Inactivation Of Enteric Viruses Research Articles

Recent Update on UV Disinfection to Fulfill the Disinfection Credit Value for Enteric Viruses in Water.

Ultraviolet (UV) radiation alone or in combination with other oxidation processes is increasingly being considered for water disinfection because of stringent regulatory requirements for pathogen inactivation. To fulfill this requirement, an appropriate UV dose or fluence (mJ/cm2) is applied to combat enteric viruses in surface or treated water. There is a need for a cumulative review on the effectiveness of current and emerging UV technologies against various types of human enteric viruses. We extracted the kinetics data from 52 selected experimental studies on enteric virus inactivation using low pressure (LP-UV), medium pressure (MP-UV), UV-LED, and advanced oxidation processes (AOPs) and applied a simple linear regression analysis to calculate the range of UV fluence (mJ/cm2) needed for 4-log10 inactivation. The inactivation of adenoviruses with LP-UV, MP-UV, and UV/H2O2 (10 mg/L) required the highest fluence, which ranged from 159 to 337, 45, and 115 mJ/cm2, respectively. By contrast, when using LP-UV, the inactivation of other enteric viruses, such as the Caliciviridae and Picornaviridae family and rotavirus, required fluence that ranged from 19 to 69, 18 to 43, and 38 mJ/cm2, respectively. ssRNA viruses exhibit higher sensitivity to UV radiation than dsRNA and DNA viruses. In general, as an upgrade to LP-UV, MP-UV is a more promising strategy for eliminating enteric viruses compared to AOP involving LP-UV with added H2O2 or TiO2. The UV-LED technology showed potential because a lower UV fluence (at 260 and/or 280 nm wavelength) was required for 4-log10 inactivation compared to that of LP-UV for most strains examined in this critical review. However, more studies evaluating the inactivation of enteric viruses by means of UV-LEDs and UV-AOP are needed to ascertain these observations.

Electron Beam Susceptibility of Enteric Viruses and Surrogate Organisms on Fruit, Seed and Spice Matrices

The objective of this study was to use high-energy electron beam (HEEB) treatments to find surrogate microorganisms for enteric viruses and to use the selected surrogates as proof of concept to investigate low-energy electron beam (LEEB) treatments for enteric virus inactivation at industrial scale on frozen blueberries. Six food matrices inoculated with HAV (hepatitis A virus), MNV S99 (murine norovirus), bacteriophages MS2 and Qβ, and Geobacillus stearothermophilus spores were treated with HEEB at 10 MeV using 4, 8 and 16 kGy doses. G. stearothermophilus spores showed the highest inactivation on all matrices except on raisins, with a dose-dependent effect. HAV reached the maximum measurable log10 reduction (> 3.2 log10) when treated at 16 kGy on raisins. MNV showed the highest resistance of all tested microorganisms, independent of the dose, except on frozen blueberries. On frozen blueberries, freeze-dried raspberries, sesame seeds and black peppercorns, HAV showed a mean inactivation level in between those of MS2 and G. stearothermophilus. Based on this, we selected both surrogate organisms as first approximation to estimate HAV inactivation on frozen blueberries during LEEB treatment at 250 keV using 16 kGy. Reductions of 3.1 and 1.3 log10 were measured for G. stearothermophilus spores and MS2, respectively, suggesting that a minimum reduction of 1.4 log10 can be expected for HAV under the same conditions.

Required Chlorination Doses to Fulfill the Credit Value for Disinfection of Enteric Viruses in Water: A Critical Review.

