Effect of temperature, pH, and NaCl on the inactivation kinetics of murine norovirus

Assessing infectivity of emerging enveloped viruses in wastewater and sewage sludge: Relevance and procedures

The emergence of SARS-CoV-2 has heightened the need to evaluate the detection of enveloped viruses in the environment, particularly in wastewater, within the context of wastewater-based epidemiology. The studies published over the past 80 years focused primarily on non-enveloped viruses due to their ability to survive longer in environmental matrices such as wastewater or sludge compared to enveloped viruses. However, different enveloped viruses survive in the environment for different lengths of time. Therefore, it is crucial to be prepared to assess the potential infectious risk that may arise from future emerging enveloped viruses. This will require appropriate tools, notably suitable viral concentration methods that do not compromise virus infectivity. This review has a dual purpose: first, to gather all the available literature on the survival of infectious enveloped viruses, specifically at different pH and temperature conditions, and in contact with detergents; second, to select suitable concentration methods for evaluating the infectivity of these viruses in wastewater and sludge. The methodology used in this data collection review followed the systematic approach outlined in the PRISMA (Preferred Reporting Items for Systematic Review and Meta-Analysis) guidelines. Concentration methods cited in the data gathered are more tailored towards detecting the enveloped viruses' genome. There is a lack of suitable methods for detecting infectious enveloped viruses in wastewater and sludge. Ultrafiltration, ultracentrifugation, and polyethylene glycol precipitation methods, under specific/defined conditions, appear to be relevant approaches. Further studies are necessary to validate reliable concentration methods for detecting infectious enveloped viruses. The choice of culture system is also crucial for detection sensitivity. The data also show that the survival of infectious enveloped viruses, though lower than that of non-enveloped ones, may enable environmental transmission. Experimental data on a wide range of enveloped viruses is required due to the variability in virus persistence in the environment.

Virus rejection and removal in pilot-scale air-gap membrane distillation

Membrane distillation (MD) is a thermally-driven process that can treat high concentration streams and provide a dual barrier for rejection and reduction of pathogens. Thus, MD has potential applications in treating concentrated wastewater brines for enhancing water recovery and potable water reuse. In bench-scale studies, it was demonstrated that MD can provide high rejection of MS2 and PhiX174 bacteriophage viruses, and when operating at temperatures greater than 55 °C, can reduce virus levels in the concentrate. However, bench-scale MD results cannot directly be used to predict pilot-scale contaminant rejection and removal of viruses because of the lower water flux and higher transmembrane hydraulic pressure difference in pilot-scale systems. Thus far, virus rejection and removal have not been quantified in pilot-scale MD systems. In this work, the rejection of MS2 and PhiX174 at low (40 °C) and high (70 °C) inlet temperatures is quantified in a pilot-scale air-gap MD system using tertiary treated wastewater. Both viruses were detected in the distillate which suggests the presence of pore flow; the virus rejection at a hot inlet temperature of 40 °C for MS2 and PhiX174 were 1.6-log₁₀ and 3.1-log₁₀, respectively. At 70 °C, virus concentrations in the brine decreased and were below the detection limit (1 PFU per 100 mL) after 4.5 h, however, viruses were also detected in the distillate in that duration. Results demonstrate that virus rejection is lower in pilot-scale experiments because of increased pore flow that is not captured in bench-scale experiments.

Sources, fates and treatment strategies of typical viruses in urban sewage collection/treatment systems: A review

The ongoing coronavirus pandemic (COVID-19) throughout the world has severely threatened the global economy and public health. Due to receiving severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from a wide variety of sources (e.g., households, hospitals, slaughterhouses), urban sewage treatment systems are regarded as an important path for the transmission of waterborne viruses. This review presents a quantitative profile of the concentration distribution of typical viruses within wastewater collection systems and evaluates the influence of different characteristics of sewer systems on virus species and concentration. Then, the efficiencies and mechanisms of virus removal in the units of wastewater treatment plants (WWTPs) are summarized and compared, among which the inactivation efficiencies of typical viruses by typical disinfection approaches under varied operational conditions are elucidated. Subsequently, the occurrence and removal of viruses in treated effluent reuse and desalination, as well as that in sewage sludge treatment, are discussed. Potential dissemination of viruses is emphasized by occurrence via aerosolization from toilets, the collection system and WWTP aeration, which might have a vital role in the transmission and spread of viruses. Finally, the frequency and concentration of viruses in reclaimed water, the probability of infection are also reviewed for discussing the potential health risks.

Occurrence of bacterial and viral fecal markers in municipal sewage sludge and their removal during sludge conditioning processes

Fecal contamination in wastewater treatment system may pose severe threats to human health, but the detailed contamination of fecal bacterial and viral pathogens in municipal sewage sludge remains unclear. In addition, it is also unclear how sludge conditioning treatments would impact the distribution of fecal markers in conditioned sewage sludge. Before addressing these two issues, the possible polymerase chain reaction (PCR) inhibition effect when determining the abundances of fecal markers in both sludge solids and sludge supernatants should be solved, and methods of effectively concentrating fecal markers from sludge supernatant should also be developed. In the present study, we found that the serial tenfold dilution effectively reduced the PCR inhibition effect when determining the abundances of fecal markers including cross-assembly phages (CrAssphage), JC polyomavirus (JCPyV), human-specific HF183 bacteroides (HF183), human BK polyomavirus (BKPyV), human adenovirus (HAdV) and Escherichia coli (EC), while the utilization of negatively charged HA membrane was effective to recover fecal markers from sludge supernatant. The results of a six-month monitoring revealed that gene markers of CrAssphage, JCPyV, HF183, BKPyV, HAdV, and EC can be detected in municipal sewage sludge collected from a local wastewater treatment plant. Among the investigated four chemical conditioning methods, i.e., chemical conditioning with polyacrylamide (PAM), Fe[III]/CaO, or Fenton's reagent, and chemical acidification conditioning, chemical conditioning with Fenton's reagent was much more effective than the other three conditioning methods to reduce the abundances of fecal markers in the supernatant and solid of conditioned sewage sludge. Furthermore, the investigated fecal markers in the conditioned sewage sludge can be simultaneously attenuated by employing suitable conditioning methods, consequently reducing the associated environmental risks.

