Conducting persistence studies of infectious severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on environmental surfaces may require a biosafety level 3 (BSL-3) laboratory. We aimed to compare the environmental persistence of BSL-2 level human coronaviruses (229E, NL63, and OC43) and bovine coronavirus (BoCoV) with three SARS-CoV-2 variants (WA-1, Delta, and Omicron). OC43 (1.8 TCID(50)/mL) and BoCoV (1.0 TCID(50)/mL) had lower detection thresholds in cell culture assays compared to 229E (150 TCID(50)/mL) and NL63 (2,670 TCID(50)/mL) and were used for persistence tests at room temperature. Viable OC43 became undetectable (>5.2log(10)) after 48 hours on stainless steel and plastic coupons but exhibited extended persistence up to 72 hours on touchscreen glass coupons. In contrast, BoCoV remained viable for up to 120 hours with <1.8 log(10) infectivity loss. Both OC43 and BoCoV showed a reduction of >5 log(10) on vinyl coupons after 48 hours. On stainless steel coupons, the viability of all three SARS-CoV-2 variants became undetectable (>2.3 log(10) reduction) after 48 hours, with minor differences in reduction levels at 24 hours, whereas on touchscreen glass coupons, the viable virus could be detected for up to 48 hours for WA-1 and Omicron and 72 hours for the Delta variant. Regardless of coupon or virus type, viral RNA titers increased <4.5 Ct values after 120 hours. Our data demonstrate distinct persistence characteristics between BoCoV and OC43, with neither fully mimicking SARS-CoV-2 variants. This variability along with the impact of surface types on viral persistence underscores the need for caution when using these viruses as surrogates for SARS-CoV-2.IMPORTANCEIn this study, we evaluated three human seasonal coronaviruses (OC43, NL63, and 229E) and one bovine coronavirus (BoCoV) as potential surrogate viruses for SARS-CoV-2. Our data suggest that among the four surrogate viruses tested, OC43 and BoCoV were the most promising candidates due to their assay sensitivity, ease of handling, and high genetic similarity to SARS-CoV-2. However, neither BoCoV nor OC43 fully mimicked the environmental persistence characteristics of SARS-CoV-2 variants highlighting the potential limitations of using surrogate viruses.

CrAssphages are human gut bacteriophages with potential use as an indicator of human fecal contamination in water and other environmental systems. We determined the prevalence and abundance of crAssphages in water, food, and fecal samples and compared these estimates with the prevalence of norovirus. Samples were tested using two crAssphage-specific qPCR assays (CPQ056 and TN201-203) and for norovirus using TaqMan realtime RT-PCR. CrAssphage was detected in 40% of human fecal specimens, 61% of irrigation water samples, 58.5% of stream water samples, and 68.5% of fresh leafy greens samples. Interestingly, across all sample categories, crAssphage concentrations were 2-3 log10 higher than norovirus concentrations. The correlation of detection of crAssphage and norovirus was significant for the irrigation water samples (r = 0.74, p = 7.4e-06). Sequences obtained from crAssphage positive samples from human fecal and stream water samples phylogenetically clustered with genotype I crAssphages, whereas sequences derived from irrigation water samples clustered differently from other genotypes. Our data show that crAssphages were prevalent in norovirus-positive water samples and in fresh leafy green samples, there was a strong correlation between the presence of crAssphage and norovirus. CrAssphage genomic copies were consistently higher than norovirus copies in all sample types. Overall, our findings suggest that crAssphages could be used as reliable indicators to monitor fecal-borne virus contamination within the food safety chain.