A credit value of virus inactivation has been assigned to the disinfection step in international and domestic guidelines for wastewater reclamation and reuse. To fulfill the credit value for water disinfection, water engineers need to apply an appropriate disinfection strength, expressed as a CT value (mg × min/L), which is a product of disinfectant concentration and contact time, against enteric viruses in wastewater. In the present study, we extracted published experimental data on enteric virus inactivation using free chlorine and monochloramine and applied the Tobit analysis and simple linear regression analysis to calculate the range of CT values (mg × min/L) needed for 4-log10 inactivation. Data were selected from peer-reviewed papers containing kinetics data of virus infectivity and chlorine residual in water. Coxsackie B virus and echovirus require higher CT values (lower susceptibility) for 4-log10 inactivation than adenovirus and a human norovirus surrogate (murine norovirus) with free chlorine. On the other hand, adenovirus has lower susceptibility to monochloramine compared to murine norovirus, coxsackievirus, and echovirus. The factors that influence the required CT value are virus type, pH, water temperature, and water matrix. This systematic review demonstrates that enteroviruses and adenovirus are appropriate representative enteric viruses to evaluate water disinfection using free chlorine and monochloramine, respectively.

UV inactivation of human infectious viruses at two full-scale wastewater treatment plants in Canada

Ultraviolet (UV) disinfection is widely used to inactivate microorganisms prior to release of treated municipal wastewater. However, limited data are available for in situ inactivation of infectious enteric viruses by UV treatment at full-scale. In this study, a total of 51 pre-UV and 50 post-UV samples were collected over a two-year period from two wastewater treatment plants (WWTPs) and analyzed for noroviruses, rotavirus, reovirus, sapovirus, astrovirus, enteroviruses, adenoviruses and JC virus. Both pre-UV and post-UV samples had relatively high concentrations of these viruses determined by qPCR. Infectious viruses were also observed in 98% of pre-UV samples and 76% of post-UV samples by cell culture, using either cytopathic effect (CPE) or integrated cell culture with qPCR (ICC-qPCR). Reovirus was the most common virus detected by ICC-qPCR, present in 92% of pre-UV and 48% of post-UV samples. Infectious enterovirus and adenovirus were detected by ICC-qPCR in 33% and 31% of pre-UV samples, 14% and 20% of post-UV samples, respectively. Mean log10 reduction estimates for infectious reovirus was 1.2 and 1.8 log for the two WWTPs as assessed by ICC-qPCR, which was similar to the reduction of total infectious viruses (1.5 and 1.7 log) as assessed by CPE in cells culture. Overall, quantification of infectious reovirus appears to provide a useful index of enteric virus inactivation during wastewater treatment at full-scale. To our knowledge, this is the first comprehensive study to assess UV inactivation of human enteric viruses at full-scale in WWTPs using both molecular and cell culture techniques, providing important information for quantitative microbial risk assessment of UV inactivation of human viruses in municipal wastewater.

Performance of a storage tank coupled with UV light on enteric virus inactivation in drinking water

Abstract Water destined for personal and household consumption should be safe and acceptable in taste, odor and color. However, complaints about drinking water quality are a common issue among the Brazilian population. Also, due to the pollution of water bodies, social groups that are not supplied by treated water may be exposed to different contaminants. The aim of this study was to assess the efficiency of a water treatment tank coupled with UV light on the inactivation of enteric viruses and the reduction of chlorine concentration for use in residences, as well as in rural and isolated communities. Viral disinfection and chlorine concentration decay assays were performed in a tank with capacity of 300 L and a 36-W UV lamp coupled, with controlled temperature. Recombinant human adenovirus (AdHu5-GFP) and murine norovirus (MNV-1) infectivity were assessed after 0, 3, 6 and 12 h of water recirculation. 99.99% inactivation was reached after 12 h for AdHu5-GFP and before 6 h for MNV-1. Chlorine concentration had a decay of 0.77 mg/L after 12 h. Regarding the efficiency observed, a product model was designed. This tank model was efficient in ensuring viral inactivation as well as in reducing residual chlorine and can be adjusted to other scales.

