Community Transmission of SARS-CoV-2 by Surfaces: Risks and Risk Reduction Strategies

Quantifying fomite hotspots and targeted hygiene impacts in a hotel lobby

Environmental surfaces in public settings serve as reservoirs for microbial pathogens, including norovirus, rhinovirus, and adenovirus, which can persist and spread through hand-to-fomite contact. Despite limited evidence of SARS-CoV-2 fomite transmission, hygiene protocols were widely intensified during the pandemic. This study evaluates viral spread and infection risks in a hotel lobby and assesses the efficacy of a Targeted Hygiene intervention designed to reduce contamination while minimizing excessive chemical use. A viral tracer study, using bacteriophage Phi X174, and human behavior observations were utilized to monitor surface contamination patterns, followed by Quantitative Microbial Risk Assessment (QMRA) to estimate infection probabilities. Tracer organisms seeded on high-touch surfaces spread to 50 % of sampled fomites within 4 h. A subsequent Targeted Hygiene intervention, using disinfecting wipes, sprays, or aerosols tailored to surface types, resulted in a statistically significant 97.36 % reduction in viral concentrations (1.57 log10 reduction, p < 0.0001). The proportion of cross-contaminated surfaces (i.e., non-seeded sites testing positive) decreased from 13 % to 2 %, and the overall percentage of positive surfaces dropped from 50 % to 42 %. QMRA modeling demonstrated that infection risks from a single fomite-hand-face contact were highest for rhinovirus, rotavirus, and adenovirus. Following intervention, infection risk was reduced by over 97 % for all modeled pathogens. Risk levels for all viruses and bacteria met the U.S. EPA and WHO benchmark of less than 1 infection per 10,000 exposures used in drinking water guidelines. Notably, bacterial infection risks, already low pre-intervention, were further reduced to meet the more stringent 1 infection per 1,000,000 risk threshold. This is the first study to integrate real-world human behavior, viral tracer data, and QMRA modeling to assess Targeted Hygiene in a hospitality setting. Findings support the implementation of evidence-based hygiene protocols that prioritize high-risk surfaces and timing, offering a sustainable approach to reducing infection risks in public environments.

Impedance-based method for the quantification of infectious SARS-CoV-2

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the etiologic agent involved in the coronavirus disease 2019 (COVID-19) pandemic. The development of infectious titration methods is crucial to provide data for a better understanding of transmission routes, as well as to validate the efficacy of inactivation treatments. Nevertheless, the low-throughput analytical capacity of traditional methods may be a limiting factor for a large screening of samples. The aim of the study was to develop a Real-Time Cell Analysis (RTCA) assay based on the measurement of cell impedance to quantify infectious SARS-CoV-2. The kinetics of cell impedance showed a virus-specific Cell Index (CI) drop. This enabled the correlation between viral concentrations and time at which a 50 % drop in CI values was observed (tCI50), with establishment of a standard curve. In parallel, the improved Spearman and Kärber method was used to quantify infectious titer since the virus-induced CI drop is correlated to the Cytopathic Effect. The estimated uncertainty was respectively 0.57, 0.36, and 0.26 log10 with 4, 8, and 16 wells per dilution. Thus, the RTCA assay is a powerful tool with a greatly simplified workflow for effective risk assessment in the field of food and environmental virology.

Shared sanitation facilities and risk of respiratory virus transmission in resource-poor settings: A COVID-19 modeling case study

Water supply and sanitation are essential household services frequently shared in resource-poor settings. Shared sanitation can increase the risk of enteric pathogen transmission due to suboptimal cleanliness of facilities used by large numbers of individuals. It also can potentially increase the risk of respiratory disease transmission. As sanitation is an essential need, shared sanitation facilities may act as important respiratory pathogen transmission venues even with strict control measures such as stay-at-home recommendations in place. This analysis explores how behavioral and infrastructural conditions surrounding shared sanitation may individually and interactively influence respiratory pathogen transmission. We developed an individual-based community transmission model using COVID-19 as a motivating example parameterized from empirical literature to explore how transmission in shared latrines interacts with transmission at the community level. We explored mitigation strategies, including infrastructural and behavioral interventions. Our review of empirical literature confirms that shared sanitation venues in resource-poor settings are relatively small with poor ventilation and high use patterns. In these contexts, shared sanitation facilities may act as strong drivers of respiratory disease transmission, especially in areas reliant on shared facilities. Decreasing dependence on shared latrines was most effective at attenuating sanitation-associated transmission. Improvements to latrine ventilation and handwashing behavior were also able to decrease transmission. The type and order of interventions are important in successfully attenuating disease risk, with infrastructural and engineering controls being most effective when administered first, followed by behavioral controls after successful attenuation of sufficient alternate transmission routes. Beyond COVID-19, our modeling framework can be extended to address water, sanitation, and hygiene measures targeted at a range of environmentally mediated infectious diseases.

Network-based virus dynamic simulation: Evaluating the fomite disinfection effectiveness on SARS-CoV-2 transmission in indoor environment

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is involved in aerosol particles and droplets excreted from a coronavirus disease 2019 (COVID-19) patient. Such aerosol particles or droplets including infectious virions can be attached on fomite, so fomite is not a negligible route for SARS-CoV-2 transmission within a community, especially in indoor environment. This necessarily evokes a need of fomite disinfection to remove virions, but the extent to which fomite disinfection breaks off virus transmission chain in indoor environment is still elusive. In this study, we evaluated the fomite disinfection effectiveness on COVID-19 case number using network analysis that reproduced the reported indoor outbreaks. In the established network, virus can move around not only human but also air and fomite while growing in human and decaying in air and on fomite, and infection success was determined based on the exposed virus amount and the equation of probability of infection. The simulation results have demonstrated that infectious virions on fomite should be kept less than a hundred to sufficiently reduce COVID-19 case, and every-hour disinfection was required to avoid stochastic increase in the infection case. This study gives us a practical disinfection manner for fomite to control SARS-CoV-2 transmission in indoor environment.

Harnessing Non-standard Nucleic Acids for Highly Sensitive Icosaplex (20-Plex) Detection of Microbial Threats for Environmental Surveillance

Environmental surveillance and clinical diagnostics heavily rely on the polymerase chain reaction (PCR) for target detection. A growing list of microbial threats warrants new PCR-based detection methods that are highly sensitive, specific, and multiplexable. Here, we introduce a PCR-based icosaplex (20-plex) assay for detecting 18 enteropathogen and two antimicrobial resistance genes. This multiplexed PCR assay leverages the self-avoiding molecular recognition system (SAMRS) to avoid primer dimer formation, the artificially expanded genetic information system (AEGIS) for amplification specificity, and next-generation sequencing for amplicon identification. Using parallelized multitarget TaqMan Array Cards (TAC) to benchmark performance of the 20-plex assay on wastewater, soil, and human stool samples, we found 90% agreement on positive calls and 89% agreement on negative calls. Additionally, we show how long-read and short-read sequencing information from the 20-plex can be used to further classify allelic variants of genes and distinguish subspecies. The strategy presented offers sensitive, affordable, and robust multiplex detection that can be used to support efforts in wastewater-based epidemiology, environmental monitoring, and human/animal diagnostics.

Antiviral Surface Coatings: From Pandemic Lessons to Visible-Light-Activated Films

The increasing need for effective antiviral strategies has led to the development of innovative surface coatings to combat the transmission of viruses via fomites. The aim of this review is to critically assess the efficacy of antiviral coatings in mitigating virus transmission, particularly those activated by visible light. The alarm created by the COVID-19 pandemic, including the initial uncertainty about the mechanisms of its spread, attracted attention to fomites as a possible source of virus transmission. However, later research has shown that surface-dependent infection mechanisms need to be carefully evaluated experimentally. By briefly analyzing virus-surface interactions and their implications, this review highlights the importance of shifting to innovative solutions. In particular, visible-light-activated antiviral coatings that use reactive oxygen species such as singlet oxygen to disrupt viral components have emerged as promising options. These coatings can allow for obtaining safe, continuous, and long-term active biocidal surfaces suitable for various applications, including healthcare environments and public spaces. This review indicates that while the significance of fomite transmission is context-dependent, advances in material science provide actionable pathways for designing multifunctional, visible-light-activated antiviral coatings. These innovations align with the lessons learned from the COVID-19 pandemic and pave the way for sustainable, broad-spectrum antiviral solutions capable of addressing future public health challenges.