While the COVID-19 pandemic has had a detrimental impact on many businesses worldwide, essential businesses, such as grocery stores, continued to operate despite potential disease transmission. Although the principal mode by which people are infected with SARS-CoV-2, the virus that causes COVID-19, is through exposure to respiratory droplets and very small particles carrying infectious virus, contaminated surfaces might play a role in transmission. We collected swab samples from frequently touched surfaces, including grocery carts, touchscreen monitors, credit card keypads, pharmacy counters, self-service food utensils, and refrigerator and freezer handles, in two metro-Atlanta grocery stores over the course of two sampling events in March 2021. Of the 260 swab samples collected, 6 (2.3%) samples were positive for SARS-CoV-2 RNA by reverse transcriptase quantitative polymerase chain reaction. Positive samples were collected from pharmacy (12.0% [3/25] samples), refrigerator/freezer aisles (2.5% [1/39] samples), and self-service food court (5.0% [2/40] samples) areas. Table/counter edge and underside surfaces represented 33% (2/6) of positive samples. These data suggest that risk of exposure to SARS-CoV-2 from frequently touched surfaces in grocery store settings is likely low; however, more frequent cleaning of surfaces in pharmacy and self-service food courts might be warranted.

While risk of fomite transmission of SARS-CoV-2 is considered low, there is limited environmental data within households. This January-April 2021 investigation describes frequency and types of surfaces positive for SARS-CoV-2 by real-time reverse transcription polymerase chain reaction (RT-PCR) among residences with ≥1 SARS-CoV-2 infection, and associations of household characteristics with surface RT-PCR and viable virus positivity. Of 1232 samples from 124 households, 27.8% (n = 342) were RT-PCR positive with nightstands (44.1%) and pillows (40.9%) most frequently positive. SARS-CoV-2 lineage, documented household transmission, greater number of infected persons, shorter interval between illness onset and sampling, total household symptoms, proportion of infected persons ≤12 years old, and persons exhibiting upper respiratory symptoms or diarrhea were associated with more positive surfaces. Viable virus was isolated from 0.2% (n = 3 samples from one household) of all samples. This investigation suggests that while SARS-CoV-2 on surfaces is common, fomite transmission risk in households is low.

AIMS: To determine the efficacy of a panel of nine EPA-registered disinfectants against two human norovirus (HuNoV) surrogates [feline calicivirus (FCV) and Tulane virus (TuV)] and Clostridioides difficile endospores. METHODS AND RESULTS: Nine EPA-registered products, five of which contained H(2) O(2) as active ingredient, were tested against infectious FCV, TuV, and C. difficile endospores using two ASTM methods, a suspension and carrier test. Efficacy claims against FCV were confirmed for 8 of 9 products. The most efficacious product containing H(2) O(2) as ingredient, achieved a >5.1 log reduction of FCV and >3.1 log reduction of TuV after 5 min, and >6.0 log reduction of C. difficile endospores after 10 min. Of the five products containing H(2) O(2) , no strong correlation (R(2) =0.25, p=0.03) was observed between disinfection efficacy and H(2) O(2) concentration. Addition of 0.025% ferrous sulfate to 1% H(2) O(2) solution improved efficacy against FCV, TuV, and C. difficile. CONCLUSION: Disinfectants containing H(2) O(2) are the most efficacious disinfection products against FCV, TuV and C. difficile endospores. Product formulation, rather than the concentration of H(2) O(2) in a product, impacts the efficacy of a disinfection product. SIGNIFICANCE AND IMPACT OF STUDY: H(2) O(2) -based disinfectants are efficacious against surrogate viruses for HuNoV and C. difficile endospores.

BACKGROUND: Norovirus and C. difficile are associated with diarrheal illnesses and deaths in long-term care (LTC) facilities and can be transmitted by contaminated environmental surfaces. Hygienic monitoring tools such as adenosine triphosphate (ATP) bioluminescence and indicators of fecal contamination can help to identify LTC facility surfaces with cleaning deficiencies. METHODS: High-touch surfaces in 11 LTC facilities were swabbed and tested for contamination by norovirus, a fecal indicator virus, crAssphage, and ATP which detects organic debris. High levels of contamination were defined as log ATP relative light unit values or crAssphage log genomic copy values in the 75th percentile of values obtained from each facility. RESULTS: Over 90% of surfaces tested positive for crAssphage or gave failing ATP scores. Norovirus contamination was not detected. Handrails, equipment controls, and patient beds were 4 times more likely than other surfaces or locations to have high levels of crAssphage. Patient bed handrails and tables and chairs in patient lounges had high levels of both ATP and crAssphage. CONCLUSIONS: Surfaces with high levels of ATP and crAssphage were identified. Quantifying levels of contamination longitudinally and before and after cleaning might enhance infection prevention and control procedures for reducing diarrheal illnesses in LTC facilities.