Evaluation of the Effective Inactivation of Enteric Bacteria and Viruses From Swine Effluent and Sludge at Tropical Temperatures

The safe recycling of organic wastes such as the nutrients obtained from agriculture activities is a relevant aspect of the “One Health” strategy, a worldwide initiative including all aspects of health care for humans and animals, as well as aspects related to the conservation and development of the environment. It represents an important opportunity to mitigate the potential impact of microbial pathogens likely present in nutrient natural sources, as digestate, when applied to land as fertilizers. The objectives of the current study were to determine the inactivation of enteric microorganisms in swine digestate (effluent and sludge) during storage in anaerobic conditions and at different ambient temperatures of tropical zones (16, 22, and 37 °C). Human adenovirus 2 (HAdV-2), bacteriophage PhiX-174, and Salmonella enterica serovar typhimurium (S. typhimurium) were used as enteric microbial models to determine the minimum storage time required to reduce at least 3log of enteric microorganisms load in both matrices at the mentioned temperatures. The minimum storage time required for S. typhimurium was shorter than those observed for viruses at 37 °C, while reduction of at least 3log for S. typhimurium was observed after just 1 day; 20 and 90 days were needed for similar reductions for HAdV-2 and PhiX-174, respectively. Similar results were also observed at lower temperatures: 30 and 45 days were needed for S. typhimurium at 22 and 16 °C, respectively, but 30 and 90 days were needed at 22 °C for HAdV-2 PhiX-174, respectively, or 90 and 120 days at 16 °C for HAdV-2 PhiX-174, respectively. This is a pioneering study on the evaluation of inactivation of enteric viruses in swine digestate in usual tropical ambient temperatures; it demonstrates that the time for a considerable inactivation is longer than that observed for a enteric microorganisms (S. typhimurium), and shows that the storage of swine digestate at the referred temperatures can be used as a low-cost post-treatment to inactivate enteric microorganisms, allowing a further use as safer fertilizer.

Thermal inactivation of MS2 bacteriophage as a surrogate of enteric viruses in cow milk

This study examined the effect of 4 thermal processing methods on inactivation of male-specific bacteriophage MS2 in cow milk. MS2 was used as a viral surrogate of enteric viruses in this inactivation study. Milk samples were spiked at 10, 103, 105, and 107 PFU/ml with a milk fat content of 1.5, 2.5 and 3% weight per volume. We found that with higher milk fat content, survival of MS2 increased in the samples spiked with 105 or 107 PFU/ml, indicating that increasing the milk fat content had a significant effect on the survival of MS2 (p < 0.05) in the thermally processed samples. The inactivation results suggest that the most effective thermal processing for viral inactivation in cow milk was having a high temperature long time (HTLT: 85 °C for 30 min) followed by boiling for 2 min. The least effective thermal processing was low temperature for a long time. Therefore, inactivation of enteric viruses in dairy products with a high level of contamination can be effectively achieved under severe thermal processing such as HTLT, or boiling.

Survival and partitioning of male‐specific coliphage (MS2) as a surrogate for enteric viruses in the production process of traditional butter

AbstractDairy products are potentially considered as important sources of enteric viruses transmission. Currently, there is a lack of appropriate methods for sampling and study of enteric viruses in food products. Therefore, the design of modeling experiments can lead to accurate and precise estimation of viral pathogenic agents. To achieve this aim, the effects of thermal treatment of raw milk, traditional butter storage time, and the bacteriophage spiked levels on survival of the male‐specific MS2 coliphage in traditional butter were studied. MS2 spiking concentrations in three levels of 102, 104, and 106 pfu/ml, traditional butter storage time in four levels (after 1, 2, 3, and 4 weeks), and pasteurization process (85°C for 30 min) of raw milk were chosen as treatments. MS2 coliphage survival, as well as chemical and microbial tests were conducted on pasteurized and unpasteurized butter. The results revealed that pasteurization of raw milk used in the production process of traditional butter led to the reduction of MS2 coliphage survival. Also, acidity and pH affected MS2 bacteriophage recovery in a way that increase in acidity and reduction of pH caused a decrease in bacteriophage recovery. pH was measured at 1‐week intervals until 4 weeks of storage; the highest pH was indicated in the butter samples after the first week, and the lowest pH was observed in the Doogh samples after the fourth week. Therefore, we ascribed the lowest and highest MS2 recovery rates to butter and Doogh, respectively.Practical applicationsTraditional dairy products, including traditional butter and Doogh, are gaining economic and nutritional significance in Iran and worldwide. Little research has been conducted on the survival of enteric viruses in traditional dairy products. However, Safety evaluation of these products is essential as enteric viruses can cause severe health issues in consumers. The results from this study demonstrate that pasteurization could serve as a promising treatment for inactivation of enteric viruses in traditional Iranian butter and Doogh. Additionally, such a treatment might potentially be used to control viral propagation in other dairy products.