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.

Solar Water Disinfection to Produce Safe Drinking Water: A Review of Parameters, Enhancements, and Modelling Approaches to Make SODIS Faster and Safer

Solar water disinfection (SODIS) is one the cheapest and most suitable treatments to produce safe drinking water at the household level in resource-poor settings. This review introduces the main parameters that influence the SODIS process and how new enhancements and modelling approaches can overcome some of the current drawbacks that limit its widespread adoption. Increasing the container volume can decrease the recontamination risk caused by handling several 2 L bottles. Using container materials other than polyethylene terephthalate (PET) significantly increases the efficiency of inactivation of viruses and protozoa. In addition, an overestimation of the solar exposure time is usually recommended since the process success is often influenced by many factors beyond the control of the SODIS-user. The development of accurate kinetic models is crucial for ensuring the production of safe drinking water. This work attempts to review the relevant knowledge about the impact of the SODIS variables and the techniques used to develop kinetic models described in the literature. In addition to the type and concentration of pathogens in the untreated water, an ideal kinetic model should consider all critical factors affecting the efficiency of the process, such as intensity, spectral distribution of the solar radiation, container-wall transmission spectra, ageing of the SODIS reactor material, and chemical composition of the water, since the substances in the water can play a critical role as radiation attenuators and/or sensitisers triggering the inactivation process.

Room Temperature Wait and Reuse for Bioburden Reduction of SARS-CoV-2 on N95 Filtering Facepiece Respirators

Introduction: During a pandemic, when the supply of N95 filtering facepiece respirators (FFRs) is limited, health care workers may reuse N95 FFRs. Room temperature storage of N95 FFRs-waiting before reuse-could be a simple low-cost method to reduce severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) bioburden in such a situation. The U.S. Centers for Disease Control and Prevention specify this as a strategy for reducing self-contamination risk during a time of N95 FFR shortage. Objective: To review the literature on persistence of SARS-CoV-2 on surfaces to assess room temperature waiting times for bioburden reduction on N95 FFRs. Methods: The literature was searched for studies evaluating room temperature persistence of SARS-CoV-2. A 3-log decay time was extracted from published data for quantitative comparison between different studies. Studies using surgical masks and non-peer-reviewed studies that include N95 FFRs were used to draw conclusions. Key Findings: Experimental and analytical choices vary between studies and impact the estimated 3-log decay time. There is not a clear understanding of which material properties are significant. There are no peer-reviewed studies of virus persistence on an N95 FFR. Discussion and Conclusions: SARS-COV-2 inactivation occurs spontaneously at room temperature. The precise timing depends on factors including humidity, temperature, and surface material. In reviewed studies, a 7-day waiting period encompasses the 3-log reduction in infectious titer of SARS-COV-2 on specific N95 FFRs and surgical masks. Owing to variations between studies and among N95 FFR materials and room temperature conditions, it is impossible to extrapolate from these limited data to assign a precise 3-log decay time for all used N95 FFRs.

A chronicle of SARS-CoV-2: Seasonality, environmental fate, transport, inactivation, and antiviral drug resistance

In this review, we present the environmental perspectives of the viruses and antiviral drugs related to SARS-CoV-2. The present review paper discusses occurrence, fate, transport, susceptibility, and inactivation mechanisms of viruses in the environment as well as environmental occurrence and fate of antiviral drugs, and prospects (prevalence and occurrence) of antiviral drug resistance (both antiviral drug resistant viruses and antiviral resistance in the human). During winter, the number of viral disease cases and environmental occurrence of antiviral drug surge due to various biotic and abiotic factors such as transmission pathways, human behaviour, susceptibility, and immunity as well as cold climatic conditions. Adsorption and persistence critically determine the fate and transport of viruses in the environment. Inactivation and disinfection of virus include UV, alcohol, and other chemical-base methods but the susceptibility of virus against these methods varies. Wastewater treatment plants (WWTPs) are major reserviors of antiviral drugs and their metabolites and transformation products. Ecotoxicity of antiviral drug residues against aquatic organisms have been reported, however more threatening is the development of antiviral resistance, both in humans and in wild animal reservoirs. In particular, emergence of antiviral drug-resistant viruses via exposure of wild animals to high loads of antiviral residues during the current pandemic needs further evaluation.

Membrane Distillation Provides a Dual Barrier for Coronavirus and Bacteriophage Removal

The persistence of pathogenic microorganisms in treated wastewater effluent makes disinfection crucial to achieve wastewater reuse. Membrane processes such as ultrafiltration and reverse osmosis (RO) have shown promising results for virus and other contaminant removal from treated wastewater effluents for reuse application. However, RO produces a concentrate stream which contains high concentrations of pathogens and contaminants that often requires treatment and volume reduction before disposal. Membrane distillation (MD) is a treatment process that can reduce RO concentrate volume while augmenting the potable water supply. MD is also a dual barrier approach for virus removal as it operates at a high temperature and permeates only the vapor phase through the membrane interface. The effects of temperature on viable virus concentration and membrane rejection of viruses in MD are investigated in this study using two nonenveloped phages frequently used as enteric virus surrogates (MS2 and PhiX174) and an enveloped pathogenic virus (HCoV-229E). At typical MD operating temperatures (greater than 65 °C), viable concentrations of all three viruses were reduced by thermal inactivation by more than 6-log10 for MS2 and PhiX174 and more than 3-log10 for HCoV-229E. Also, membrane rejection was greater than 6-log10 for MS2 and PhiX174 and greater than 2.5-log10 for HCoV-229E.