SARS-CoV-2 transmission from contaminated surfaces, or fomites, has been a concern during the COVID-19 pandemic. Households have been important sites of transmission throughout the COVID-19 pandemic, but there is limited information on SARS-CoV-2 contamination of surfaces in these settings. We describe environmental detection of SARS-CoV-2 in households of persons with COVID-19 to better characterize the potential risks of fomite transmission. Ten households with ≥1 person with laboratory-confirmed COVID-19 and with ≥2 members total were enrolled in Utah, U.S.A. Nasopharyngeal and anterior nasal swabs were collected from members and tested for the presence of SARS-CoV-2 by RT-PCR. Fifteen surfaces were sampled in each household and tested for presence and viability of SARS-CoV-2. SARS-CoV-2 RNA was detected in 23 (15%) of 150 environmental swab samples, most frequently on nightstands (4/6; 67%), pillows (4/23; 17%), and light switches (3/21; 14%). Viable SARS-CoV-2 was cultured from one sample. All households with SARS-CoV-2-positive surfaces had ≥1 person who first tested positive for SARS-CoV-2 ≤ 6 days prior to environmental sampling. SARS-CoV-2 surface contamination occurred early in the course of infection when respiratory transmission is most likely, notably on surfaces in close, prolonged contact with persons with COVID-19. While fomite transmission might be possible, risk is low.

CrAssphage is a recently discovered human gut-associated bacteriophage. To validate the potential use of crAssphage for detecting human fecal contamination on environmental surfaces and hands, we tested stool samples (n = 60), hand samples (n = 30), and environmental swab samples (n = 201) from 17 norovirus outbreaks for crAssphage by real-time PCR. In addition, we tested stool samples from healthy persons (n = 173), respiratory samples (n = 113), and animal fecal specimens (n = 68) and further sequenced positive samples. Overall, we detected crAssphage in 71.4% of outbreak stool samples, 48%-68.5% of stool samples from healthy persons, 56.2% of environmental swabs, and 60% of hand rinse samples, but not in human respiratory samples or animal fecal samples. CrAssphage sequences could be grouped into 2 major genetic clusters. Our data suggest that crAssphage could be used to detect human fecal contamination on environmental surfaces and hands.

We examined norovirus contamination on hands of ill patients during 12 norovirus outbreaks in 12 long-term care facilities (LTCFs). The higher frequency and norovirus titers on hands of residents compared to hands of heathcare workers highlights the importance of adhering to appropriate hand hygiene practices during norovirus outbreaks in LTCFs. Infect Control Hosp Epidemiol 2018;1-3.

The complete coding sequences of three melon necrotic spot viruses (MNSVs) were obtained from viral metagenomics of stool samples from patients with acute gastroenteritis. These genomes were most similar to Spanish strains sequenced in 2003 and a novel MNSV watermelon strain in 2014.

Human noroviruses are a leading cause of epidemic and sporadic gastroenteritis worldwide. Because most infections are either spread directly via the person-to-person route or indirectly through environmental surfaces or food, contaminated fomites and inanimate surfaces are important vehicles for the spread of the virus during norovirus outbreaks. We developed and evaluated a protocol using macrofoam swabs for the detection and typing of human noroviruses from hard surfaces. Compared with fiber-tipped swabs or antistatic wipes, macrofoam swabs allow virus recovery (range 1.2-33.6%) from toilet seat surfaces of up to 700 cm2. The protocol includes steps for the extraction of the virus from the swabs and further concentration of the viral RNA using spin columns. In total, 127 (58.5%) of 217 swab samples that had been collected from surfaces in cruise ships and long-term care facilities where norovirus gastroenteritis had been reported tested positive for GII norovirus by RT-qPCR. Of these 29 (22.8%) could be successfully genotyped. In conclusion, detection of norovirus on environmental surfaces using the protocol we developed may assist in determining the level of environmental contamination during outbreaks as well as detection of virus when clinical samples are not available; it may also facilitate monitoring of effectiveness of remediation strategies.