A risk-risk tradeoff approach for incorporating the public's risk perceptions into quantitative microbial risk assessment

In public health, risk experts often define acceptable risk targets without community input. We developed a novel method for applying behavioral microeconomics to integrate individuals' risk preferences into risk assessment. To demonstrate this methodology, we explored a risk-risk tradeoff case scenario: increased asthma risk from increased cleaning and disinfection (C&D) and increased infection risk from decreased C&D for healthcare staff. Utilizing a risk-risk tradeoff (RRTO) framework, two datasets were informed with RRTO survey data describing the risks individuals would accept for one outcome to offset risk in another (i.e., "risk target"). A quantitative microbial risk assessment (QMRA) was deployed to output "critical concentrations," viral concentrations on surfaces that yield risk targets for a single contaminated surface touch and a work shift. Critical concentrations were over four orders of magnitude larger for single-touch scenarios. Critical concentrations across risk target datasets were similar. Using the RRTO framework to inform QMRA advances the incorporation of individuals' risk preferences in risk analyses outside economics.

Far-UVC (222 nm) irradiation effectively inactivates ssRNA, dsRNA, ssDNA, and dsDNA viruses as compared to germicidal UVC (254 nm)

Ultraviolet-C (UVC) irradiation is being used as an effective approach for the disinfection of pathogenic viruses present in air, surfaces, and water. Recently, far-UVC radiation (222 nm) emitted by KrCl* (krypton-chloride) excimer lamps have been recommended for disinfecting high-risk public spaces to reduce the presence and transmission of infectious viruses owing to limited human health exposure risks as compared to germicidal UVC (254 nm). In this study, the UVC inactivation performances of individual filtered KrCl* excimer lamp (222 nm) and germicidal UVC lamp (254 nm) were determined against four viruses, bacteriophages MS2, Phi6, M13, and T4, having different genome compositions (ssRNA, dsRNA, ssDNA and dsDNA, respectively) and shapes (i.e., spherical (Phi6), linear (M13), and icosahedral (MS2 and T4)). Here, the disinfection efficacies of filtered KrCl* excimer lamp (222 nm) and germicidal UVC lamp (254 nm) were evaluated for highly concentrated virus droplets that mimic the virus-laden droplets released from the infected person and deposited on surfaces as fomites. Filtered KrCl* excimer (222 nm) showed significantly better inactivation against all viruses having different genome compositions and structures compared to germicidal UVC (254 nm). The obtained sensitivity against the filtered KrCl* excimer (222 nm) was found to be in the order, T4 > M13 > Phi6 > MS2 whereas for the germicidal UVC (254 nm) it was T4 > M13 > MS2 > Phi6. These results provide a strong basis to promote the use of filtered KrCl* excimer lamps (222 nm) in disinfecting contagious viruses and to limit the associated disease spread in public places and other high-risk areas.

Resuspension and Dissemination of MS2 Virus from Flooring After Human Activities in Built Environment: Impact of Dust Particles

Resuspended particles from human activities can contribute to pathogen exposure via airborne fomite contamination in built environments. Studies investigating the dissemination of resuspended viruses are limited. The goal of this study was to explore viral dissemination after aerosolized resuspension via human activities on indoor flooring. Nylon carpet or wood flooring was seeded with virus (MS2) or virus laden dust then evaluated after activities, i.e., walking and vacuuming. Statistically significant differences were found in dispersal of virus laden dust after vacuuming carpet (p-value = 5.8 × 10-6) and wood (p-value = 0.003, distance > 12 in/30 cm). Significant differences were also found between floor materials and virus laden dust dispersal vacuuming (p = 2.09 × 10-5) and walking (p = 2.68 × 10-2). A quantitative microbial risk assessment (QMRA) scenario using Norovirus and a single fomite touch followed by a single hand-to-mouth touch indicated a statistically significant difference associated with virus laden dust particles and vacuuming carpet(p < 0.001). Infection risks were 1 to 5 log10 greater for dust exposure. The greatest risk reductions from fomites were seen across vacuuming carpet no-dust scenarios for surfaces <30 cm from flooring. More research is needed to determine the role resuspension plays in exposure and transmission of potentially infectious agents.

How long do bacteria, fungi, protozoa, and viruses retain their replication capacity on inanimate surfaces? A systematic review examining environmental resilience versus healthcare-associated infection risk by "fomite-borne risk assessment"

SUMMARYIn healthcare settings, contaminated surfaces play an important role in the transmission of nosocomial pathogens potentially resulting in healthcare-associated infections (HAI). Pathogens can be transmitted directly from frequent hand-touch surfaces close to patients or indirectly by staff and visitors. HAI risk depends on exposure, extent of contamination, infectious dose (ID), virulence, hygiene practices, and patient vulnerability. This review attempts to close a gap in previous reviews on persistence/tenacity by only including articles (n = 171) providing quantitative data on re-cultivable pathogens from fomites for a better translation into clinical settings. We have therefore introduced the new term "replication capacity" (RC). The RC is affected by the degree of contamination, surface material, temperature, relative humidity, protein load, organic soil, UV-light (sunlight) exposure, and pH value. In general, investigations into surface RC are mainly performed in vitro using reference strains with high inocula. In vitro data from studies on 14 Gram-positive, 26 Gram-negative bacteria, 18 fungi, 4 protozoa, and 37 viruses. It should be regarded as a worst-case scenario indicating the upper bounds of risks when using such data for clinical decision-making. Information on RC after surface contamination could be seen as an opportunity to choose the most appropriate infection prevention and control (IPC) strategies. To help with decision-making, pathogens characterized by an increased nosocomial risk for transmission from inanimate surfaces ("fomite-borne") are presented and discussed in this systematic review. Thus, the review offers a theoretical basis to support local risk assessments and IPC recommendations.

Review of animal transmission experiments of respiratory viruses: Implications for transmission risk of SARS-COV-2 in humans via different routes

Exploring transmission risk of different routes has major implications for epidemic control. However, disciplinary boundaries have impeded the dissemination of epidemic information, have caused public panic about "air transmission," "air-conditioning transmission," and "environment-to-human transmission," and have triggered "hygiene theater." Animal experiments provide experimental evidence for virus transmission, but more attention is paid to whether transmission is driven by droplets or aerosols and using the dichotomy to describe most transmission events. Here, according to characteristics of experiment setups, combined with patterns of human social interactions, we reviewed and grouped animal transmission experiments into four categories-close contact, short-range, fomite, and aerosol exposure experiments-and provided enlightenment, with experimental evidence, on the transmission risk of severe acute respiratory syndrome coronavirus (SARS-COV-2) in humans via different routes. When referring to "air transmission," context should be showed in elaboration results, rather than whether close contact, short or long range is uniformly described as "air transmission." Close contact and short range are the major routes. When face-to-face, unprotected, horizontally directional airflow does promote transmission, due to virus decay and dilution in air, the probability of "air conditioning transmission" is low; the risk of "environment-to-human transmission" highly relies on surface contamination and human behavior based on indirect path of "fomite-hand-mucosa or conjunctiva" and virus decay on surfaces. Thus, when discussing the transmission risk of SARS-CoV-2, we should comprehensively consider the biological basis of virus transmission, environmental conditions, and virus decay. Otherwise, risk of certain transmission routes, such as long-range and fomite transmission, will be overrated, causing public excessive panic, triggering ineffective actions, and wasting epidemic prevention resources.

Doff Thy Gown-Shedding Contact Precautions for COVID-19

SARS-CoV-2 is predominantly transmitted through aerosols (ie, airborne transmission); however, the US Centers for Disease Control and Prevention continue to recommend the use of contact precautions (a gown and gloves) for the care of patients with COVID-19. Infection-prevention guidelines should reflect the current science and eliminate this wasteful practice.

Harnessing non-standard nucleic acids for highly sensitive icosaplex (20-plex) detection of microbial threats

Environmental surveillance and clinical diagnostics heavily rely on the polymerase chain reaction (PCR) for target detection. A growing list of microbial threats warrants new PCR-based detection methods that are highly sensitive, specific, and multiplexable. Here, we introduce a PCR-based icosaplex (20-plex) assay for detecting 18 enteropathogen and two antimicrobial resistance genes. This multiplexed PCR assay leverages the self-avoiding molecular recognition system (SAMRS) to avoid primer dimer formation, the artificially expanded genetic information system (AEGIS) for amplification specificity, and next-generation sequencing for amplicon identification. We benchmarked this assay using a low-cost, portable sequencing platform (Oxford Nanopore) on wastewater, soil, and human stool samples. Using parallelized multi-target TaqMan Array Cards (TAC) to benchmark performance of the 20-plex assay, there was 74% agreement on positive calls and 97% agreement on negative calls. Additionally, we show how sequencing information from the 20-plex can be used to further classify allelic variants of genes and distinguish sub-species. The strategy presented offers sensitive, affordable, and robust multiplex detection that can be used to support efforts in wastewater-based epidemiology, environmental monitoring, and human/animal diagnostics.