Survival of MS2 and Φ6 viruses in droplets as a function of relative humidity, pH, and salt, protein, and surfactant concentrations

The survival of viruses in droplets is known to depend on droplets' chemical composition, which may vary in respiratory fluid between individuals and over the course of disease. This relationship is also important for understanding the persistence of viruses in droplets generated from wastewater, freshwater, and seawater. We investigated the effects of salt (0, 1, and 35 g/L), protein (0, 100, and 1000 μg/mL), surfactant (0, 1, and 10 μg/mL), and droplet pH (4.0, 7.0, and 10.0) on the viability of viruses in 1-μL droplets pipetted onto polystyrene surfaces and exposed to 20%, 50%, and 80% relative humidity (RH) using a culture-based approach. Results showed that viability of MS2, a non-enveloped virus, was generally higher than that of Φ6, an enveloped virus, in droplets after 1 hour. The chemical composition of droplets greatly influenced virus viability. Specifically, the survival of MS2 was similar in droplets at different pH values, but the viability of Φ6 was significantly reduced in acidic and basic droplets compared to neutral ones. The presence of bovine serum albumin protected both MS2 and Φ6 from inactivation in droplets. The effects of sodium chloride and the surfactant sodium dodecyl sulfate varied by virus type and RH. Meanwhile, RH affected the viability of viruses as shown previously: viability was lowest at intermediate to high RH. The results demonstrate that the viability of viruses is determined by the chemical composition of carrier droplets, especially pH and protein content, and environmental factors. These findings emphasize the importance of understanding the chemical composition of carrier droplets in order to predict the persistence of viruses contained in them.

Energy Requirements for Loss of Viral Infectivity

Outside the host, viruses will eventually lose their ability to infect cells due to conformational changes that occur to proteins on the viral capsid. In order to undergo a conformational change, these proteins require energy to activate the chemical reaction that leads to the conformational change. In this study, data from the literature is used to calculate the energy required for viral inactivation for a variety of different viruses by means of the Arrhenius equation. We find that some viruses (rhinovirus, poliovirus, human immunodeficiency virus, Alkhumra hemorrhagic fever virus, and hepatitis A virus) have high inactivation energies, indicative of breaking of a chemical double bond. We also find that several viruses (respiratory syncytial virus, poliovirus, and norovirus) have nonlinear Arrhenius plots, suggesting that there is more than a single pathway for inactivation of these viruses.

Modeling the photoinactivation and transport of somatic and F-specific coliphages at a Great Lakes beach

Fecal indicator organisms (FIOs), such as Escherichia coli and enterococci, are often used as surrogates of contamination in the context of beach management; however, bacteriophages may be more reliable indicators than FIO due to their similarity to viral pathogens in terms of size and persistence in the environment. In the past, mechanistic modeling of environmental contamination has focused on FIOs, with virus and bacteriophage modeling efforts remaining limited. In this paper, we describe the development and application of a fate and transport model of somatic and F-specific coliphages for the Washington Park beach in Lake Michigan, which is affected by riverine outputs from the nearby Trail Creek. A three-dimensional model of coliphage transport and photoinactivation was tested and compared with a previously reported E. coli fate and transport model. The light-based inactivation of the phages was modeled using organism-specific action spectra. Results indicate that the coliphage models outperformed the E. coli model in terms of reliably predicting observed E. coli/coliphage concentrations at the beach. This is possibly due to the presence of additional E. coli sources that were not accounted for in the modeling. The coliphage models can be used to test hypotheses about potential sources and their behavior and for predictive modeling.

Survival of Human Norovirus Surrogates in Water upon Exposure to Thermal and Non-Thermal Antiviral Treatments

Human noroviruses are the leading cause of foodborne gastroenteritis worldwide and disease outbreaks have been linked to contaminated surface waters as well as to produce consumption. Noroviruses are extremely stable in water and their presence is being detected with increasing frequency, yet there are no viable methods for reducing norovirus contamination in environmental water. Despite this, there is little knowledge regarding the physical and chemical factors that influence the environmental persistence of this pathogen. This study evaluated the impact of common chemical and physical properties of surface water on the stability of murine norovirus and examined the effect of food-safe chitosan microparticles on infectivity of two human norovirus surrogates. While chemical additives had a minor impact on virus survival, chitosan microparticles significantly reduced infectious titers of both murine norovirus and MS2 bacteriophage.

A Survey of Analytical Techniques for Noroviruses

As the leading cause of acute gastroenteritis worldwide, human noroviruses (HuNoVs) have caused around 685 million cases of infection and nearly $60 billion in losses every year. Despite their highly contagious nature, an effective vaccine for HuNoVs has yet to become commercially available. Therefore, rapid detection and subtyping of noroviruses is crucial for preventing viral spread. Over the past half century, there has been monumental progress in the development of techniques for the detection and analysis of noroviruses. However, currently no rapid, portable assays are available to detect and subtype infectious HuNoVs. The purpose of this review is to survey and present different analytical techniques for the detection and characterization of noroviruses.

Preparation of hydrophobic La2Mo2O9 ceramics with antibacterial and antiviral properties

After powder of La₂Mo₂O₉ (LMO) was prepared using complex polymerization, dense sintered bodies (96% relative density) of LMO were obtained from the powder through pressureless sintering in a synthesized air atmosphere. The water contact angle of the LMO ceramics increased gradually during storage in ambient air. It reached 93.6 ± 3.0° in 624 h. Results of XPS analysis and ozone treatment suggest that organic substances in ambient air adsorbed onto the LMO surface during storage. Measurements of antibacterial (Escherichia coli and Staphylococcus aureus) and antiviral (bacteriophage Qβ and bacteriophage Φ6) activities of LMO revealed that their survival rates decreased more than 99.9% within 6 h. Based on results obtained using dissolved ion contact method and from comparison of the antibacterial and antiviral activities with La₂O₃ and MoO₃, one can infer that the synergistic effect of La₂O₃ and MoO₃ plays an important role in the high antibacterial and antiviral activity of LMO.

