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Bacillus subtilis subsp. niger spore and Staphylococcus albus are typical biological indicators for the inactivation of airborne pathogens. The present study characterized and compared the behaviors of B. subtilis subsp. niger spores and S. albus in regard to inactivation by chlorine dioxide (ClO2) gas under different gas concentrations and relative humidity (RH) conditions. The inactivation kinetics under different ClO2 gas concentrations (1 to 5 mg/liter) were determined by first-order and Weibull models. A new model (the Weibull-H model) was established to reveal the inactivation tendency and kinetics for ClO2 gas under different RH conditions (30 to 90%). The results showed that both the gas concentration and RH were significantly (P<0.05) and positively correlated with the inactivation of the two chosen indicators. There was a rapid improvement in the inactivation efficiency under high RH (>70%). Compared with the first-order model, the Weibull and Weibull-H models demonstrated a better fit for the experimental data, indicating nonlinear inactivation behaviors of the vegetative bacteria and spores following exposure to ClO2 gas. The times to achieve a six-log reduction of B. subtilis subsp. niger spore and S. albus were calculated based on the established models. Clarifying the kinetics of inactivation of B. subtilis subsp. niger spores and S. albus by ClO2 gas will allow the development of ClO2 gas treatments that provide an effective disinfection method. [ABSTRACT FROM AUTHOR]

IN 2003, a health crisis took place that severely tested Hong Kong, among a number of other parts of the world, with at 15 June a death toll in the city of 295 (out of 1,755 cases). Schools were closed, an apartment block was quarantined, and businesses suffered as people stayed home. Because no one at that time knew much about what came to be called ‘severe acute respiratory syndrome’ (shortened to both SARS and Sars), the disease offered a ‘blank screen’ onto which various fears could be projected. It seemed to spread directly to close contacts – but airborne contagion could not be ruled out. The death rate was under five percent, but there was a possibility that it could become more virulent. It might turn out like any other flu-like illness, or like the 1918 flu pandemic that killed millions. In addition, it was the perfect mechanism for Hong Kong to project its current uncertainties over its image and place in the world. Thus, the ‘pragmatic handling’ of this event in the major English language newspaper of the city, the South China Morning Post, holds much linguistic interest. The SCMP is a major English-language newspaper in East Asia. [ABSTRACT FROM AUTHOR]

Background: As the global community begins recovering from the COVID-19 pandemic, the challenges due to its aftermath remain. This health crisis has highlighted challenges associated with airborne pathogens and their capacity for rapid transmission. While many solutions have emerged to tackle this challenge, very few devices exist that are inexpensive, easy to manufacture, and versatile enough for various settings. Methods: This paper presents a novel suction device designed to counteract the spread of aerosols and droplets and be cost-effective and adaptable to diverse environments. We also conducted an experimental study to evaluate the device's effectiveness using an artificial cough generator, a particle counter, and a mannequin in an isolated system. We measured droplet removal rates with simulated single and repeated cough incidents. Also, measurements were taken at four distinct areas to compare its effectiveness on direct plume versus indirect particle removal. Results: The device reduced airborne disease transmission risk, as evidenced by its capacity to decrease the half-life of aerosol volume from 23.6 minutes to 15.6 minutes, effectively capturing aerosol-sized droplets known for their extended airborne persistence. The suction device lessened the peak total droplet volume from peak counts. At 22 minutes post peak droplet count, the count had dropped 24% without the suction device and 43% with the suction device. Conclusions: The experiment's findings confirm the suction device's capability to effectively remove droplets from the environment, making it a vital tool in enhancing indoor air quality. Given the sustained performance of the suction device irrespective of single or multiple cough events, this demonstrates its potential utility in reducing the risk of airborne disease transmission. 3D printing for fabrication opens the possibility of a rapid iterative design process, flexibility for different configurations, and rapid global deployment for future pandemics. [ABSTRACT FROM AUTHOR]