Epidemiological modeling of SARS-CoV-2 in white-tailed deer (Odocoileus virginianus) reveals conditions for introduction and widespread transmission

Emerging infectious diseases with zoonotic potential often have complex socioecological dynamics and limited ecological data, requiring integration of epidemiological modeling with surveillance. Although our understanding of SARS-CoV-2 has advanced considerably since its detection in late 2019, the factors influencing its introduction and transmission in wildlife hosts, particularly white-tailed deer (Odocoileus virginianus), remain poorly understood. We use a Susceptible-Infected-Recovered-Susceptible epidemiological model to investigate the spillover risk and transmission dynamics of SARS-CoV-2 in wild and captive white-tailed deer populations across various simulated scenarios. We found that captive scenarios pose a higher risk of SARS-CoV-2 introduction from humans into deer herds and subsequent transmission among deer, compared to wild herds. However, even in wild herds, the transmission risk is often substantial enough to sustain infections. Furthermore, we demonstrate that the strength of introduction from humans influences outbreak characteristics only to a certain extent. Transmission among deer was frequently sufficient for widespread outbreaks in deer populations, regardless of the initial level of introduction. We also explore the potential for fence line interactions between captive and wild deer to elevate outbreak metrics in wild herds that have the lowest risk of introduction and sustained transmission. Our results indicate that SARS-CoV-2 could be introduced and maintained in deer herds across a range of circumstances based on testing a range of introduction and transmission risks in various captive and wild scenarios. Our approach and findings will aid One Health strategies that mitigate persistent SARS-CoV-2 outbreaks in white-tailed deer populations and potential spillback to humans.

Algorithm for community security risk assessment and influencing factors analysis by back propagation neural network

This paper aims to accurately assess and effectively manage various security risks in the community and overcome the challenges faced by traditional models in handling large amounts of features and high-dimensional data. Hence, this paper utilizes the back propagation neural network (BPNN) to optimize the security risk assessment model. A key challenge of researching community security risk assessment lies in accurately identifying and predicting a range of potential security threats. These threats may encompass natural disasters, public health crises, accidents, and social security issues. The intricate interplay of these risk factors, combined with the dynamic nature of community environments, presents difficulties for traditional risk assessment methodologies to address effectively. Initially, this paper delves into the factors influencing safety incidents within communities and establishes a comprehensive system of safety risk assessment indicators. Leveraging the adaptable and generalizable nature of the BPNN model, the paper proceeds to optimize the BPNN model, enhancing the security risk assessment model through this optimization. Subsequent comparison experiments with traditional models validate the rationality and effectiveness of the proposed model, with hidden layer nodes set at various levels like 10, 15, 20, 25, 30, and 35. These traditional models include Convolutional Neural Network (CNN), Long Short-Term Memory Network (LSTM), Bidirectional Encoder Representations from Transformers (BERT), Generative Pre-trained Transformer (GPT), and eXtreme Gradient Boosting (XGBOOST). Experimental findings demonstrate that with 20 hidden layer nodes, the optimized model achieves a remarkable final recognition accuracy of 99.1 %. Moreover, the optimized model exhibits significantly lower final function loss compared to models with different node numbers. Increasing the number of hidden layer nodes may diminish the optimized model's fit and accuracy. Comparison with traditional models reveals that the average accuracy of the optimized model in community risk identification reaches 98.5 %, with a maximum accuracy of 99.6 %. This marks an improvement of 9%-11 % in recognition accuracy across various risk factors compared to traditional models. Regarding system response time and resource utilization, the optimized model exhibits a response time ranging from 100 ms to 120 ms and consistently lower resource utilization rates across all scenarios, underscoring its efficiency in community security risk assessment. In conclusion, this experiment sheds light on the underlying mechanisms and patterns of community safety risk formation, offering novel perspectives and methodologies for researching community safety risk assessment. The paper concludes by presenting recommendations and strategies for addressing community safety risks based on experimental analysis.

COVID-19 transmission and control in land public transport: A literature review

Land public transport is an important link within and between cities, and how to control the transmission of COVID-19 in land public transport is a critical issue in our daily lives. However, there are still many inconsistent opinions and views about the spread of SARS-CoV-2 in land public transport, which limits our ability to implement effective interventions. The purpose of this review is to overview the literature on transmission characteristics and routes of the epidemic in land public transport, as well as to investigate factors affecting its spread and provide feasible measures to mitigate the infection risk of passengers. We obtained 898 papers by searching the Web of Science, Pubmed, and WHO global COVID database by keywords, and finally selected 45 papers that can address the purpose of this review. Land public transport is a high outbreak area for COVID-19 due to characteristics like crowding, inadequate ventilation, long exposure time, and environmental closure. Different from surface touch transmission and drop spray transmission, aerosol inhalation transmission can occur not only in short distances but also in long distances. Insufficient ventilation is the most important factor influencing long-distance aerosol transmission. Other transmission factors (e.g., interpersonal distance, relative orientation, and ambient conditions) should be noticed as well, which have been summarized in this paper. To address various influencing factors, it is essential to suggest practical and efficient preventive measures. Among these, increased ventilation, particularly the fresh air (i.e., natural ventilation), has proven to effectively reduce indoor infection risk. Many preventive measures are also effective, such as enlarging social distance, avoiding face-to-face orientation, setting up physical partitions, disinfection, avoiding talking, and so on. As research on the epidemic has intensified, people have broken down many perceived barriers, but more comprehensive studies on monitoring systems and prevention measures in land public transport are still needed.

Applications of Quantitative Microbial Risk Assessment to Respiratory Pathogens and Implications for Uptake in Policy: A State-of-the-Science Review

BACKGROUND

Respiratory tract infections are major contributors to the global disease burden. Quantitative microbial risk assessment (QMRA) holds potential as a rapidly deployable framework to understand respiratory pathogen transmission and inform policy on infection control.

OBJECTIVES

The goal of this paper was to evaluate, motivate, and inform further development of the use of QMRA as a rapid tool to understand the transmission of respiratory pathogens and improve the evidence base for infection control policies.

METHODS

We conducted a literature review to identify peer-reviewed studies of complete QMRA frameworks on aerosol inhalation or contact transmission of respiratory pathogens. From each of the identified studies, we extracted and summarized information on the applied exposure model approaches, dose-response models, and parameter values, including risk characterization. Finally, we reviewed linkages between model outcomes and policy.

RESULTS

We identified 93 studies conducted in 16 different countries with complete QMRA frameworks for diverse respiratory pathogens, including SARS-CoV-2, Legionella spp., Staphylococcus aureus, influenza, and Bacillus anthracis. Six distinct exposure models were identified across diverse and complex transmission pathways. In 57 studies, exposure model frameworks were informed by their ability to model the efficacy of potential interventions. Among interventions, masking, ventilation, social distancing, and other environmental source controls were commonly assessed. Pathogen concentration, aerosol concentration, and partitioning coefficient were influential exposure parameters as identified by sensitivity analysis. Most (84%, n = 78 ) studies presented policy-relevant content including a) determining disease burden to call for policy intervention, b) determining risk-based threshold values for regulations, c) informing intervention and control strategies, and d) making recommendations and suggestions for QMRA application in policy.

CONCLUSIONS

We identified needs to further the development of QMRA frameworks for respiratory pathogens that prioritize appropriate aerosol exposure modeling approaches, consider trade-offs between model validity and complexity, and incorporate research that strengthens confidence in QMRA results. https://doi.org/10.1289/EHP12695.

The airborne transmission of viruses causes tight transmission bottlenecks

The transmission bottleneck describes the number of viral particles that initiate an infection in a new host. Previous studies have used genome sequence data to suggest that transmission bottlenecks for influenza and SARS-CoV-2 involve few viral particles, but the general principles of virus transmission are not fully understood. Here we show that, across a broad range of circumstances, tight transmission bottlenecks are a simple consequence of the physical process of airborne viral transmission. We use mathematical modelling to describe the physical process of the emission and inhalation of infectious particles, deriving the result that that the great majority of transmission bottlenecks involve few viral particles. While exceptions to this rule exist, the circumstances needed to create these exceptions are likely very rare. We thus provide a physical explanation for previous inferences of bottleneck size, while predicting that tight transmission bottlenecks prevail more generally in respiratory virus transmission.