[Inactivating Effect of Heat-Denatured Lysozyme on Murine Norovirus in Bread Fillings]

In this study, we investigated the viability of murine norovirus strain 1 (MNV-1), a surrogate for human norovirus, in bread fillings used for making stuffed buns and pastries. The inactivating effect of heat-denatured lysozyme, which was recently reported to have an antiviral effect, on MNV-1 contaminating the bread fillings was also examined. MNV-1 was inoculated into two types of fillings (chocolate cream, marmalade jam) at 4.5 log PFU/g, and the bread fillings were stored at 4℃ for 5 days. MNV-1 remained viable in the bread fillings during storage. However, addition of 1% heat-denatured lysozyme to the fillings resulted in a decrease of MNV-1 infectivity immediately after inoculation, in both fillings. On the fifth day of storage, MNV-1 infectivity was decreased by 1.2 log PFU/g in chocolate cream and by 0.9 log PFU/g in marmalade jam. Although the mechanism underlying the anti-norovirus effect of heat-denatured lysozyme has not been clarified, our results suggest that heat-denatured lysozyme can be used as an inactivating agent against norovirus in bread fillings.

Antiviral Effects of Houttuynia cordata Polysaccharide Extract on Murine Norovirus-1 (MNV-1)-A Human Norovirus Surrogate

Houttuynia cordata is an herbal plant rich in polysaccharides and with several pharmacological activities. Human noroviruses (HuNoVs) are the most common cause of foodborne viral gastroenteritis throughout the world. In this study, H. cordata polysaccharide (HP), with a molecular weight of ~43 kDa, was purified from H. cordata water extract (HWE). The polysaccharide HP was composed predominantly of galacturonic acid, galactose, glucose, and xylose in a molar ratio of 1.56:1.49:1.26:1.11. Methylation and NMR analyses revealed that HP was a pectin-like acidic polysaccharide mainly consisting of α-1,4-linked GalpA, β-1,4-linked Galp, β-1,4-linked Glcp, and β-1,4-linked Xylp residues. To evaluate the antiviral activity of H. cordata extracts, we compared the anti-norovirus potential of HP with HWE and ethanol extract (HEE) from H. cordata by plaque assay (plaque forming units (PFU)/mL) for murine norovirus-1 (MNV-1), a surrogate of HuNoVs. Viruses at high (8.09 log10 PFU/mL) or low (4.38 log10 PFU/mL) counts were mixed with 100, 250, and 500 μg/mL of HP, HWE or HEE and incubated for 30 min at room temperature. H. cordata polysaccharide (HP) was more effective than HEE in reducing MNV-1 plaque formation, but less effective than HWE. When MNV-1 was treated with 500 μg/mL HP, the infectivity of MNV-1 decreased to an undetectable level. The selectivity indexes of each sample were 1.95 for HEE, 5.74 for HP, and 16.14 for HWE. The results of decimal reduction time and transmission electron microscopic revealed that HP has anti-viral effects by deforming and inflating virus particles, thereby inhibiting the penetration of viruses in target cells. These findings suggest that HP might have potential as an antiviral agent in the treatment of viral diseases.

Efficacy of Silver Dihydrogen Citrate and Steam Vapor against a Human Norovirus Surrogate, Feline Calicivirus, in Suspension, on Glass, and on Carpet

Carpets and other soft surfaces have been associated with prolonged and reoccurring human norovirus (HuNoV) outbreaks. Environmental hygiene programs are important to prevent and control HuNoV outbreaks. Despite our knowledge of HuNoV transmission via soft surfaces, no commercially available disinfectants have been evaluated on carpets. Our aim was to adapt a current standardized method for virucidal testing by assessing two disinfection technologies, silver dihydrogen citrate (SDC) and steam vapor, against one HuNoV surrogate, feline calicivirus (FCV), on wool and nylon carpets. First, we evaluated the effect of both technologies on the appearance of carpet. Next, we evaluated the efficacy of SDC in suspension and the efficacy of SDC and steam vapor against FCV on a glass surface, each with and without serum. Lastly, we tested both technologies on two types of carpet, wool and nylon. Both carpets exhibited no obvious color changes; however, SDC treatments left a residue while steam vapor left minor abrasions to fibers. SDC in suspension and on glass reduced FCV by 4.65 log10 and >4.66 log10 PFU, respectively, but demonstrated reduced efficacy in the presence of serum. However, SDC was only efficacious against FCV on nylon (3.62-log10 PFU reduction) and not wool (1.82-log10 PFU reduction). Steam vapor reduced FCV by >4.93 log10 PFU on glass in 10 s and >3.68 log10 PFU on wool and nylon carpet carriers in 90 s. There was a limited reduction of FCV RNA under both treatments compared to that of infectivity assays, but RNA reductions were higher in samples that contained serum.IMPORTANCE Human noroviruses (HuNoV) account for ca. 20% of all diarrheal cases worldwide. Disease symptoms may include diarrhea and vomit, with both known to contribute to transmission. The prevention and control of HuNoV are difficult because they are environmentally resilient and resistant to many disinfectants. Several field studies have linked both hard and soft surfaces to HuNoV outbreaks. However, many disinfectants efficacious against HuNoV surrogates are recommended for hard surfaces, but no commercially available products have demonstrated efficacy against these surrogates on soft surfaces. Our research objectives were to evaluate liquid and steam-based technologies in suspension and on hard surface carriers in addition to adapting and testing a protocol for assessing the virucidal effects of disinfection technologies on carpet carriers. These results will inform both the government and industry regarding a standard method for evaluating the virucidal effects of disinfectants on carpet while demonstrating their efficacy relative to suspension and hard-surface tests.

Identification of the inactivating factors and mechanisms exerted on MS2 coliphage in concentrated synthetic urine

Volume reduction (condensation) is a key for the practical usage of human urine as a fertilizer because it enables the saving of storage space and the reduction of transportation cost. However, concentrated urine may carry infectious disease risks resulting from human pathogens frequently present in excreta, though the survival of pathogens in concentrated urine is not well understood. In this study, the inactivation of MS2 coliphage, a surrogate for single-stranded RNA human enteric viruses, in concentrated synthetic urine was investigated. The infectious titer reduction of MS2 coliphage in synthetic urine samples was measured by plaque assay, and the reduction of genome copy number was monitored by reverse transcription-quantitative PCR (RTqPCR). Among chemical-physical conditions such as pH and osmotic pressure, uncharged ammonia was shown to be the predominant factor responsible for MS2 inactivation, independently of urine concentration level. The reduction rate of the viral genome number varied among genome regions, but the comprehensive reduction rate of six genome regions was well correlated with that of the infectious titer of MS2 coliphage. This indicates that genome degradation is the main mechanism driving loss of infectivity, and that RT-qPCR targeting the six genome regions can be used as a culture-independent assay for monitoring infectivity loss of the coliphage in urine. MS2 inactivation rate constants were well predicted by a model using ion composition and speciation in synthetic urine samples, which suggests that MS2 infectivity loss can be estimated solely based on the solution composition, temperature and pH, without explicitly accounting for effects of osmotic pressure.