The survival and inactivation of enteric viruses on soft surfaces: A systematic review of the literature.

Worldwide, enteric viruses are the main cause of acute gastroenteritis. In humans, these viruses spread via person-to-person contact, food, water, and/or the environment. Their survival and inactivation on hard surfaces have been extensively studied; however, nonlaunderable soft surfaces, such as upholstery and carpet, have received little attention. The aim of this systematic review was to determine factors that influence the survival and inactivation of enteric viruses on nonlaunderable soft surfaces. EBSCO and Web of Science were searched for experimental studies published between 1965 and 2015 using Preferred Reporting Items for Systematic Reviews and Meta-Analyses methods. Titles and abstracts were screened using 3 eligibility criteria. The quality of all study methods was also assessed. Our search yielded 12 articles. Viruses survived between 0 hours and 140 days depending on surface and environment conditions. Virus survival was influenced by temperature, relative humidity, organic content, and deposition method. A variety of chemistries were tested across studies and were shown to have a varied effect on enteric viruses. Chlorine, glutaraldehyde, vaporous ozone, and hydrogen peroxide were the most efficacious against enteric viruses (> 3-log reduction). Environmental factors, such as temperature and relative humidity, can influence survival of enteric viruses on nonlaunderable soft surfaces. The efficacy of liquid and vaporous chemistries are associated with surface and virus type.

Evaluation of Natural Compounds of Plant Origin for Inactivation of Enteric Viruses.

Essential oils (EOs) and some of their main compounds have demonstrated extensive antimicrobial activity in a wide range of food spoilage or pathogenic fungi, yeast and bacteria. The aim of this study was to assess the antiviral activity of Zataria multiflora Boiss. (zataria) and Origanum vulgare (oregano) EOs on hepatitis A virus (HAV) and the effect of thymol, an active compound of Thymus vulgaris and oregano, on norovirus surrogates, feline calicivirus (FCV) and murine norovirus (MNV), and HAV. Initially, each virus at titers of ca. 6 log TCID50/ml was exposed to different concentrations of natural compounds and incubated for 2h at 37°C. Treatment with oregano and zataria EOs resulted in slight reductions on HAV infectivity with a maximum reduction of less than 0.5 log TCID50/ml at 0.1% zataria EO. Thymol was effective in reducing the titers of norovirus surrogates in a dose-dependent manner. Concentrations of thymol at 0.5 and 1% reduced FCV titers to undetectable levels, while for MNV, thymol at concentrations of 1 and 2% resulted in reductions of 1.66 and 2.45 log TCID50/ml, respectively. However, for HAV, no effect was observed at any of the concentrations tested. These results improve the knowledge about the antiviral activity of EO and their compounds and their potential in food sanitation.

Pressure Inactivation of Enteric Viruses in a Seafood Salad-Like Product

High pressure processing (HPP) is a nonthermal processing technology that can inactivate foodborne viruses. This study assessed the protective effects of food components on virus inactivation by HPP in a seafood salad model. Virus-inoculated seafood samples (cod, shrimp, tuna, and clams) with or without mayonnaise were pressure-treated at 5°C. The seafood salad provided a protective effect on HPP inactivation compared to cell culture medium. Inactivation in seafood salad varied greatly due to the complex nature of the food matrix. When seafood salad ingredients were isolated, mayonnaise alone had a 2.0-log10 PFU/g protective effect for all viruses, unlike albumin, which did not affect virus inactivation, providing some insight into the roles individual ingredients may play on HPP inactivation of viruses in foods.