SARS-CoV-2 infection in brown-headed spider monkeys (Ateles fusciceps) at a wildlife rescue center on the coast of Ecuador-South America

Human populations can be affected in unpredictable ways by the emergence and spread of zoonotic diseases. The COVID-19 (coronavirus disease of 2019) pandemic was a reminder of how devastating these events can be if left unchecked. However, once they have spread globally, the impact of these diseases when entering non-exposed wildlife populations is unknown. The current study reports the infection of brown-headed spider monkeys (Ateles fusciceps) at a wildlife rescue center in Ecuador. Four monkeys were hospitalized, and all tested positive for SARS-CoV-2 (Severe acute respiratory syndrome coronavirus 2) by RT-qPCR (Quantitative Reverse Transcription PCR). Fecal samples (n = 12) from monkeys at the rescue center also tested positive; three zookeepers responsible for feeding and deworming the monkeys also tested positive, suggesting human-animal transmission. Whole genome sequencing identified most samples' omicron clade 22B BA.5 lineage. These findings highlight the threat posed by an emerging zoonotic disease in wildlife species and the importance of preventing spillover and spillback events during epidemic or pandemic events.IMPORTANCEAlthough COVID-19 (coronavirus disease of 2019) has been primarily contained in humans through widespread vaccination, the impact and incidence of SARS-CoV-2 (Severe acute respiratory syndrome coronavirus) and its transmission and epidemiology in wildlife may need to be addressed. In some natural environments, the proximity of animals to humans is difficult to control, creating perfect scenarios where susceptible wildlife can acquire the virus from humans. In these places, it is essential to understand how transmission can occur and to develop protocols to prevent infection. This study reports the infection of brown-headed spider monkeys with SARS-CoV-2, a red-listed monkey species, at a wildlife recovery center in Ecuador. This study reports the infection of brown-headed spider monkeys with SARS-CoV-2, indicating the potential for transmission between humans and wildlife primates and the importance of preventing such events in the future.

Decay pattern of SARS-CoV-2 RNA surface contamination in real residences

The COVID-19 pandemic has provided valuable lessons that deserve deep thought to prepare for the future. The decay pattern of surface contamination by SARS-CoV-2 RNA in the residences of COVID-19 patients is important but still unknown. We collected 2,233 surface samples from 21 categories of objects in 141 residences of COVID-19 patients in Shanghai when attacked by the omicron variant in spring 2022. Several characteristics of the patients and their residences were investigated to identify relevant associations. The decay of contamination was explored to determine the persistence. Approximately 8.7% of the surface samples were tested positive for SARS-CoV-2 RNA. The basin, water tap, and sewer inlet had the highest positive rates, all exceeding 20%. Only time was significantly associated with the level of surface contamination with SARS-CoV-2, showing a negative association. The decrease fit a first-order decay model with a decay rate of 0.77 ± 0.07 day-1, suggesting a 90% reduction in three days. Positive associations between the cumulative number of newly diagnosed patients in the same building and the positive rate of SARS-CoV-2 RNA in the public corridor were significant during the three days. Our results, in conjunction with the likely lower infectivity or viability, demonstrate that fomite transmission played a limited role in COVID-19 spread. The time determined SARS-CoV-2 RNA contamination, which was reduced by three days. This study is the first to show the decay patterns of SARS-CoV-2 contamination in real residential environments, providing insight into the patterns of transmission, as well as community-based prevention and control of similar threats.

Host and viral determinants of airborne transmission of SARS-CoV-2 in the Syrian hamster

It remains poorly understood how SARS-CoV-2 infection influences the physiological host factors important for aerosol transmission. We assessed breathing pattern, exhaled droplets, and infectious virus after infection with Alpha and Delta variants of concern (VOC) in the Syrian hamster. Both VOCs displayed a confined window of detectable airborne virus (24-48 hr), shorter than compared to oropharyngeal swabs. The loss of airborne shedding was linked to airway constriction resulting in a decrease of fine aerosols (1-10 µm) produced, which are suspected to be the major driver of airborne transmission. Male sex was associated with increased viral replication and virus shedding in the air. Next, we compared the transmission efficiency of both variants and found no significant differences. Transmission efficiency varied mostly among donors, 0-100% (including a superspreading event), and aerosol transmission over multiple chain links was representative of natural heterogeneity of exposure dose and downstream viral kinetics. Co-infection with VOCs only occurred when both viruses were shed by the same donor during an increased exposure timeframe (24-48 hr). This highlights that assessment of host and virus factors resulting in a differential exhaled particle profile is critical for understanding airborne transmission.

Perspectives on SARS-CoV-2 Cases in Zoological Institutions

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections in a zoological institution were initially reported in March 2020. Since then, at least 94 peer-reviewed cases have been reported in zoos worldwide. Among the affected animals, nonhuman primates, carnivores, and artiodactyls appear to be most susceptible to infection, with the Felidae family accounting for the largest number of reported cases. Clinical symptoms tend to be mild across taxa; although, certain species exhibit increased susceptibility to disease. A variety of diagnostic tools are available, allowing for initial diagnostics and for the monitoring of infectious risk. Whilst supportive therapy proves sufficient in most cases, monoclonal antibody therapy has emerged as a promising additional treatment option. Effective transmission of SARS-CoV-2 in some species raises concerns over potential spillover and the formation of reservoirs. The occurrence of SARS-CoV-2 in a variety of animal species may contribute to the emergence of variants of concern due to altered viral evolutionary constraints. Consequently, this review emphasizes the need for effective biosecurity measures and surveillance strategies to prevent and control SARS-CoV-2 infections in zoological institutions.

Evaluating infection risks and importance of hand hygiene during the household laundry process using a quantitative microbial risk assessment approach

BACKGROUND

Contaminated laundry contributes to infectious disease spread in residential and home health care settings. The objectives were to (1) evaluate pathogen transmission risks for individuals doing laundry, and (2) compare hand hygiene timing to reduce risks.

METHODS

A quantitative microbial risk assessment using experimental data from a laundry washing effectiveness study was applied to estimate infection risks from SARS-CoV-2, rotavirus, norovirus, nontyphoidal Salmonella, and Escherichia coli in 4 laundry scenarios: 1 baseline scenario (no hand hygiene event) and 3 hand hygiene scenarios (scenario 1: after moving dirty clothes to the washing machine, scenario 2: after moving washed clothes to the dryer, and scenario 3: hand hygiene events following scenario 1 and 2).

RESULTS

The average infection risks for the baseline scenario were all greater than 2 common risk thresholds (1.0×10-6and 1.0×10-4). For all organisms, scenario 1 yielded greater risk reductions (39.95%-99.86%) than scenario 2 (1.35%-55.25%). Scenario 3 further reduced risk, achieving 1.0×10-6(SARS-CoV-2) and 1.0×10-4risk thresholds (norovirus and E. coli).

CONCLUSIONS

The modeled results suggest individuals should reduce hand-to-facial orifice (eyes, nose, and mouth) contacts and conduct proper hand hygiene when handling contaminated garments. More empirical data are needed to confirm the estimated risks.

DATA AVAILABILITY STATEMENT

The data and code that support the findings of this study can be retrieved via a Creative Commons Zero v1.0 Universal license in GitHub at https://github.com/yhjung1231/Laundry-QMRAproject-2022.git DOI: http://doi.org/10.5281/zenodo.7122065.

Estimating spatially disaggregated probability of severe COVID-19 and the impact of handwashing interventions: The case of Zimbabwe

INTRODUCTION

The severity of COVID-19 disease varies substantially between individuals, with some infections being asymptomatic while others are fatal. Several risk factors have been identified that affect the progression of SARS-CoV-2 to severe COVID-19. They include age, smoking and presence of underlying comorbidities such as respiratory illness, HIV, anemia and obesity. Given that respiratory illness is one such comorbidity and is affected by hand hygiene, it is plausible that improving access to handwashing could lower the risk of severe COVID-19 among a population. In this paper, we estimate the potential impact of improved access to handwashing on the risk of respiratory illness and its knock-on impact on the risk of developing severe COVID-19 disease across Zimbabwe.

METHODS

Spatial generalized additive models were applied to cluster level data from the 2015 Demographic and Health Survey. These models were used to generate continuous (1km resolution) estimates of risk factors for severe COVID-19, including prevalence of major comorbidities (respiratory illness, HIV without viral load suppression, anemia and obesity) and prevalence of smoking, which were aggregated to district level alongside estimates of the proportion of the population under 50 from Worldpop data. The risk of severe COVID-19 was then calculated for each district using published estimates of the relationship between comorbidities, smoking and age (under 50) and severe COVID-19. Two scenarios were then simulated to see how changing access to handwashing facilities could have knock on implications for the prevalence of severe COVID-19 in the population.

RESULTS

This modeling conducted in this study shows that (1) current risk of severe disease is heterogeneous across the country, due to differences in individual characteristics and household conditions and (2) that if the quantifiable estimates on the importance of handwashing for transmission are sound, then improvements in handwashing access could lead to reductions in the risk of severe COVID-19 of up to 16% from the estimated current levels across all districts.

CONCLUSIONS

Taken alongside the likely impact on transmission of SARS-CoV-2 itself, as well as countless other pathogens, this result adds further support for the expansion of access to handwashing across the country. It also highlights the spatial differences in risk of severe COVID-19, and thus the opportunity for better planning to focus limited resources in high-risk areas in order to potentially reduce the number of severe cases.