Virucidal efficacy of food additive grade calcium hydroxide against surrogate of human norovirus

An alkaline agent, namely, food additive grade calcium hydroxide (FdCa(OH)₂) in the solution, powder and suspension forms was evaluated as a virucidal agent, using a murine norovirus (MNV) as the surrogate for human norovirus. The main constituent of FdCa(OH)₂ is Ca(OH)₂, which has pH 13 in 0.17% solution. The results showed that 0.17% FdCa(OH)₂ solution could inactivate MNV within 30s even in the presence of organic materials (5% fetal bovine serum (FBS)). In a contaminated surface experiment, MNV with 5% FBS was inoculated on rayon sheets, and the result showed FdCa(OH)₂ solution could markedly reduce virus titer within 1min. When mouse feces were spiked with MNV and FdCa(OH)₂ powder as 10% and 20% w/w was added to the feces, these concentrations could inactivate the virus within 30min and 15min, respectively. Whereas, FdCa(OH)₂ suspension at 2.5% and 5% could inactivate the virus within 30min and at 1% within 45min. These and additional results obtained here indicate that FdCa(OH)₂ is an effective virucidal agent against MNV, and can serve as a useful alternative disinfectant for inactivation and prevention of human norovirus in house and hospital.

Inactivation of Norovirus by Lemongrass Essential Oil Using a Norovirus Surrogate System

This study investigated the effect of lemongrass essential oil (LGEO) on the infectivity and viral replication of norovirus. Murine norovirus 1 (MNV-1), a surrogate of human norovirus, was preincubated with LGEO and then used to infect RAW 264.7 cells in a plaque reduction assay. LGEO exhibited a significant reduction in MNV-1 plaque formation in both time- and dose-dependent manners. The quantification of viral genome by quantitative real-time PCR showed similar results in line with those of the plaque reduction assay. It was revealed that citral, a single compound in LGEO, showed dramatic reduction in MNV-1 infectivity (-73.09% when using a treatment of 0.02%, v/v). The inhibitory activity of LGEO on viral replication was further investigated in HG23 cells that harbored a human norovirus replicon. LGEO treatment significantly reduced viral replication in HG23 cells, which suggests that LGEO may have dual inhibitory activities that inactivate viral coat proteins required for viral infection and suppress norovirus genome replication in host cells. In animal experiments, oral administration of murine norovirus preincubated with LGEO significantly suppressed virus infectivity in vivo. Collectively, these results suggest that LGEO, in particular the LGEO component citral, inactivates the norovirus and its subsequent replication in host cells. Thus, LGEO shows promise as a method of inhibiting norovirus within the food industry.

Inactivation of Viruses and Bacteriophages as Models for Swine Hepatitis E Virus in Food Matrices

Hepatitis E virus has been recognised as a food-borne virus hazard in pork products, due to its zoonotic properties. This risk can be reduced by adequate treatment of the food to inactivate food-borne viruses. We used a spectrum of viruses and bacteriophages to evaluate the effect of three food treatments: high pressure processing (HPP), lactic acid (LA) and intense light pulse (ILP) treatments. On swine liver at 400 MPa for 10 min, HPP gave log₁₀ reductions of ≥4.2, ≥5.0 and 3.4 for feline calicivirus (FCV) 2280, FCV wildtype (wt) and murine norovirus 1 (MNV 1), respectively. Escherichia coli coliphage ϕX174 displayed a lower reduction of 1.1, while Escherichia coli coliphage MS2 was unaffected. For ham at 600 MPa, the corresponding reductions were 4.1, 4.4, 2.9, 1.7 and 1.3 log₁₀. LA treatment at 2.2 M gave log₁₀ reductions in the viral spectrum of 0.29-2.1 for swine liver and 0.87-3.1 for ham, with ϕX174 and MNV 1, respectively, as the most stable microorganisms. The ILP treatment gave log₁₀ reductions of 1.6-2.8 for swine liver, 0.97-2.2 for ham and 1.3-2.3 for sausage, at 15-60 J cm^-2, with MS2 as the most stable microorganism. The HPP treatment gave significantly (p < 0.05) greater virus reduction on swine liver than ham for the viruses at equivalent pressure/time combinations. For ILP treatment, reductions on swine liver were significantly (p < 0.05) greater than on ham for all microorganisms. The results presented here could be used in assessments of different strategies to protect consumers against virus contamination and in advice to food producers. Conservative model indicators for the pathogenic viruses could be suggested.

Differences in the viability of murine norovirus in different aquatic locations

Norovirus is detected from shellfish and environmental water more frequently in winter than in other seasons. However, there is no report regarding its viability in actual seawater in situ. We investigated the viability of murine norovirus strain 1 (MNV-1), a surrogate for human norovirus, in 2 types of aquatic locations, a seawater pool carrying oceanic water and inner bay carrying brackish water. Sterilized seawater was inoculated with MNV-1 and enclosed in dialysis tubes, which were placed at the 2 locations. MNV-1 exhibited higher level of viability in brackish than in oceanic water. Factors that influenced the viability of MNV-1 included salt concentration as well as temperature of the seawater. Therefore, based on our findings, coastal brackish water that is routinely used for harvesting or cleaning seafood at fishing ports may promote the viability of norovirus.