The efficacy of simulated solar disinfection (SODIS) against coxsackievirus, poliovirus and hepatitis A virus

The antimicrobial activity of simulated solar disinfection (SODIS) against enteric waterborne viruses including coxsackievirus-B5, poliovirus-2 and hepatitis A virus was investigated in this study. Assays were conducted in transparent 12-well polystyrene microtitre plates containing the appropriate viral test suspension. Plates were exposed to simulated sunlight at an optical irradiance of 550 Wm(-2) (watts per square metre) delivered from a SUNTEST™ CPS+ solar simulator for 6 hours. Aliquots of the viral test suspensions were taken at set time points and the level of inactivation of the viruses was determined by either culture on a HeLa cell monolayer for coxsackievirus-B5 and poliovirus-2 or by utilising a chromogenic antibody-based approach for hepatitis A virus. With coxsackievirus-B5, poliovirus-2 and hepatitis A virus, exposure to SODIS at an optical irradiance of 550 Wm(-2) for 1-2 hours resulted in complete inactivation of each virus. The findings from this study suggest that under appropriate conditions SODIS may be an effective technique for the inactivation of enteric viruses in drinking water. However, further verification studies need to be performed using natural sunlight in the region where the SODIS technology is to be employed to validate our results.

The impact of temperature on the inactivation of enteric viruses in food and water: a review

Temperature is considered as the major factor determining virus inactivation in the environment. Food industries, therefore, widely apply temperature as virus inactivating parameter. This review encompasses an overview of viral inactivation and virus genome degradation data from published literature as well as a statistical analysis and the development of empirical formulae to predict virus inactivation. A total of 658 data (time to obtain a first log(10) reduction) were collected from 76 published studies with 563 data on virus infectivity and 95 data on genome degradation. Linear model fitting was applied to analyse the effects of temperature, virus species, detection method (cell culture or molecular methods), matrix (simple or complex) and temperature category (<50 and ≥50°C). As expected, virus inactivation was found to be faster at temperatures ≥50°C than at temperatures <50°C, but there was also a significant temperature-matrix effect. Virus inactivation appeared to occur faster in complex than in simple matrices. In general, bacteriophages PRD1 and PhiX174 appeared to be highly persistent whatever the matrix or the temperature, which makes them useful indicators for virus inactivation studies. The virus genome was shown to be more resistant than infectious virus. Simple empirical formulas were developed that can be used to predict virus inactivation and genome degradation for untested temperatures, time points or even virus strains.

Solar Disinfection of Water for Inactivation of Enteric Viruses and its Enhancement by Riboflavin

Solar disinfection (SODIS) has been described as a cheap and effective method of treating contaminated water to inactivate pathogenic microorganisms. In this study, SODIS was assessed for its efficacy in inactivating three enteric viruses (coxsackievirus B3, coxsackievirus B5 and poliovirus), either on its own or in the presence of riboflavin as a disinfection enhancer. On its own, SODIS produced a reduction of virus infectivity of 4–6 log10 in 6 h. In the presence of riboflavin, inactivation was more rapid in all viruses studied, and with coxsackievirus B5 and poliovirus an extra 1–2 log10 increase in reduction of infectivity was observed after 6 h exposure. This study provides a practical example of low technology methods which could be utilised to provide safe drinking water in various circumstances.