An agent-based model to simulate SARS-CoV-2 contamination of surfaces and meat cuts in processing plants

At the beginning of the COVID-19 pandemic, several contamination clusters were reported in food-processing plants in France and several countries worldwide. Therefore, a need arose to better understand viral transmission in such occupational environments from multiple perspectives: the protection of workers in hotspots of viral circulation; the prevention of supply disruption due to the closure of plants; and the prevention of cluster expansion due to exports of food products contaminated by the virus to other locations. This paper outlines a simulation-based approach (using agent-based models) to study the effects of measures taken to prevent the contamination of workers, surfaces, and food products. The model includes user-defined parameters to integrate characteristics relating to SARS-CoV-2 (variant of concern to be considered, symptom onset…), food-processing plants (dimensions, ventilation…), and other sociodemographic transmission factors based on laboratory experiments as well as industrial and epidemiological investigations. Simulations were performed for a typical meat-processing plant in different scenarios for illustration purposes. The results suggested that increasing the mask-wearing ratio led to great reductions in the probability of observing clusters of more than 25 infections. In the case of clusters, masks being worn by all workers limited the presence of contamination (defined as levels of at least 5 log10 viral RNA copies) on meat cuts at less than 0.05 % and maintained the production capacity of the plant at optimal levels. Increasing the average distance between two workers from less than 1 m to more than 2 m decreased the cluster-occurrence probability by up to 15 % as well as contamination of food products during cluster situations. The developed approach can open up several perspectives in terms of potential communication-support tools for the agri-food sector and further reuses or adaptations for other hazards and occupational environments.

Host and viral determinants of airborne transmission of SARS-CoV-2 in the Syrian hamster

It remains poorly understood how SARS-CoV-2 infection influences the physiological host factors important for aerosol transmission. We assessed breathing pattern, exhaled droplets, and infectious virus after infection with Alpha and Delta variants of concern (VOC) in the Syrian hamster. Both VOCs displayed a confined window of detectable airborne virus (24-48 h), shorter than compared to oropharyngeal swabs. The loss of airborne shedding was linked to airway constriction resulting in a decrease of fine aerosols (1-10μm) produced, which are suspected to be the major driver of airborne transmission. Male sex was associated with increased viral replication and virus shedding in the air. Next, we compared the transmission efficiency of both variants and found no significant differences. Transmission efficiency varied mostly among donors, 0-100% (including a superspreading event), and aerosol transmission over multiple chain links was representative of natural heterogeneity of exposure dose and downstream viral kinetics. Co-infection with VOCs only occurred when both viruses were shed by the same donor during an increased exposure timeframe (24-48 h). This highlights that assessment of host and virus factors resulting in a differential exhaled particle profile is critical for understanding airborne transmission.

SARS-CoV-2 surface contamination in metro-Atlanta grocery stores

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.

COVID-19 cleaning protocol changes, experiences, and respiratory symptom prevalence among cleaning services personnel

Introduction

Cleaning protocols were changed in response to the COVID-19 pandemic with unknown occupational health impacts. There is evidence that COVID-19 transmission risks from contaminated surfaces are low and that exposure to cleaning products can increase risks of work-related asthma. The study objective was to investigate relationships between reported COVID-19-related changes in cleaning protocols and prevalence of asthma-related respiratory symptoms for asthmatic and non-asthmatic janitors and maids. A secondary objective was to characterize experiences of respiratory symptoms associated with cleaning and barriers to personal protective equipment (PPE) use.

Methods

Employees from two Tucson-based maid service companies (approximately 30 personnel in total) and one Phoenix-based school district (>300 janitors/custodians) were invited to participate in a written survey and/or a one-on-one interview in Spanish or English. Fisher's exact tests (α = 0.05) were used to test for statistically significant associations between reported respiratory symptoms by self-reported physician-diagnosed asthma status and changes in cleaning protocols. Interviews were transcribed and then analyzed by at least two researchers in English or Spanish.

Results

Eighty-three percent reported that cleaning protocols had changed during COVID-19, with the two most reported changes including increased cleaning frequency (92%) and change of application type (e.g., fog, spray, wipe) (53%). There was a statistically significant association between multiple respiratory symptoms and self-reported physician diagnosed asthma. Reporting a type of application change (e.g., fog, spray, wipe) and being awakened during the night by attack/episode of cough were statistically significantly associated (p = 0.04). Interviews elucidated respiratory issues related to fogging devices.

Discussion

This study provides preliminary evidence that changes in cleaning and disinfection protocols during COVID-19 (namely, the use of fogging/mechanical spraying devices) may have had negative impacts on the health of workers in the cleaning industry with little benefit to reducing COVID-19 risks. Further research is needed to evaluate the generalizability of our findings across larger geographical areas and to develop guidance for employers and employees on how to protect and promote respiratory health.

NS, Víšová I, Vrabcová M, Houska M, Anthi J, Spasovová M, Mustacová J, Štěrba J, Dostálek J, Tung CP, Yang AS, Jack R, Dejneka A, Hajdu J, Vaisocherová-Lísalová H. Negligible risk of surface transmission of SARS-CoV-2 in public transportation

BACKGROUND

Exposure to pathogens in public transport systems is a common means of spreading infection, mainly by inhaling aerosol or droplets from infected individuals. Such particles also contaminate surfaces, creating a potential surface-transmission pathway.

METHODS

A fast acoustic biosensor with an antifouling nano-coating was introduced to detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on exposed surfaces in the Prague Public Transport System. Samples were measured directly without pre-treatment. Results with the sensor gave excellent agreement with parallel quantitative reverse-transcription polymerase chain reaction (qRT-PCR) measurements on 482 surface samples taken from actively used trams, buses, metro trains and platforms between 7 and 9 April 2021, in the middle of the lineage Alpha SARS-CoV-2 epidemic wave when 1 in 240 people were COVID-19 positive in Prague.

RESULTS

Only ten of the 482 surface swabs produced positive results and none of them contained virus particles capable of replication, indicating that positive samples contained inactive virus particles and/or fragments. Measurements of the rate of decay of SARS-CoV-2 on frequently touched surface materials showed that the virus did not remain viable longer than 1-4 h. The rate of inactivation was the fastest on rubber handrails in metro escalators and the slowest on hard-plastic seats, window glasses and stainless-steel grab rails. As a result of this study, Prague Public Transport Systems revised their cleaning protocols and the lengths of parking times during the pandemic.

CONCLUSIONS

Our findings suggest that surface transmission played no or negligible role in spreading SARS-CoV-2 in Prague. The results also demonstrate the potential of the new biosensor to serve as a complementary screening tool in epidemic monitoring and prognosis.

Evaluating the impact of test-trace-isolate for COVID-19 management and alternative strategies

There are many contrasting results concerning the effectiveness of Test-Trace-Isolate (TTI) strategies in mitigating SARS-CoV-2 spread. To shed light on this debate, we developed a novel static-temporal multiplex network characterizing both the regular (static) and random (temporal) contact patterns of individuals and a SARS-CoV-2 transmission model calibrated with historical COVID-19 epidemiological data. We estimated that the TTI strategy alone could not control the disease spread: assuming R0 = 2.5, the infection attack rate would be reduced by 24.5%. Increased test capacity and improved contact trace efficiency only slightly improved the effectiveness of the TTI. We thus investigated the effectiveness of the TTI strategy when coupled with reactive social distancing policies. Limiting contacts on the temporal contact layer would be insufficient to control an epidemic and contacts on both layers would need to be limited simultaneously. For example, the infection attack rate would be reduced by 68.1% when the reactive distancing policy disconnects 30% and 50% of contacts on static and temporal layers, respectively. Our findings highlight that, to reduce the overall transmission, it is important to limit contacts regardless of their types in addition to identifying infected individuals through contact tracing, given the substantial proportion of asymptomatic and pre-symptomatic SARS-CoV-2 transmission.

Influence of experience, tenure, and organisational preparedness on nurses' readiness in responding to disasters: An exploration during the COVID-19 pandemic

Background

The coronavirus 2019 (COVID-19) pandemic has placed unprecedented challenges on the nursing practice, particularly in Poland. Nurses, as crucial healthcare service providers, have faced organisational disruptions, altered working conditions, and heightened professional anxieties.

Methods

We undertook a comprehensive survey across all medical centres in Lublin, Poland in 2020 to understand nurses' attitudes towards their roles and working conditions during the pandemic. This involved 470 nurses completing a questionnaire which focused on four pivotal areas: readiness to be on call in a disaster situation (even when not formally asked); willingness to work overtime in a disaster without additional compensation, preparedness to undertake health risks by caring for individuals with infectious diseases or exposure to hazardous substances, and willingness to be transferred to other departments during a disaster.

Results

We found that excessive workload, fear of infection, and feelings of helplessness significantly influenced nurses' readiness to work overtime, particularly when unpaid. We also presented the ethical dilemmas that nurses encountered during the pandemic and how these dilemmas affected their decision-making processes. We further explored the impact of variables such as nurses' professional experience, tenure, and level of organisational preparedness on their readiness to respond to crisis situations.