Antimicrobial effects of vinegar against norovirus and Escherichia coli in the traditional Korean vinegared green laver (Enteromorpha intestinalis) salad during refrigerated storage

In Korea, edible seaweeds are potentially regarded as high-risk foods with respect to enteric norovirus (NoV) and non-pathogenic generic Escherichia coli. This study investigated the antimicrobial effects of 5%, 10%, and 15% vinegar (6% acetic acid) on the survival of murine norovirus-1 (MNV-1), a human NoV surrogate, and E. coli, a fecal indicator in experimentally contaminated raw fresh green lavers (Enteromorpha intestinalis) during a 7-d storage period at 4°C. Both MNV-1 titers and E. coli counts significantly (p<0.05) decreased with stepwise increase in vinegar concentration and storage time, except in E. coli of the 0% vinegar-containing lavers; however, MNV-1 was more resistant to vinegar than E. coli. The overall average MNV-1 titers were significantly (p<0.05) higher in 0% vinegar-containing lavers (3.6log₁₀PFU/ml) than in 5-15% vinegar-containing lavers (3.3-3.1log₁₀PFU/ml) throughout the 7days of storage. A 1-log reduction in the MNV-1 titer was observed in 0% vinegar-containing laver samples after 5days of storage and 5-15% vinegar-containing laver samples after 3days of storage. The overall E. coli count was also significantly (p<0.05) decreased in the 15% (6.8log₁₀CFU/g) vinegar-containing lavers than in the 10% (7.3log₁₀CFU/g) and 5% (7.6log₁₀CFU/g) vinegar-containing lavers. A >1-log reduction in the E. coli count was observed in 10-15% vinegar-containing laver samples just after 1day of storage. A 2-log reduction in the E. coli count was also observed in 10-15% vinegar-containing laver samples after 5days of storage. Using the non-linear Weibull model, this study showed that the d_R-values (1-log reduction) of MNV-1 were 4.90days for 0%, 4.28days for 5%, 3.79days for 10%, and 2.88days for 15% vinegar-containing lavers, whereas those for E. coli were 1.12day for 5%, 1.03day for 10%, and 0.90day for 15% vinegar-containing lavers stored at 4°C. Vinegar with over the storage time can be used as an antimicrobial ingredient against NoV and E. coli in Korean conventional foods. Specifically, this study suggests that ~1day of storage is required for 1-log reduction in the E. coli count in the vinegar-containing (5-15%) lavers, whereas 3-5days of storage at 4°C is adequate for 1-log reduction in the MNV-1 count in the vinegar-containing and non-vinegar-containing lavers.

Effect of Process Temperature on Virus Inactivation during High Hydrostatic Pressure Processing of Contaminated Fruit Puree and Juice

High pressure processing (HPP) can inactivate pathogens and retain fruit qualities. Elevated HPP pressure or time increases virus inactivation, but the effect of temperature is not consistently observed for norovirus and hepatitis A virus. In the present study, the effectiveness of HPP holding temperatures (<40°C) and pressures were evaluated for inactivating surrogates (murine norovirus [MNV] and MS2 coliphage) in pomegranate and strawberry juices and strawberry puree using a 24-liter HPP system. The holding temperature was established by setting the HPP initial temperature via pretrials. All trials were able to arrive at the designated holding pressure and holding temperature simultaneously. MNV inactivation in juices was conducted at 300 MPa for 3 min with various holding temperatures (10 to 30°C). A regression equation was derived, Y = -0.08 × X + 2.6 log PFU, R² = 0.96, where Y is the log reduction and X is the holding temperature. The equation was used to predict a 2.6-log reduction in juices at 0°C holding temperature and indicated that MNV inactivation was inversely proportional to temperature increase. MNV survival during HPP did not differ significantly in pomegranate and strawberry juices. However, MS2 coliphage inactivation was greater as the holding temperature increased (from 15 to 38°C) at 600 MPa for 3 min. The increased inactivation trend is presumably similar to that for hepatitis A virus, but the holding temperature was not correlated with the reduction of HPP-resistant MS2 in strawberry puree. When the HPP holding pressure was evaluated independently in strawberry puree, a 5-log reduction of MNV was predicted through regression analysis at the holding pressure of 424 MPa for 3 min at 20°C. These parameters should inactivate >5 log PFU of MNV in juices, based upon a greater inactivation in berry juice than in puree (1.16-versus 0.74-log reduction at 300 MPa). This research illustrates use of predictive inactivation and a feasible means for manipulating HPP parameters for effective virus inactivation in fruit juices and puree.

Validation of γ-radiation and ultraviolet as a new inactivators for foot and mouth disease virus in comparison with the traditional methods

AIM

The present work deals with different methods for foot and mouth disease virus (FMDV) inactivation for serotypes O/pan Asia, A/Iran05, and SAT-2/2012 by heat, gamma radiation, and ultraviolet (UV) in comparison with the traditional methods and their effects on the antigenicity of viruses for production of inactivated vaccines.

MATERIALS AND METHODS

FMDV types O/pan Asia, A/Iran05, and SAT-2/2012 were propagated in baby hamster kidney 21 (BHK21) and titrated then divided into five parts; the first part inactivated with heat, the second part inactivated with gamma radiation, the third part inactivated with UV light, the fourth part inactivated with binary ethylamine, and the last part inactivated with combination of binary ethylamine and formaldehyde (BEI+FA). Evaluate the method of inactivation via inoculation in BHK21, inoculation in suckling baby mice and complement fixation test then formulate vaccine using different methods of inactivation then applying the quality control tests to evaluate each formulated vaccine.

