in a 4 log10 reduction. In comparison, UV-B alone effectively inactivated both MS2 and MNV, as evidenced by the 4 log10 reduction by 367 mJ/cm(2) of UV-B. The addition of TiO2 increased the inactivation of MS2; however, it did not significantly increase the efficacy of UV-B disinfection for inactivating MNV. When these treatments were applied to field water such as groundwater, the results were generally consistent with the laboratory findings. Our results clearly indicated that UV-B is useful for the disinfection of waterborne norovirus. However, MNV was quite resistant to UV-A, and UV-A effectively inactivated the tested viruses only when used in combination with TiO2.

One year environmental surveillance of rotavirus specie A (RVA) genotypes in circulation after the introduction of the Rotarix® vaccine in Rio de Janeiro, Brazil

Rotavirus specie A (RVA) infection is the leading cause of severe acute diarrhea among young children worldwide. To reduce this major RVA health impact, the Rotarix® vaccine (GlaxoSmithKline, Rixensart, Belgium) was introduced in the Brazilian Expanded Immunization Program in March 2006 and became available to the entire birth cohort. The aim of this study was to evaluate the spread of RVA in the environment after the introduction of Rotarix® in Brazil. For this purpose, a Wastewater Treatment Plant (WTP) in Rio de Janeiro was monitored for one year to detect, characterize and discriminate RVA genotypes and identify possible circulation of vaccine strains. Using TaqMan® quantitative PCR (qPCR), RVA was detected in 100% (mean viral loads from 2.40×10(5) to 1.16×10(7) genome copies (GC)/L) of sewage influent samples and 71% (mean viral loads from 1.35×10(3) to 1.64×10(5)GC/L) of sewage effluent samples. The most prevalent RVA genotypes were P[4], P[6] and G2, based on VP4 and VP7 classification. Direct nucleotide sequencing (NSP4 fragment) and restriction enzyme digestion (NSP3) analysis did not detect RVA vaccine-like strains from the sewage samples. These data on RVA detection, quantification and molecular characterization highlight the importance of environmental monitoring as a tool to study RVA epidemiology in the surrounding human population and may be useful on ongoing vaccine monitoring programs, since sewage may be a good screening option for a rapid and economical overview of the circulating genotypes.

Use of propidium monoazide in reverse transcriptase PCR to distinguish between infectious and noninfectious enteric viruses in water samples

Human enteric viruses can be present in untreated and inadequately treated drinking water. Molecular methods, such as the reverse transcriptase PCR (RT-PCR), can detect viral genomes in a few hours, but they cannot distinguish between infectious and noninfectious viruses. Since only infectious viruses are a public health concern, methods that not only are rapid but also provide information on the infectivity of viruses are of interest. The intercalating dye propidium monoazide (PMA) has been used for distinguishing between viable and nonviable bacteria with DNA genomes, but it has not been used to distinguish between infectious and noninfectious enteric viruses with RNA genomes. In this study, PMA in conjunction with RT-PCR (PMA-RT-PCR) was used to determine the infectivity of enteric RNA viruses in water. Coxsackievirus, poliovirus, echovirus, and Norwalk virus were rendered noninfectious or inactivated by treatment with heat (72 degrees C, 37 degrees C, and 19 degrees C) or hypochlorite. Infectious or native and noninfectious or inactivated viruses were treated with PMA. This was followed by RNA extraction and RT-PCR or quantitative RT-PCR (qRT-PCR) analysis. The PMA-RT-PCR results indicated that PMA treatment did not interfere with detection of infectious or native viruses but prevented detection of noninfectious or inactivated viruses that were rendered noninfectious or inactivated by treatment at 72 degrees C and 37 degrees C and by hypochlorite treatment. However, PMA-RT-PCR was unable to prevent detection of enteroviruses that were rendered noninfectious by treatment at 19 degrees C. After PMA treatment poliovirus that was rendered noninfectious by treatment at 37 degrees C was undetectable by qRT-PCR, but PMA treatment did not affect detection of Norwalk virus. PMA-RT-PCR was also shown to be effective for detecting infectious poliovirus in the presence of noninfectious virus and in an environmental matrix. We concluded that PMA can be used to differentiate between potentially infectious and noninfectious viruses under the conditions defined above.

Why "winter" vomiting disease? Seasonality, hydrology, and Norovirus epidemiology in Toronto, Canada

Norovirus is a common cause of gastroenteritis, and is thought to be the causative agent in 68-90% of all gastroenteritis outbreaks. The seasonality of disease occurrence is sufficiently stereotyped to result in this disease being dubbed "winter vomiting disease." The genesis of this seasonality has been obscure. We sought to identify environmental factors associated with Norovirus outbreaks in Toronto, Canada. We evaluated 253 outbreaks of gastroenteritis linked to Norovirus between November 2005 and March 2008. Poisson regression models were constructed to evaluate associations between average environmental exposures and case counts. A case-crossover approach was used to evaluate associations between acute changes in environment and outbreak risk. Case-crossover analysis indicated an association between low Lake Ontario temperature (<or=4 degrees C) (hazard ratio [HR], 5.61 [95% CI, 2.81-11.12]) and high flow (>2.5 m(3)/s) in the Don River (HR, 3.17 [95% CI, 2.30-4.36]), 1-7 days prior to case occurrence. For both exposure variables, the highest hazard ratios were found 24-48 h prior to case onset. Regression models provided further support for these patterns. The association between local watershed conditions and Norovirus outbreak risk suggest a source-water reservoir for this pathogen. We hypothesize that the reservoir may be maintained through the discharge of wastewater containing virus particles; wintertime seasonality may be explained by enhanced viral persistence at low temperatures.

Inactivation and UV disinfection of murine norovirus with TiO2 under various environmental conditions

We studied inactivation and UV disinfection of murine norovirus (MNV) as a surrogate for human norovirus. We investigated the effects of different surface characteristics, temperatures, and NaCl concentrations on MNV survival using both a plaque assay and a real-time TaqMan reverse transcription (RT)-PCR assay. MNV survived more than 40 days on diaper material, on gauze, and in a stool suspension. Compared to inactivation at lower temperatures (-20 and 4 degrees C), inactivation of MNV was greater at higher temperatures (18 and 30 degrees C). On the surface of both gauze and diaper material, there was a <2-log(10) reduction in the amount of infectious MNV in 40 days after incubation at both -20 and 4 degrees C, compared to a >5-log(10) reduction after incubation at 30 degrees C in 24 days. MNV survived better in a stool suspension than on the surface of gauze or diaper material. A higher salt concentration increased the rate of inactivation of MNV. In 72 h, <0.3-, 1.5-, and 2.5-log(10) reductions in the amount of infectious MNV occurred in distilled water and 0.5 and 1 M NaCl, respectively. We observed only minor reductions in the numbers of viral RNA copies as quantified by real-time TaqMan RT-PCR regardless of the temperature, the salt concentration, or the suspending medium. We also evaluated UV disinfection of infectious MNV with and without TiO(2). The amount of MNV was significantly reduced by 254-nm UV with and without TiO(2). When 25 mJ/cm(2) UV was used, 3.3- and 3.6-log(10) reductions in the amounts of infectious MNV occurred with and without TiO(2), respectively. Our results demonstrate that MNV can persist in various environmental conditions and can be efficiently controlled by UV disinfection.