Alcohol-based hand sanitizers are widely used to disinfect hands to prevent the spread of pathogens including noroviruses. Alcohols inactivate norovirus by destruction of the viral capsid, resulting in the leakage of viral RNA (virolysis). Since conflicting results have been reported on the susceptibility of human noroviruses against alcohols, we exposed a panel of 30 human norovirus strains (14 GI and 16 GII strains) to different concentrations (50%, 70%, 90%) of ethanol and isopropanol and tested the viral RNA titer by RT-qPCR. Viral RNA titers of 10 (71.4%), 14 (100%), 3 (21.4%) and 7 (50%) of the 14 GI strains were reduced by > 1 log10 RNA copies/ml after exposure to 70% and 90% ethanol, and 70% and 90% isopropanol, respectively. RNA titers of 6 of the 7 non-GII 4 strains remained unaffected after alcohol exposure. Compared to GII strains, GI strains were more susceptible to ethanol than to isopropanol. At 90%, both alcohols reduced RNA titers of 8 of the 9 GII.4 strains by ≥ 1 log10 RNA copies/ml. After exposure to 70% ethanol, RNA titers of GII.4 Den Haag and Sydney strains decreased by ≥ 1.9 log10, whereas RNA reductions for GII.4 New Orleans strains were < 0.5 log10. To explain these differences, we sequenced the complete capsid gene of the 9 GII.4 strains and identified 17 amino acid substitutions in the P2 region among the 3 GII.4 variant viruses. When comparing with an additional set of 200 GII.4 VP1 sequences, only S310 and P396 were present in all GII.4 New Orleans viruses but not in the ethanol-sensitive GII.4 Sydney and GII.4 Den Haag viruses Our data demonstrate that alcohol susceptibility patterns between different norovirus genotypes vary widely and that virolysis data for a single strain or genotype are not representative for all noroviruses.

Inanimate surfaces are regarded as key vehicles for the spread of human norovirus during outbreaks. The ISO-method 15216 describes the use of cotton swabs for environmental sampling from food surfaces and fomites for the detection of norovirus GI and GII. We evaluated the effect of virus drying times (1, 8, 24, 48 h), different swab materials (cotton, polyester, rayon, macrofoam and antistatic wipe), different surfaces (stainless steel and toilet seat) and swab surface area (25.8 cm2 to 645.0 cm2 on the recovery of human norovirus. Compared to the other swabs, macrofoam had the highest recovery of norovirus from surfaces up to 645cm2. Recovery ranged from 2.2 -36.0% for virus seeded on stainless steel coupons (645.0 cm2) to 1.2 - 33.6% from toilet seat surface (700 cm2) with a detection limit of 3.5 and 4.0 log10 RNA copies. We used macrofoam swabs to collect environmental samples from several case cabins and common areas from a cruise ship where passengers had reported viral gastroenteritis symptoms. Seventeen (18.5%) of 92 samples tested positive for norovirus GII and 4 samples could be sequenced and had identical GII.1 sequences. The viral load of the swab samples from the cabins of the sick passengers ranged from 80 to 31,217 RNA copies compared 16 to 113 RNA copies for the swab samples from public spaces. In conclusion, our swab protocol for norovirus may be a useful tool in addition to testing of clinical specimens for outbreak investigations when no clinical samples are available to confirm the etiology.