RESULTS

The effect of heat, gamma radiation, and UV on the ability of replication of FMDV "O/pan Asia, A/Iran05, and SAT-2/2012" was determined through BHK cell line passage. Each of the 9 virus aliquots titer 10(8) TCID50 (3 for each strain) were exposed to 37, 57, and 77°C for 15, 30, and 45 min. Similarly, another 15 aliquots (5 for each strain) contain 1 mm depth of the exposed samples in petri-dish was exposed to UV light (252.7 nm wavelength: One foot distance) for 15, 30, 45, 60, and 65 min. Different doses of gamma radiation (10, 20, 25, 30, 35, 40, 45, 50, 55, and 60 KGy) were applied in a dose rate 0.551 Gy/s for each strain and repeated 6 times for each dose. FMDV (O/pan Asia, A/Iran05, and SAT-2/2012) were inactivated when exposed to heat ≥57°C for 15 min. The UV inactivation of FMDV (O/pan Asia and SAT-2) was obtained within 60 min and 65 min for type A/Iran05. The ideal dose for inactivation of FMDV (O/pan Asia, A/Iran05, and SAT-2/2012) with gamma radiation were 55-60 and 45 kGy, respectively. Inactivation of FMDV with binary was 20, 24 and 16 hr for O/pan Asia, A/Iran05, and SAT-2/2012, respectively while inactivation by (BEI+FA) was determined after 18, 19 and 11 hr for O/pan-Asia, A/Iran 05, and SAT-2/2012, respectively. The antigenicity of control virus before inactivation was 1/32, it was not changed after inactivation in case of gamma radiation and (BEI+FA) and slightly decrease to 1/16 in case of binary and declined to 1/2, 1/4 in case of heat and UV inactivation, respectively. The immune response induced by inactivated FMD vaccines by gamma radiation and (BEI+FA) lasted to 9 months post-vaccination, while the binary only still up to 8 months post-vaccination but heat and UV-inactivated vaccines were not effective.

CONCLUSION

Gamma radiation could be considered a good new inactivator inducing the same results of inactivated vaccine by binary with formaldehyde (BEI+FA).

Characterization and control of surfactant-mediated Norovirus interactions

Understanding of the colloidal interactions of Norovirus particles in aqueous medium could provide insights on the origins of the notorious stability and infectivity of these widespread viral agents. We characterized the effects of solution pH and surfactant type and concentration on the aggregation, dispersion, and disassembly of Norovirus virus-like particles (VLPs) using dynamic light scattering, electrophoretic light scattering, and transmission electron microscopy. Owing to net negative surface charge of the VLPs at neutral pH, low concentrations of cationic surfactant tend to aggregate the VLPs, whereas low concentrations of anionic surfactant tend to disperse the particles. Increasing the concentration of these surfactants beyond their critical micelle concentration leads to virus capsid disassembly and breakdown of aggregates. Non-ionic surfactants, however, had little effect on virus interactions and likely stabilized them additionally in suspension. The data were interpreted on the basis of simple models for surfactant binding and re-charging of the virus capsid. We used zeta potential data to characterize virus surface charge and interpret the mechanisms behind these demonstrated surfactant-virus interactions. The fundamental understanding and control of these interactions will aid in practical formulations for virus inactivation and removal from contaminated surfaces.

Fate of Foodborne Viruses in the "Farm to Fork" Chain of Fresh Produce

Norovirus (NoV) and hepatitis A virus (HAV) are the most important foodborne viruses. Fresh produce has been identified as an important vehicle for their transmission. In order to supply a basis to identify possible prevention and control strategies, this review intends to demonstrate the fate of foodborne viruses in the farm to fork chain of fresh produce, which include the introduction routes (contamination sources), the viral survival abilities at different stages, and the reactions of foodborne viruses towards the treatments used in food processing of fresh produce. In general, the preharvest contamination comes mainly from soli fertilizer or irrigation water, while the harvest and postharvest contaminations come mainly from food handlers, which can be both symptomatic and asymptomatic. Foodborne viruses show high stabilities in all the stages of fresh produce production and processing. Low-temperature storage and other currently used preservation techniques, as well as washing by water have shown limited added value for reducing the virus load on fresh produce. Chemical sanitizers, although with limitations, are strongly recommended to be applied in the wash water in order to minimize cross-contamination. Alternatively, radiation strategies have shown promising inactivating effects on foodborne viruses. For high-pressure processing and thermal treatment, efforts have to be made on setting up treatment parameters to induce sufficient viral inactivation within a food matrix and to protect the sensory and nutritional qualities of fresh produce to the largest extent.

A Membrane-Based Electro-Separation Method (MBES) for Sample Clean-Up and Norovirus Concentration

Noroviruses are the leading cause of acute gastroenteritis and foodborne illnesses in the United States. Enhanced methods for detecting noroviruses in food matrices are needed as current methods are complex, labor intensive and insensitive, often resulting in inhibition of downstream molecular detection and inefficient recovery. Membrane-based electro-separation (MBES) is a technique to exchange charged particles through a size-specific dialysis membrane from one solution to another using electric current as the driving force. Norovirus has a net negative surface charge in a neutrally buffered environment, so when placed in an electric field, it moves towards the anode. It can then be separated from the cathodic compartment where the sample is placed and then collected in the anodic compartment for downstream detection. In this study, a MBES-based system was designed, developed and evaluated for concentrating and recovering murine norovirus (MNV-1) from phosphate buffer. As high as 30.8% MNV-1 migrated from the 3.5 ml sample chamber to the 1.5 ml collection chamber across a 1 μm separation membrane when 20 V was applied for 30 min using 20 mM sodium phosphate with 0.01% SDS (pH 7.5) as the electrolyte. In optimization of the method, weak applied voltage (20 V), moderate duration (30 min), and low ionic strength electrolytes with SDS addition were needed to increase virus movement efficacy. The electric field strength of the system was the key factor to enhance virus movement, which could only be improved by shortening the electrodes distance, instead of increasing system applied voltage because of virus stability. This study successfully demonstrated the norovirus mobility in an electric field and migration across a size-specific membrane barrier in sodium phosphate electrolyte. With further modification and validation in food matrixes, a novel, quick, and cost-effective sample clean-up technique might be developed to separate norovirus particles from food matrices by electric force.