In comparison with other respiratory viruses, the current COVID-19 pandemic's rapid seizing the world can be attributed to indirect (contact) way of transmission of SARS-CoV-2 virus in addition to the regular airborne way. A significant part of indirect transmission is made through cash bank notes. SARS-CoV-2 remains on cash paper money for period around four times larger than influenza A virus and is absorbed by cash notes two and a half times more effectively than influenza A (our model). During the pandemic, cryptocurrencies have gained attractiveness as an "epidemiologically safe" means of transactions. On the basis of the authors' gallop polls performed online with social networks users in 44 countries in 2020–2021 (the total number of clear responses after the set repair 32,115), around 14.7% of surveyed participants engaged in cryptocurrency-based transactions during the pandemic. This may be one of the reasons of significant rise of cryptocurrencies rates since mid-March 2020 till the end of 2021. The paper discusses the reasons for cryptocurrency attractiveness during the COVID-19 pandemic. Among them, there are fear of SARS-CoV-2 spread via cash contacts and the ability of the general population to mine cryptocurrencies. The article also provides a breakdown of the polled audience profile to determine the nationalities that have maximal level of trust to saving and transacting money as cryptocurrencies. [ABSTRACT FROM AUTHOR]

In the wake of the COVID-19 pandemic, prioritizing indoor air quality has emerged as a crucial measure for preventing infections. Effective ventilation is vital in mitigating airborne pathogen transmission and maintaining a healthy indoor environment by diluting and removing infectious particles from enclosed spaces. However, increasing the supply of pathogen-free air to enhance infection control can lead to a rise in energy consumption. Nevertheless, evaluating the overall efficacy of ventilation-based infection prevention strategies while considering their energy requirements has posed challenges. This scientific paper introduces the ICEE (Infection Control's Energy Efficiency) index, a newly developed simple integrated index to assess the effectiveness of ventilation strategies in reducing infection risks while accounting for associated energy demands. The paper reviews the current understanding of ventilation strategies, their impact on infection prevention, and their corresponding energy consumption. By employing a straightforward analytical approach, this metric offers a comprehensive framework to optimize ventilation systems for both infection prevention and energy efficiency. To quantify infection risk, a simplified equation model is utilized, incorporating factors such as ventilation effectiveness and filter efficiency, in case of recirculation. Energy demand is determined using approximations and relevant values from existing literature. Reference cases are defined, distinguishing between natural and mechanically ventilated scenarios, as these reference situations influence the energy-related effects of any implemented measures. The paper outlines the methodology employed to develop the index and illustrates its applicability through exemplary measures. The proposed index yields valuable insights for the design, operation, and retrofitting of ventilation systems, enabling informed decision-making towards fostering a healthier and more sustainable built environment. [ABSTRACT FROM AUTHOR]

Air conditioning systems can play a positive or negative role in the spread of COVID-19 infection. The importance of sufficient outdoor air changes in buildings was highlighted by the World Health Organization, therefore these should be guaranteed by mechanical ventilation systems or adequate air conditioning systems. The proposed case study concerns the optimal number of outdoor air changes to limit COVID-19 contagion for a school building in Central Italy. The Wells–Riley model is used to assess the risk of airborne infection, while energy consumption is calculated by a dynamic energy simulation software. The scope of the paper offers an innovative method to define the optimal ventilation strategy for the building's HVAC system design to reduce the risk of infection with limited increases in energy consumption and greenhouse gas emissions. Results show that the desirable approach is the one in which the same low value of contagion risk is set in all rooms. This new approach results in significant energy savings, compared to the most common ones (setting the same high outdoor air rates for all rooms) to counteract the risk of infection. Finally, the zero-emission building target is verified by introducing a suitable photovoltaic system to offset pollutant emissions. [ABSTRACT FROM AUTHOR]

Background: Mycobacterium tuberculosis, a bacterium that relies on its human host to achieve airborne transmission and existence, is the primary cause of tuberculosis (TB), a disease that is vital to public health. Aim: To update the society on tuberculosis diagnostic and treatment delays among patients in Uganda. Materials and Methods: The review paper utilized different search engines, such as Pubmed Central, Scopus, Web of Science, Google Scholar, and so forth, to conduct this review paper. Results: Delays in diagnosis could cause diseases to spread throughout the community, progress more quickly, and increase mortality. With many populations experiencing TB diagnostic delay and less than a third of the population experiencing TB treatment delay, the rates of tuberculosis diagnosis and treatment delays are high. Conclusion: The delay in diagnosing and treating tuberculosis in men is positively correlated with knowledge of the disease's symptoms and the regular use of a handkerchief or both hands to cover the mouth and nose while coughing or sneezing. [ABSTRACT FROM AUTHOR]