Previous studies have shown bismuth subsalicylate (BSS) has antimicrobial properties, but few studies have addressed the mechanism of action. Furthermore, following BSS ingestion other bismuth salts form throughout the gastrointestinal tract including bismuth oxychloride (BiOCl) that also act upon enteric pathogens. To further understand the antimicrobial activity of bismuth in infectious diarrhea, the antimicrobial effect of BSS and BiOCl on Clostridium difficile, Salmonella, Shigella, Shiga toxin-producing Escherichia coli strains and norovirus (NoV) were measured. Bacterial enteric pathogens in pure culture or in human fecal material were exposed to 35mg/ml BSS or BiOCl with or without a vehicle suspension. BSS and BiOCl treated samples were quantified and visualized by transmission electron microscopy. To measure the effect on NoV, reduction of infectious murine NoV (MNV), a surrogate for human NoV, and Norwalk virus RNA levels were measured by viral plaque assay and RT-qPCR, respectively. BSS and BiOCl reduced bacterial growth by 3-9 logs in all strains with majority resulting in populations of <10 cfu/ml within 24 h. Similar results were found when fecal material was included. Microscopy images detected bismuth on bacterial membranes and within the bacterial organisms at 30 min post-treatment. At 8.8mg/ml BSS and BiOCl reduced infectivity of MNV significantly by 2.7 and 2.0 log after 24 h of exposure. In addition, both BSS and BiOCl slightly reduced the level of Norwalk replicon-bearing cells suggesting that bismuth may inhibit NoV in vivo. Collectively, our results confirm and build on existing data that BSS has antimicrobial properties against a wide-range of diarrhea-causing pathogens.

We evaluated the virucidal efficacy of light-activated fluorinated TiO2 surface coatings on human norovirus and several surrogates (bacteriophage MS2, feline calcivirus (FCV), and murine norovirus (MNV)). Inactivation of viruses on surfaces exposed to a common fluorescent lamp was monitored and the effects of UVA intensity, temperature, and fluoride content were assessed. Destruction of RNA and capsid oxidation were evaluated for human norovirus inocula on the F-TiO2 surfaces, while contact with the F-TiO2 surface and exposure to residual UVA radiation of 10muWcm-2 for 60min resulted in infectivity reductions for the norovirus surrogates of 2-3 log10. Infectivity reductions on pristine TiO2 surfaces in identical conditions were over 2 orders of magnitude lower. Under realistic room lighting conditions, MS2 infectivity declined below the lower detection limit after 12h. Reductions in RNA were generally low, with the exception of GII.4, while capsid protein oxidation likely played a larger role in infectivity loss. Inactivation of norovirus surrogates occurred significantly faster on F-TiO2 compared to pristine TiO2 surfaces. The material demonstrated antiviral action against human norovirus surrogates and was shown to effectively inhibit MS2 when exposed to residual UVA present in fluorescent room lighting conditions in a laboratory setting.

Human norovirus is the leading cause of epidemic and sporadic acute gastroenteritis. Since no cell culture method for human norovirus exists, cultivable surrogate viruses (CSV) including feline calicivirus (FCV), murine norovirus (MNV), porcine enteric calicivirus (PEC) and Tulane virus (TuV) have been used to study the response to inactivation and disinfection methods. We compared the infectivity reduction of CSV and Aichi virus (AiV) by extreme pH, 56 degrees C heating, alcohols, chlorine on surfaces, and high hydrostatic pressure (HHP) using the same matrix and identical test parameters for all viruses, and compared with reduction of human norovirus RNA. At pH 2 FCV was inactivated by 6 log10 whereas MNV, TuV and AiV were resistant. All CSV were completely inactivated at 56 degrees C within 20 min. MNV was inactivated 5 log10 by alcohols compared to 2 and 3 log10 for FCV and PEC, respectively. TuV and AiV were relatively insensitive to alcohols. FCV was reduced 5 log10 by 1,000 ppm chlorine compared to 1 log10 for the other CSV. All CSV except FCV dried on stainless steel surfaces were insensitive to 200 ppm chlorine. HHP completely inactivated FCV, MNV, and PEC at ≥300 megapascal (MPa), TuV at 600 MPa while AiV was completely resistant up to 800 MPa. By RT-qPCR, genogroup (G)I norovirus was more sensitive than GII norovirus to alcohols, chlorine, and HHP. Although inactivation profiles were variable for each treatment, overall TuV and MNV were the most resistant CSV and therefore are best candidates to study public health outcomes of norovirus infections.