Antiviral Activity of Gold/Copper Sulfide Core/Shell Nanoparticles against Human Norovirus Virus-Like Particles

Human norovirus is a leading cause of acute gastroenteritis worldwide in a plethora of residential and commercial settings, including restaurants, schools, and hospitals. Methods for easily detecting the virus and for treating and preventing infection are critical to stopping norovirus outbreaks, and inactivation via nanoparticles (NPs) is a more universal and attractive alternative to other physical and chemical approaches. Using norovirus GI.1 (Norwalk) virus-like particles (VLPs) as a model viral system, this study characterized the antiviral activity of Au/CuS core/shell nanoparticles (NPs) against GI.1 VLPs for the rapid inactivation of HuNoV. Inactivation of VLPs (GI.1) by Au/CuS NPs evaluated using an absorbance-based ELISA indicated that treatment with 0.083 μM NPs for 10 min inactivated ~50% VLPs in a 0.37 μg/ml VLP solution and 0.83 μM NPs for 10 min completely inactivated the VLPs. Increasing nanoparticle concentration and/or VLP-NP contact time significantly increased the virucidal efficacy of Au/CuS NPs. Changes to the VLP particle morphology, size, and capsid protein were characterized using dynamic light scattering, transmission electron microscopy, and Western blot analysis. The strategy reported here provides the first reported proof-of-concept Au/CuS NPs-based virucide for rapidly inactivating human norovirus.

Thermal Inactivation Kinetics of Human Norovirus Surrogates and Hepatitis A Virus in Turkey Deli Meat

Human noroviruses (HNoV) and hepatitis A virus (HAV) have been implicated in outbreaks linked to the consumption of presliced ready-to-eat deli meats. The objectives of this research were to determine the thermal inactivation kinetics of HNoV surrogates (murine norovirus 1 [MNV-1] and feline calicivirus strain F9 [FCV-F9]) and HAV in turkey deli meat, compare first-order and Weibull models to describe the data, and calculate Arrhenius activation energy values for each model. The D (decimal reduction time) values in the temperature range of 50 to 72°C calculated from the first-order model were 0.1 ± 0.0 to 9.9 ± 3.9 min for FCV-F9, 0.2 ± 0.0 to 21.0 ± 0.8 min for MNV-1, and 1.0 ± 0.1 to 42.0 ± 5.6 min for HAV. Using the Weibull model, the tD = 1 (time to destroy 1 log) values for FCV-F9, MNV-1, and HAV at the same temperatures ranged from 0.1 ± 0.0 to 11.9 ± 5.1 min, from 0.3 ± 0.1 to 17.8 ± 1.8 min, and from 0.6 ± 0.3 to 25.9 ± 3.7 min, respectively. The z (thermal resistance) values for FCV-F9, MNV-1, and HAV were 11.3 ± 2.1°C, 11.0 ± 1.6°C, and 13.4 ± 2.6°C, respectively, using the Weibull model. The z values using the first-order model were 11.9 ± 1.0°C, 10.9 ± 1.3°C, and 12.8 ± 1.7°C for FCV-F9, MNV-1, and HAV, respectively. For the Weibull model, estimated activation energies for FCV-F9, MNV-1, and HAV were 214 ± 28, 242 ± 36, and 154 ± 19 kJ/mole, respectively, while the calculated activation energies for the first-order model were 181 ± 16, 196 ± 5, and 167 ± 9 kJ/mole, respectively. Precise information on the thermal inactivation of HNoV surrogates and HAV in turkey deli meat was generated. This provided calculations of parameters for more-reliable thermal processes to inactivate viruses in contaminated presliced ready-to-eat deli meats and thus to reduce the risk of foodborne illness outbreaks.

Inactivation of norovirus and surrogates by natural phytochemicals and bioactive substances

Human norovirus is the leading cause of sporadic gastroenteritis, which is responsible for more than 90% of all nonbacterial gastroenteritis outbreaks. While norovirus infections typically cause mild and self-limiting symptoms lasting 24-48 h, chronic persistent infections can cause severe symptoms. Although recent advances have been made in understanding the molecular characteristics of norovirus infection, no norovirus-specific antiviral drugs, or vaccines are available. Conventional intervention methods used to inactivate norovirus, such as treatment with disinfecting agents (e.g. ethanol, hypochlorite, and quaternary ammonium formulations), have shown a lack of efficacy against human norovirus when they are applied to foods and in food preparation processes. Therefore, alternative antiviral or inactivating agents such as phytochemicals have received attention as potential norovirus inhibitors due to their relatively low toxicity and lack of side effects, which allows them to be prepared as food-safe formulations. Evidence from studies using viral surrogates suggests that numerous phytochemicals and foods containing flavonoids and polyphenols have anti-norovirus activity, and future studies will be necessary to confirm the effectiveness of such compounds against human norovirus and the molecular mechanisms through which they produce antiviral effects.

Determination of thermal inactivation kinetics of hepatitis A virus in blue mussel (Mytilus edulis) homogenate

Hepatitis A virus (HAV) is a food-borne enteric virus responsible for outbreaks of hepatitis associated with shellfish consumption. The objectives of this study were to determine the thermal inactivation behavior of HAV in blue mussels, to compare the first-order and Weibull models to describe the data, to calculate Arrhenius activation energy for each model, and to evaluate model efficiency by using selected statistical criteria. The times required to reduce the population by 1 log cycle (D-values) calculated from the first-order model (50 to 72°C) ranged from 1.07 to 54.17 min for HAV. Using the Weibull model, the times required to destroy 1 log unit (tD = 1) of HAV at the same temperatures were 1.57 to 37.91 min. At 72°C, the treatment times required to achieve a 6-log reduction were 7.49 min for the first-order model and 8.47 min for the Weibull model. The z-values (changes in temperature required for a 90% change in the log D-values) calculated for HAV were 15.88 ± 3.97°C (R(2), 0.94) with the Weibull model and 12.97 ± 0.59°C (R(2), 0.93) with the first-order model. The calculated activation energies for the first-order model and the Weibull model were 165 and 153 kJ/mol, respectively. The results revealed that the Weibull model was more appropriate for representing the thermal inactivation behavior of HAV in blue mussels. Correct understanding of the thermal inactivation behavior of HAV could allow precise determination of the thermal process conditions to prevent food-borne viral outbreaks associated with the consumption of contaminated mussels.