Conclusions

Gaining an understanding of nurses' perspectives is key for formulating strategies to bolster their professional engagements and resilience during crises. Addressing these issues can help build a more robust and well-prepared healthcare system that can effectively navigate future crises.

Combined Infection Control Interventions Protect Essential Food Workers from Occupational Exposures to SARS-CoV-2 in the Agricultural Environment

Essential food workers experience elevated risks of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection due to prolonged occupational exposures in food production and processing areas, shared transportation (car or bus), and employer-provided shared housing. Our goal was to quantify the daily cumulative risk of SARS-CoV-2 infection for healthy susceptible produce workers and to evaluate the relative reduction in risk attributable to food industry interventions and vaccination. We simulated daily SARS-CoV-2 exposures of indoor and outdoor produce workers through six linked quantitative microbial risk assessment (QMRA) model scenarios. For each scenario, the infectious viral dose emitted by a symptomatic worker was calculated across aerosol, droplet, and fomite-mediated transmission pathways. Standard industry interventions (2-m physical distancing, handwashing, surface disinfection, universal masking, ventilation) were simulated to assess relative risk reductions from baseline risk (no interventions, 1-m distance). Implementation of industry interventions reduced an indoor worker's relative infection risk by 98.0% (0.020; 95% uncertainty interval [UI], 0.005 to 0.104) from baseline risk (1.00; 95% UI, 0.995 to 1.00) and an outdoor worker's relative infection risk by 94.5% (0.027; 95% UI, 0.013 to 0.055) from baseline risk (0.487; 95% UI, 0.257 to 0.825). Integrating these interventions with two-dose mRNA vaccinations (86 to 99% efficacy), representing a worker's protective immunity to infection, reduced the relative infection risk from baseline for indoor workers by 99.9% (0.001; 95% UI, 0.0002 to 0.005) and outdoor workers by 99.6% (0.002; 95% UI, 0.0003 to 0.005). Consistent implementation of combined industry interventions, paired with vaccination, effectively mitigates the elevated risks from occupationally acquired SARS-CoV-2 infection faced by produce workers. IMPORTANCE This is the first study to estimate the daily risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection across a variety of indoor and outdoor environmental settings relevant to food workers (e.g., shared transportation [car or bus], enclosed produce processing facility and accompanying breakroom, outdoor produce harvesting field, shared housing facility) through a linked quantitative microbial risk assessment framework. Our model has demonstrated that the elevated daily SARS-CoV-2 infection risk experienced by indoor and outdoor produce workers can be reduced below 1% when vaccinations (optimal vaccine efficacy, 86 to 99%) are implemented with recommended infection control strategies (e.g., handwashing, surface disinfection, universal masking, physical distancing, and increased ventilation). Our novel findings provide scenario-specific infection risk estimates that can be utilized by food industry managers to target high-risk scenarios with effective infection mitigation strategies, which was informed through more realistic and context-driven modeling estimates of the infection risk faced by essential food workers daily. Bundled interventions, particularly if they include vaccination, yield significant reductions (>99%) in daily SARS-CoV-2 infection risk for essential food workers in enclosed and open-air environments.

RNA extraction-free workflow integrated with a single-tube CRISPR-Cas-based colorimetric assay for rapid SARS-CoV-2 detection in different environmental matrices

On-site environmental surveillance of viruses is increasingly important for infection prevention and pandemic control. Herein, we report a facile single-tube colorimetric assay for detecting severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) from environmental compartments. Using glycerol as the phase separation additive, reverse transcription recombinase polymerase amplification (RT-RPA), CRISPR-Cas system activation, G-quadruplex (G4) cleavage, and G4-based colorimetric reaction were performed in a single tube. To further simplify the test, viral RNA genomes used for the one-tube assay were obtained via acid/base treatment without further purification. The whole assay from sampling to visual readout was completed within 30 min at a constant temperature without the need for sophisticated instruments. Coupling the RT-RPA to CRISPR-Cas improved the reliability by avoiding false positive results. Non-labeled cost-effective G4-based colorimetric systems are highly sensitive to CRISPR-Cas cleavage events, and the proposed assay reached the limit of detection of 0.84 copies/µL. Moreover, environmental samples from contaminated surfaces and wastewater were analyzed using this facile colorimetric assay. Given its simplicity, sensitivity, specificity, and cost-effectiveness, our proposed colorimetric assay is highly promising for applications in on-site environmental surveillance of viruses.

Modeling the Interaction of Coronavirus Membrane Phospholipids with Photocatalitically Active Titanium Dioxide

The outbreak of viral infectious diseases urges airborne droplet and surface disinfection strategies, which may rely on photocatalytic semiconductors. A lipid bilayer membrane generally encloses coronaviruses and promotes the anchoring on the semiconductor surface, where, upon photon absorption, electron-hole pairs are produced, which can react with adsorbed oxygen-containing species and lead to the formation of reactive oxygen species (ROSs). The photogenerated ROSs may support the disruptive oxidation of the lipidic membrane and pathogen death. Density functional theory calculations are employed to investigate adsorption modes, energetics, and electronic structure of a reference phospholipid on anatase TiO2 nanoparticles. The phospholipid covalently bound on TiO2, engaging a stronger adsorption on the (101) than on the (001) surface. The energetically most stable structure involves the formation of four covalent bonds through phosphate and carbonyl oxygen atoms. The adsorbates show a reduction of the band gap compared with standalone TiO2, suggesting a significant interfacial coupling.

Modelling the impact of non-pharmaceutical interventions on workplace transmission of SARS-CoV-2 in the home-delivery sector

OBJECTIVE

We aimed to use mathematical models of SARS-COV-2 to assess the potential efficacy of non-pharmaceutical interventions on transmission in the parcel delivery and logistics sector.

METHODS

We devloped a network-based model of workplace contacts based on data and consultations from companies in the parcel delivery and logistics sectors. We used these in stochastic simulations of disease transmission to predict the probability of workplace outbreaks in this settings. Individuals in the model have different viral load trajectories based on SARS-CoV-2 in-host dynamics, which couple to their infectiousness and test positive probability over time, in order to determine the impact of testing and isolation measures.

RESULTS

The baseline model (without any interventions) showed different workplace infection rates for staff in different job roles. Based on our assumptions of contact patterns in the parcel delivery work setting we found that when a delivery driver was the index case, on average they infect only 0.14 other employees, while for warehouse and office workers this went up to 0.65 and 2.24 respectively. In the LIDD setting this was predicted to be 1.40, 0.98, and 1.34 respectively. Nonetheless, the vast majority of simulations resulted in 0 secondary cases among customers (even without contact-free delivery). Our results showed that a combination of social distancing, office staff working from home, and fixed driver pairings (all interventions carried out by the companies we consulted) reduce the risk of workplace outbreaks by 3-4 times.

CONCLUSION

This work suggests that, without interventions, significant transmission could have occured in these workplaces, but that these posed minimal risk to customers. We found that identifying and isolating regular close-contacts of infectious individuals (i.e. house-share, carpools, or delivery pairs) is an efficient measure for stopping workplace outbreaks. Regular testing can make these isolation measures even more effective but also increases the number of staff isolating at one time. It is therefore more efficient to use these isolation measures in addition to social distancing and contact reduction interventions, rather than instead of, as these reduce both transmission and the number of people needing to isolate at one time.

Human microbiome transfer in the built environment differs based on occupants, objects, and buildings

Compared to microbiomes on other skin sites, the bacterial microbiome of the human hand has been found to have greater variability across time. To increase understanding regarding the longitudinal transfer of the hand microbiome to objects in the built environment, and vice versa, 22 participants provided skin microbiome samples from their dominant hands, as well as from frequently and infrequently touched objects in their office environments. Additional longitudinal samples from home environments were obtained from a subset of 11 participants. We observed stability of the microbiomes of both the hand and built environments within the office and home settings; however, differences in the microbial communities were detected across the two built environments. Occupants' frequency of touching an object correlated to that object having a higher relative abundance of human microbes, yet the percent of shared microbes was variable by participants. Finally, objects that were horizontal surfaces in the built environment had higher microbial diversity as compared to objects and the occupants' hands. This study adds to the existing knowledge of microbiomes of the built environment, enables more detailed studies of indoor microbial transfer, and contributes to future models and building interventions to reduce negative outcomes and improve health and well-being.