Norovirus infections are notoriously difficult to prevent and control due to their low infectious dose, high shedding titer, and environmental stability. The virus can spread through multiple transmission routes of which person-to-person and foodborne are the most important. Recent advances in molecular diagnostics, have helped to establish norovirus as the most common cause of sporadic gastroenteritis and most common cause of outbreaks of acute gastroenteritis across all ages. In this paper, we review the epidemiology and virology of noroviruses as well as prevention and control guidelines with a focus on the principles of disinfection and decontamination; Outbreak management relies on sound infection control principles including hand hygiene, limiting exposure to infectious individuals, and thorough environmental decontamination. Ideally, all infection control recommendations would rely on empirical evidence, but a number of challenges, including the inability to culture norovirus in the laboratory and the challenges of outbreak management in complex environments, has made it difficult to garner clear evidence of efficacy in certain areas of infection control. New experimental data on cultivable surrogates for human norovirus on the environmental survivability and relative resistance to commonly used disinfectants, are providing new insights in further refining disinfection practices. Finally, clinical trials are underway to evaluate the efficacy of vaccines which may shift the current infection control principles to more targeted interventions. This article is protected by copyright. All rights reserved.

The advent of molecular techniques and their increasingly widespread use in public health laboratories and research studies has transformed the understanding of the burden of norovirus. Norovirus is the most common cause of community-acquired diarrheal disease across all ages, the most common cause of outbreaks of gastroenteritis, and the most common cause of foodborne disease in the United States. They are a diverse group of single-stranded RNA viruses that are highly infectious and stable in the environment; both symptomatic and asymptomatic infections are common. Through shedding in feces and vomit, norovirus can be transmitted directly through an array of routes: person-to-person, food or the environment. The relative importance of environmental transmission of virus is yet to be fully quantified but is likely to be substantial and is an important feature that complicates control. (2011 Elsevier B.V. All rights reserved.)

Noroviruses are the most common cause of epidemic gastroenteritis, responsible for at least 50% of all gastroenteritis outbreaks worldwide, and a major cause of foodborne illness. In the United States, approximately 21 million illnesses attributable to norovirus are estimated to occur annually. Since 2001, when the most recent norovirus recommendations were published (CDC. "Norwalk-like viruses." Public health consequences and outbreak management. MMWR 2001;50[No. RR-9]), substantial advances have been made in norovirus epidemiology, immunology, diagnostic methods, and infection control. As molecular diagnostic techniques have improved in performance and become more widely available, detection and reporting of norovirus outbreaks have increased. Although the inability to culture human noroviruses in vitro has hampered progress, assessment of the performance of disinfectants has been facilitated by the discovery of new, cultivable surrogates for human noroviruses. In addition, the periodic emergence of epidemic strains (from genogroup II type 4, GII.4) and outbreaks in specific populations (e.g., the elderly in nursing homes) have been characterized. This report reviews these recent advances and provides guidelines for outbreak management and disease prevention. These recommendations are intended for use by public health professionals investigating outbreaks of acute gastroenteritis, including state and local health authorities, as well as academic and research institutions.