Pathogen inactivation during passage of stormwater through a constructed reedbed and aquifer transfer, storage and recovery

A study was undertaken to determine the potential inactivation rates of selected enteric microorganisms in captured urban stormwater within a constructed reedbed and in tertiary carbonated aquifer during an Aquifer Storage, Transfer and Recovery (ASTR) scheme. The study was undertaken in-situ in the constructed reedbed and aquifer using diffusion chambers. The results showed that all tested bacteria had one log(10) reduction time of less than 6 and 2.5 days respectively in constructed reedbeds and aquifer, which suggests that presence of enteric bacteria in the recovered water is unlikely. However, adenovirus and Cryptosporidium oocysts showed lower inactivation rates with one log(10) reduction times of more than 33 days in the constructed reedbeds. This means that the constructed reedbed with a mean residence time 10 days cannot be relied upon as an efficient treatment barrier for virus and protozoa. Storage of stormwater in aquifer with brackish water resulted in slow inactivation of enteric viruses over the 35 day incubation period with adenovirus and rotavirus showing slowest inactivation times (extrapolated T(90) of >100 days). Cryptosporidium oocysts showed similar inactivation rate in the constructed reedbed and aquifer.

Processing Strategies to Inactivate Enteric Viruses in Shellfish

Noroviruses, hepatitis A and E viruses, sapovirus, astrovirus, rotavirus, Aichi virus, enteric adenoviruses, poliovirus, and other enteroviruses enter shellfish through contaminated seawater or by contamination during handling and processing, resulting in outbreaks ranging from isolated to epidemic. Processing and disinfection methods include shellfish depuration and relaying, cooking and heat pasteurization, freezing, irradiation, and high pressure processing. All the methods can improve shellfish safety; however, from a commercial standpoint, none of the methods can guarantee total virus inactivation without impacting the organoleptic qualities of the shellfish. Noroviruses cause the majority of foodborne viral illnesses, yet there is conflicting information on their susceptibility to inactivation by processing. The inability to propagate and quantitatively enumerate some viral pathogens in vitro or in animal models has led to the use of norovirus surrogates, such as feline calicivirus and murine norovirus. During processing, these surrogates may not mimic the inactivation of the viruses they represent and are, therefore, of limited value. Likewise, reverse transcription-PCR has limited usefulness in monitoring processing effectiveness due to its inability to identify infectious from inactivated viruses. This article (a) describes mechanisms of virus uptake and persistence in shellfish, (b) reviews the state-of-the-art in food processing strategies for the inactivation of enteric viruses in shellfish, (c) suggests the use of combined processing procedures to enhance shellfish safety, (d) highlights limitations in research data derived from virus surrogate studies and molecular assay procedures, and (e) recommends enhanced funding for human volunteer studies and the development of assays to detect viable viruses.

Inactivation of Enteric Viruses in Minimally Processed Berries and Herbs

Several hepatitis A virus (HAV) and human norovirus (HuNoV) outbreaks due to consumption of contaminated berries and vegetables have recently been reported. Model experiments were performed to determine the effectiveness of freeze-drying, freeze-drying combined with heating, and steam blanching for inactivation of enteric viruses that might be present on the surface of berries and herbs. Inactivation of HAV and inactivation of feline calicivirus, a surrogate for HuNoV, were assessed by viral culturing and quantitative reverse transcription PCR (RT-PCR), whereas HuNoV survival was determined only by quantitative RT-PCR. While freeze-drying barely reduced (<1.3 log(10) units) the amount of HAV RNA detected in frozen produce, a greater decline in HAV infectivity was observed. The resistance of HuNoV genogroup I (GI) to freeze-drying was significantly higher than that of HuNoV GII on berries. Addition of a terminal dry heat treatment at 120 degrees C after freeze-drying enhanced virus inactivation by at least 2 log(10) units, except for HuNoV GII. The results suggest that steam blanching at 95 degrees C for 2.5 min effectively inactivated infectious enteric viruses if they were present in herbs. Our results provide data for adjusting food processing technologies if viral contamination of raw materials is suspected.