Inactivation of SARS-CoV-2 and Other Enveloped and Non-Enveloped Viruses with Non-Thermal Plasma for Hospital Disinfection

As recently highlighted by the SARS-CoV-2 pandemic, viruses have become an increasing burden for health, global economy, and environment. The control of transmission by contact with contaminated materials represents a major challenge, particularly in hospital environments. However, the current disinfection methods in hospital settings suffer from numerous drawbacks. As a result, several medical supplies that cannot be properly disinfected are not reused, leading to severe shortages and increasing amounts of waste, thus prompting the search for alternative solutions. In this work, we report that non-thermal plasma (NTP) can effectively inactivate SARS-CoV-2 from non-porous and porous materials commonly found in healthcare facilities. We demonstrated that 5 min treatment with a dielectric barrier discharge NTP can inactivate 100% of SARS-CoV-2 (Wuhan and Omicron strains) from plastic material. Using porcine respiratory coronavirus (surrogate for SARS-CoV-2) and coxsackievirus B3 (highly resistant non-enveloped virus), we tested the NTP virucidal activity on hospital materials and obtained complete inactivation after 5 and 10 min, respectively. We hypothesize that the produced reactive species and local acidification contribute to the overall virucidal effect of NTP. Our results demonstrate the potential of dielectric barrier discharge NTPs for the rapid, efficient, and low-cost disinfection of healthcare materials.

Quantitative risk assessment of COVID-19 aerosol transmission indoors: a mechanistic stochastic web application

An increasing body of literature suggests that aerosol inhalation plays a primary role in COVID-19 transmission, particularly in indoor settings. Mechanistic stochastic models can help public health professionals, engineers, and space planners understand the risk of aerosol transmission of COVID-19 to mitigate it. We developed such model and a user-friendly web application to meet the need of accessible risk assessment tools during the COVID-19 pandemic. We built our model based on the Wells-Riley model of respiratory disease transmission, using quanta emission rates obtained from COVID-19 outbreak investigations. In this report, three modelled scenarios were evaluated and compared to epidemiological studies looking at similar settings: classrooms, weddings, and heavy exercise sessions. We found that the risk of long-range aerosol transmission increased 309-332% when people were not wearing masks, and 424-488% when the room was poorly ventilated in addition to no masks being worn across the scenarios. Also, the risk of transmission could be reduced by ∼40-60% with ventilation rates of 5 ACH for 1-4 h exposure events, and ∼70% with ventilation rates of 10 ACH for 4 h exposure events. Relative humidity reduced the risk of infection (inducing viral inactivation) by a maximum of ∼40% in a 4 h exposure event at 70% RH compared to a dryer indoor environment with 25% RH. Our web application has been used by more than 1000 people in 52 countries as of September 1st, 2021. Future work is needed to obtain SARS-CoV-2 dose-response functions for more accurate risk estimates.

Risk assessment of banknotes as a fomite of SARS-CoV-2 in cash payment transactions

The COVID 19 pandemic has triggered concerns and assumptions globally about transmission of the SARS-CoV-2 virus via cash transactions. This paper assesses the risk of contracting COVID-19 through exposure to SARS-CoV-2 via cash acting as a fomite in payment transactions. A quantitative microbial risk assessment was conducted for a scenario assuming an infectious person at the onset of symptoms, when virion concentrations in coughed droplets are at their highest. This person then contaminates a banknote by coughing on it and immediately hands it over to another person, who might then be infected by transferring the virions with a finger from the contaminated banknote to a facial mucous membrane. The scenario considered transfer efficiency of virions on the banknote to fingertips when droplets were still wet and after having dried up and subsequently being touched by finger printing or rubbing the object. Accounting for the likelihood of the scenario to occur by considering (1) a local prevalence of 100 COVID-19 cases/100,000 persons, (2) a maximum of about one-fifth of infected persons transmit high virus loads, and (3) the numbers of cash transactions/person/day, the risk of contracting COVID-19 via person-to-person cash transactions was estimated to be much lower than once per 39,000 days (107 years) for a single person. In the general populace, there will be a maximum of 2.6 expected cases/100,000 persons/day. The risk for a cashier at an average point of sale was estimated to be much less than once per 430 working days (21 months). The depicted scenario is a rare event, therefore, for a single person, the risk of contracting COVID-19 via person-to-person cash transactions is very low. At a point of sale, the risk to the cashier proportionally increases but it is still low.

Laboratory Evaluation of a Quaternary Ammonium Compound-Based Antimicrobial Coating Used in Public Transport during the COVID-19 Pandemic

The virucidal activity of the Zoono Z71 Microbe Shield surface sanitizer and protectant, a quaternary ammonium compound (QAC)-based antimicrobial coating that was used by the United Kingdom rail industry during the COVID-19 pandemic, was evaluated, using the bacteriophage ɸ6 as a surrogate for SARS-CoV-2. Immediately after application and in the absence of interfering substances, the product effectively reduced (>3 log10) the viability of ɸ6 on some materials that are typically used in rail carriages (stainless steel, high-pressure laminate, plastic). If, after the application of the product, these surfaces remained undisturbed, the antimicrobial coating retained its efficacy for at least 28 days. However, efficacy depended on the material being coated. The product provided inconsistent results when applied to glass surfaces and was ineffective (i.e., achieved <3 log10 reduction) when applied to a train arm rest that was made of Terluran 22. Regardless of the material that was coated or the time since application, the presence of organic debris (fetal bovine serum) significantly reduced the viricidal activity of the coating. Wiping the surface with a wetted cloth after the deposition of organic debris was not sufficient to restore efficacy. We conclude that the product is likely to be of limited effectiveness in a busy, multiuser environment, such as public transport. IMPORTANCE This study evaluated the performance of a commercially available antimicrobial coating that was used by the transport industry in the United Kingdom during the COVID-19 pandemic. While the product was effective against ɸ6, the efficacy of the coating depended upon the material to which it was applied. Similarly, and regardless of the surface material, the presence of organic debris severely impaired viricidal activity, and efficacy could not be recovered through wiping (cleaning) the surface. This highlights the importance of including relevant materials and conditions when evaluating antimicrobial coatings in the laboratory. Further efforts are required to identify suitable infection prevention and control practices for the transport industry.

Evaluation of steam heat as a decontamination approach for SARS-CoV-2 when applied to common transit-related materials

AIMS

The purpose of this study was to evaluate the efficacy of steam heat for inactivation of SARS-CoV-2 when applied to materials common in mass transit installations.

METHODS AND RESULTS

SARS CoV-2 (USA-WA1/2020) was resuspended in either cell culture media or synthetic saliva, inoculated (∼1 × 106 TCID50) onto porous and nonporous materials and subjected to steam inactivation efficacy tests as either wet or dried droplets. The inoculated test materials were exposed to steam heat ranging from 70°C to 90°C. The amount of infectious SARS-CoV-2 remaining after various exposure durations ranging from 1 to 60 s was assessed. Higher steam heat application resulted in higher inactivation rates at short contact times. Steam applied at 1-inch distance (∼90°C at the surface) resulted in complete inactivation for dry inoculum within 2 s of exposure (excluding two outliers of 19 test samples at the 5-s duration) and within 2-30 s of exposure for wet droplets. Increasing the distance to 2 inches (∼70°C) also increased the exposure time required to achieve complete inactivation to 15 or 30 s for materials inoculated with saliva or cell culture media, respectively.

CONCLUSIONS

Steam heat can provide high levels of decontamination (>3 log reduction) for transit-related materials contaminated with SARS-CoV-2 using a commercially available steam generator with a manageable exposure time of 2-5 s.

Cellular-level insight into biointerface: From surface charge modulation to boosted photocatalytic oxidative disinfection

Photocatalytic oxidative disinfection (POD) towards pathogenic bacteria has become a popular approach in public health due to its environmentally friendly antimicrobial capabilities. However, this approach is still limited by inherent fast electron-hole recombination within photocatalysts and poor interactions between bacterial cells and photogenerated reactive oxygen species (ROS) at the biointerface. Particularly, those ROS with extremely short migration distances cannot reach the bacterial cells before they deteriorate into less potent or neutral species, resulting in reduced antibacterial activities. By far, these phenomena are still poorly understood. Inspired by the fact that bacterial cells are negatively charged, we rationally designed a photocatalyst (i.e., g-C3N4/MIL-125-NH2) by coating a layer of positively charged quaternary ammonium compound (QAC) polymer onto the surface to enhance its affinity towards bacterial cells via electrostatic attractions. This surface-modulated photocatalyst is denoted as QAC@g-C3N4/MIL-125-NH2. The visualization and quantification of the electrostatic interactions between the bacterial cells and the QAC@g-C3N4/MIL-125-NH2 photocatalyst were conducted using a confocal laser scanning microscope and atomic force microscope, respectively. The results showed that the positively charged QAC layer did promote the bacteria-photocatalyst contact via electrostatic attractions. Due to the cooperative effects of bacterial cell adhesion and ROS generation, the POD performance of the photocatalyst is significantly enhanced. Notably, the photocatalyst achieves 3.20 logs of inactivation efficiency for Staphylococcus epidermidis within 60 min under visible light irradiation. This work provides insights into a mechanistic understanding of bacterial adhesion and disinfection at the biointerface and sheds light on rational photocatalyst design with surface charge modulation for antibacterial applications.