Free chlorine as hypochlorite is recommended to decontaminate fecally contaminated surfaces to control human norovirus (NoV). We evaluated the efficacy of sodium hypochlorite to decontaminate GII.4 NoV and three surrogates of human NoVs, feline calicivirus (FCV), murine norovirus (MNV), and coliphage MS2, on a fecally soiled stainless steel surface. Reduction of infectivity of FCV, MNV, and MS2 was measured by plaque assay and the decline of genomic copy numbers of GII.4 NoV by reverse transcriptase-polymerase chain reaction. Sodium hypochlorite solution at 5000 ppm could inactivate FCV by 3 log(10) plaque forming units after approximately 1.9 minutes of contact time, but required longer exposure times of 3.2 and 4.5 minutes to reduce MNV and MS2 by 3 log(10), respectively. However, detection of viral RNA by reverse transcriptase-polymerase chain reaction assay may not be reliable to estimate the effectiveness of sodium hypochlorite against human NoV. Of three NoV surrogates, FCV is not the most resistant of the virus tested for inactivation by hypochlorite and thus is not the worst-case model for estimating NoV inactivation. Although the use of 5000 ppm of hypochlorite for fecally soiled surfaces is effective, it may require longer exposure times of ≥3 minutes to control NoVs. Surface precleaning before hypochlorite disinfection is recommended to initially reduce the fecal organic load for better virus inactivation and should be a part of the environmental hygiene response measures during an NoV outbreak or where NoV fecal contamination of environmental surfaces is likely or suspected to be present.

AIMS: To determine inactivation profiles of three human norovirus (NoV) surrogate viruses and coliphage MS2 by ultraviolet (UV) irradiation and the protective effect of cell association on UV inactivation. METHODS AND RESULTS: The inactivation rate for cell-free virus or intracellular echovirus 12 was determined by exposure to 254-nm UV light at fluence up to 100 mJ cm(-2) . The infectivity of murine norovirus (MNV), feline calicivirus (FCV) and echovirus 12 was determined by cell culture infectivity in susceptible host cell lines, and MS2 infectivity was plaque assayed on Escherichia coli host cells. The UV fluencies to achieve 4-log(10) inactivation were 25, 29, 30 and 70 (mJ cm(-2) ) for cell-free FCV, MNV, echovirus 12 and MS2, respectively. However, a UV fluence of 85 mJ cm(-2) was needed to inactivate intracellular echovirus 12 by 4 log(10) . CONCLUSIONS: Murine norovirus and echoviruses 12 are more conservative surrogates than FCV to predict the UV inactivation response of human NoV. Intracellular echovirus 12 was 2.8-fold more resistant to UV irradiation than cell-free one. SIGNIFICANCE AND IMPACT OF THE STUDY: Variation in UV susceptibilities among NoV surrogate viruses and a likely protective effect of cell association on virus susceptibility to UV irradiation should be considered for effective control of human NoV in water.

Contaminated hands or inanimate surfaces can act as a source of infection during outbreaks of human norovirus infection. We evaluated the virucidal efficacy of seven hand sanitizers containing various active ingredients, such as ethanol, triclosan, and chlorhexidine, and compared their effectiveness against feline calicivirus (FCV), murine norovirus (MNV), and a GII.4 norovirus fecal extract. We also tested the efficacy of 50, 70, and 90% of ethanol and isopropanol. Reduction of viral infectivity was measured by plaque assay, and the number of genomic copies was determined with a TaqMan real-time reverse transcription PCR assay. Based on the results of a quantitative suspension test, only one ethanol-based product (72% ethanol, pH 2.9) and one triclosan-based product (0.1% triclosan, pH 3.0) reduced the infectivity of both MNV and FCV (by >2.6 and ≥3.4 log units, respectively). Four of the seven products were effective against either MNV or FCV, whereas chlorhexidine was ineffective against both viruses. For these hand sanitizers, no correlation was found between reduced infectivity and decline of viral RNA. Ethanol and isopropanol concentrations ≥70% reduced the infectivity of MNV by ≥2.6 log units, whereas 50 and 70% ethanol reduced the infectivity of FCV by ≥2.2 log units after exposure for 5 min. The susceptibility of FCV to low pH and the relative high susceptibility of MNV to alcohols suggest that both surrogate viruses should be considered for in vitro testing of hand sanitizers.