Chlorine disinfection of produce to inactivate hepatitis A virus and coliphage MS2

Disinfection of produce is principally used to inactivate spoilage microbes and may also reduce the risk of consumer exposure to enteric pathogens. However, the rate and extent of enteric virus inactivation by free chlorine on produce has not been adequately characterized. Experiments were performed to determine the kinetics of free chlorine inactivation of hepatitis A virus (HAV) and the indicator virus coliphage MS2 on strawberries (SBs), cherry tomatoes (CTs), and head lettuce (HL). The oxidant demand of these produce items also was determined. When produce items were exposed to approximately 20 parts per million (ppm) solution of free chlorine for 5–10 min, HAV and MS2 were inactivated by 90–99% and in some cases virus inactivation was ≥ 99%. Exposure of strawberries to approximately 200 ppm free chlorine resulted in more rapid and extensive inactivation of both viruses. The produce items tested in this study exhibited a demand for chlorine which varied by produce type, and chlorine residuals declined over time. These results demonstrate the potential for chlorine to reduce the levels of infectious viruses on different produce types, but adequate contact time and chlorine residual are required to achieve maximum virus inactivation. The difference in chlorine demand between SBs, CTs, and HL suggests that varying disinfection practices are needed for the wide variety of processed fruits and vegetables. The inactivation kinetics of MS2 and HAV were similar, suggesting that MS2 and perhaps other similar bacterial viruses may be used as process indicators and surrogates for determining the disinfection efficacy of produce in the laboratory or in actual practice.

Enteric Virus Survival during Household Laundering and Impact of Disinfection with Sodium Hypochlorite

This study was conducted to determine whether enteric viruses (adenovirus, rotavirus, and hepatitis A virus) added to cotton cloth swatches survive the wash cycle, the rinse cycle, and a 28-min permanent press drying cycle as commonly practiced in households in the United States. Detergent with and without bleach (sodium hypochlorite) was added to washing machines containing sterile and virus-inoculated 58-cm2 swatches, 3.2 kg of cotton T-shirts and underwear, and a soiled pillowcase designed to simulate the conditions (pH, organic load, etc.) encountered in soiled laundry. The most important factors for the reduction of virus in laundry were passage through the drying cycle and the addition of sodium hypochlorite. Washing with detergent alone was not found to be effective for the removal or inactivation of enteric viruses, as significant concentrations of virus were found on the swatches (reductions of 92 to 99%). It was also demonstrated that viruses are readily transferred from contaminated cloths to uncontaminated clothes. The use of sodium hypochlorite reduced the number of infectious viruses on the swatches after washing and drying by at least 99.99%. Laundering practices in common use in the United States do not eliminate enteric and respiratory viruses from clothes. The use of bleach can further reduce the numbers of enteric viruses in laundry.

Virus inactivation during disinfection of wastewater by chlorination and UV irradiation and the efficacy of F+ bacteriophage as a ‘viral indicator’

Wastewater disinfection has grown in popularity in recent years in the UK particularly for reducing faecal coliform levels in effluents impacting on bathing waters not compliant with EC Directive standards. Although disinfectants appear effective against bacterial indicators of faecal pollution, their efficiency against human viruses is still unclear. This has significance both for attainment of compliance with viral standards in the EC Bathing Waters Directive and, potentially, for protection against viruses likely to cause gastroenteritis. This study reports on bench scale disinfection of primary effluent treated with chlorination and secondary effluent treated with UV. Disinfection experiments comprised of wastewater, sterilised by gamma irradiation, seeded with monodispersed laboratory grown bacterial indicators (Escherichia coli and Enterococcus faecalis), human enterovirus (poliovirus) and F+ bacteriophage (MS2) – a potential ‘viral indicator’. Under the experimental conditions used, the inactivation of bacterial indicators was rapid in comparison to the inactivation of F+ bacteriophage which was very poor. Seeded poliovirus was significantly more susceptible to inactivation by chlorine and UV irradiation than F+ bacteriophage but was more resistant than bacterial indicators in both cases. These results indicate that the use of bacterial indicators alone to determine the effect of wastewater disinfection when using chlorination or UV irradiation underestimates human enteric virus inactivation, whereas the use of F+ bacteriophage is likely to give a conservative estimate of virus inactivation.