Transmission of SARS-CoV-2 in the workplace: Key findings from a rapid review of the literature

At the beginning of the COVID-19 pandemic, the primary route of transmission of the SARS-CoV-2 virus was not well understood. Research gathered from other respiratory infectious diseases, including other coronaviruses, was the basis for the initial perceptions for transmission of SARS-CoV-2. To better understand transmission of SARS-CoV-2, a rapid literature review was conducted from literature generated March 19, 2020, through September 23, 2021. 18,616 unique results were identified from literature databases and screened. Of these, 279 key articles were reviewed and abstracted covering critical topics such as environmental/workplace monitoring, sampling and analytical method evaluation, and the ability of the virus to remain intact and infectious during sampling. This paper describes the results of the rapid literature review, which evaluated pathways that contribute to transmission as well as the strengths and limitations of current sampling approaches. This review also evaluates how different factors, including environmental conditions and surface characteristics, could impact the transmission potential of SARS-CoV-2. A continual rapid review in the midst of a pandemic proved particularly useful for quickly understanding the transmission parameters of the virus and enabled us to comprehensively assess literature, respond to workplace questions, and evaluate our understanding as the science evolved. Air and surface sampling with the accompanying analytical methods were not generally effective in recovering SARS-CoV-2 viable virus or RNA in many likely contaminated environments. In light of these findings, the development of validated sampling and analysis methods is critical for determining worker exposure to SARS-CoV-2 and to assess the impact of mitigation efforts.

Commercial toilets emit energetic and rapidly spreading aerosol plumes

Aerosols can transmit infectious diseases including SARS-CoV-2, influenza and norovirus. Flushed toilets emit aerosols that spread pathogens contained in feces, but little is known about the spatiotemporal evolution of these plumes or the velocity fields that transport them. Using laser light to illuminate ejected aerosols we quantify the kinematics of plumes emanating from a commercial flushometer-type toilet, and use the motion of aerosol particles to compute velocity fields of the associated flow. The toilet flush produces a strong chaotic jet with velocities exceeding 2 m/s; this jet transports aerosols to heights reaching 1.5 m within 8 seconds of initiating a flush. Quantifying toilet plumes and associated flow velocities provides a foundation for future design strategies to mitigate plume formation or to disinfect pathogens within it.

A Novel Application of Risk-Risk Tradeoffs in Occupational Health: Nurses' Occupational Asthma and Infection Risk Perceptions Related to Cleaning and Disinfection during COVID-19

BACKGROUND

Nurses face the risk of new onset occupational asthma (OA) due to exposures to cleaning and disinfection (C&D) agents used to prevent infections in healthcare facilities. The objective of this study was to measure nurses' preferences when presented with simultaneous OA and respiratory viral infection (e.g., COVID-19) risks related to increased/decreased C&D activities.

METHODS

Nurses working in healthcare for ≥1 year and without physician-diagnosed asthma were recruited for an online anonymous survey, including four risk-risk tradeoff scenarios between OA and respiratory infection with subsequent recovery (Infect and Recovery) or subsequent death (Infect and Death). Nurses were presented with baseline risks at hypothetical "Hospital 1", and were asked to choose Hospital 2 (increased OA risk to maintain infection risk), Hospital 3 (increased infection risk to maintain OA risk), or indicate that they were equally happy.

RESULTS

Over 70% of nurses were willing to increase infection risk to maintain baseline OA risk if they were confident they would recover from the infection. However, even when the risk of infection leading to death was much lower than OA, most nurses were not willing to accept a larger (but still small) risk of death to avoid doubling their OA risk. Age, work experience, and ever having contracted or knowing anyone who has contracted a respiratory viral infection at work influenced choices.

CONCLUSIONS

We demonstrate the novel application of a risk-risk tradeoff framework to address an occupational health issue. However, more data are needed to test the generalizability of the risk preferences found in this specific risk-risk tradeoff context.

Physical education student teachers' wellbeing during Covid-19: Resilience resources and challenges from school placement

The coronavirus 2019 (Covid-19) pandemic has given rise to significant global challenges across education, and specifically in the physical education teacher education (PETE) community. Students attending teacher education programmes during the Covid-19 pandemic have experienced an abrupt and unprecedented pedagogical transition from a face-to-face capacity to remote teaching, learning, and assessment environments. Crucially, student teachers' school placement experiences faced increased challenges and practical implications from additional environmental and social changes. In the context of continued global and national challenges for initial teacher education (ITE) programmes, the present qualitative study, using a representative sample of 24 student physical education (PE) teachers from a PETE programme, investigates the perceived implications of the Covid-19 pandemic on student teachers' practice and wellbeing during their final 2020/2021 academic year. Results indicate that student teachers maintain that exercise, connections with the university and school placement communities, alongside personal and professional organisation skills serve as resilience resources protecting their wellbeing. Conversely, student teachers express that school placement isolation, restricted PE delivery, increased workload, low teacher efficacy, and the responsibility to implement Covid-19 behaviour regulations presented as challenges that negatively affect their wellbeing. The paper concludes with practices that may further support PETE and ITE programmes and their student teachers to maintain a stable level of wellbeing throughout their careers.

Genetic Load of SARS-CoV-2 in Aerosols Collected in Operating Theaters

After the outbreak of COVID-19, additional protocols have been established to prevent the transmission of the SARS-CoV-2 from the patient to the health personnel and vice versa in health care settings. However, in the case of emergency surgeries, it is not always possible to ensure that the patient is not infected with SARS-CoV-2, assuming a potential source of transmission of the virus to health personnel. This work aimed to evaluate the presence of the SARS-CoV-2 and quantify the viral load in indoor air samples collected inside operating rooms, where emergency and scheduled operations take place. Samples were collected for 3 weeks inside two operating rooms for 24 h at 38 L/min in quartz filters. RNA was extracted from the filters and analyzed using RT-qPCR targeting SARS-CoV-2 genes E, N1 and N2 regions. SARS-CoV-2 RNA was detected in 11.3% of aerosol samples collected in operating rooms, despite with low concentrations (not detected at 13.5 cg/m3 and 10.5 cg/m3 in the scheduled and emergency operating rooms, respectively). Potential sources of airborne SARS-CoV-2 could be aerosolization of the virus during aerosol-generating procedures and in open surgery from patients that might have been recently infected with the virus, despite presenting a negative COVID-19 test. Another source could be related to health care workers unknowingly infected with the virus and exhaling SARS-CoV-2 virions into the air. These results highlight the importance of reinforcing preventive measures against COVID-19 in operating rooms, such as the correct use of protective equipment, screening programs for health care workers, and information campaigns. IMPORTANCE Operating rooms are critical environments in which asepsis must be ensured. The COVID-19 pandemic entailed the implementation of additional preventative measures in health care settings, including operating theaters. Although one of the measures is to operate only COVID-19 free patients, this measure cannot be always implemented, especially in emergency interventions. Therefore, a surveillance campaign was conducted during 3 weeks in two operating rooms to assess the level of SARS-CoV-2 genetic material detected in operating theaters with the aim to assess the risk of COVID-19 transmission during operating procedures. SARS-CoV-2 genetic material was detected in 11% of aerosol samples collected in operating rooms, despite with low concentrations. Plausible SARS-CoV-2 sources have been discussed, including patients and health care personnel infected with the virus. These results highlight the importance of reinforcing preventive measures against COVID-19 in operating rooms, such as the correct use of protective equipment, screening programs for health care workers and information campaigns.

Prerequisite for COVID-19 Prediction: A Review on Factors Affecting the Infection Rate

Since the year 2020, coronavirus disease 2019 (COVID-19) has emerged as the dominant topic of discussion in the public and research domains. Intensive research has been carried out on several aspects of COVID-19, including vaccines, its transmission mechanism, detection of COVID-19 infection, and its infection rate and factors. The awareness of the public related to the COVID-19 infection factors enables the public to adhere to the standard operating procedures, while a full elucidation on the correlation of different factors to the infection rate facilitates effective measures to minimize the risk of COVID-19 infection by policy makers and enforcers. Hence, this paper aims to provide a comprehensive and analytical review of different factors affecting the COVID-19 infection rate. Furthermore, this review analyses factors which directly and indirectly affect the COVID-19 infection risk, such as physical distance, ventilation, face masks, meteorological factor, socioeconomic factor, vaccination, host factor, SARS-CoV-2 variants, and the availability of COVID-19 testing. Critical analysis was performed for the different factors by providing quantitative and qualitative studies. Lastly, the challenges of correlating each infection risk factor to the predicted risk of COVID-19 infection are discussed, and recommendations for further research works and interventions are outlined.