Tolerance graphs were introduced in 1982 by M. C. Golumbic and C. L. Monma as a generalization of interval graphs. In this paper, we introduce tolerance fuzzy graphs as a generalization of tolerance graphs, and apply them to a modeling of a transmission of airborne diseases. [ABSTRACT FROM AUTHOR]

The paper presents a framework for probabilistic assessment of likelihood of infection from airborne diseases in confined spaces which are continuously occupied for relatively long periods (e.g., school classrooms). The proposed approach is based on a combination of computational fluid dynamics (CFD) pre-calculations and analytical post-processing, to define relevant indices of infection probability. The practical applicability of the method is demonstrated through a case study, where different ventilation scenarios are considered for a school classroom. Corresponding infection probability indices are determined globally for the group of occupants. Furthermore, since the method does not rely on the well-mixing assumption, local probability indices are determined for each occupied location. The obtained results confirm the intuition that an increase of ventilation and/or air filtration reduces the overall likelihood of infection, though the observed positive effect is not uniform within the space. The presented methodology can also be considered as complementary to simpler approaches. [ABSTRACT FROM AUTHOR]

Dental aerosol-generating procedures produce a large amount of splatters and aerosols that create a major concern for airborne disease transmission, such as COVID-19. This study established a method to visualise splatter and aerosol contamination by common dental instrumentation, namely ultrasonic scaling, air-water spray, high-speed and low-speed handpieces. Mock dental procedures were performed on a mannequin model, containing teeth in a typodont and a phantom head, using irrigation water containing fluorescein dye as a tracer. Filter papers were placed in 10 different locations to collect splatters and aerosols, at distances ranging from 20 to 120 cm from the source. All four types of dental equipment produced contamination from splatters and aerosols. At 120 cm away from the source, the high-speed handpiece generated the greatest amount and size (656 ± 551 μm) of splatter particles, while the triplex syringe generated the largest amount of aerosols (particle size: 1.73 ± 2.23 μm). Of note, the low-speed handpiece produced the least amount and size (260 ± 142 μm) of splatter particles and the least amount of aerosols (particle size: 4.47 ± 5.92 μm) at 120 cm. All four dental AGPs produce contamination from droplets and aerosols, with different patterns of distribution. This simple model provides a method to test various preventive strategies to reduce risks from splatter and aerosols. [ABSTRACT FROM AUTHOR]

We investigated a norovirus outbreak (genotype GII.2) affecting 9 members of a soccer team. Illness was associated with touching a reusable grocery bag or consuming its packaged food contents (risk difference, 0.636; P < .01). By polymerase chain reaction, GII norovirus was recovered from the bag, which had been stored in a bathroom used before the outbreak by a person with norovirus-like illness. Airborne contamination of fomites can lead to subsequent point-source outbreaks. When feasible, we recommend dedicated bathrooms for sick persons and informing cleaning staff (professional or otherwise) about the need for adequate environmental sanitation of surfaces and fomites to prevent spread. [ABSTRACT FROM AUTHOR]

The effectiveness of face masks for preventing airborne transmission has been debated heavily during the COVID-19 pandemic. This paper investigates the filtration efficiency for four different face mask materials, two professional and two homemade, for different airflow conditions using model experiments and artificially generated water droplets. The size range chosen represents particles with the largest volume that can be suspended in air. The particles are detected using double pulsed interferometric particle imaging, from which it is possible to estimate the positions, velocity, and size of individual particles. It is found that all the tested face masks are efficient in preventing particles from transmission through the mask material. In the presence of leakage, particles larger than approximately 100 μ m are completely removed from the air stream. The filtration efficiency decreases with the decreasing particle size to approximately 80 % for 15 μ m particles. The size dependency in the leakage is mainly due to the momentum of the larger particles. The results show that even simple face mask materials with leakage prevent a large portion of the emitted particles in the 15–150 μ m range. [ABSTRACT FROM AUTHOR]

Presents several abstracts on dermatology published in the July 1998 issue of the 'British Journal of Dermatology.' 'Cinnamate Sensitivity–Case Report,' by Sandra Campbell; 'Frullania Dermatitis in Cornish Foresters,' by P.W. Bowers and C.G. Julian; 'Airborne Contact Dermatitis Caused by Microscopy Immersion Fluid Containing Epoxy Resin,' by S. Sommer, C.L. Wilson and S.M. Wilkinson.

Thiourea and its derivatives have been widely used in industry since the beginning of this century, but it was only in the late 1960s that reports of cases of contact dermatitis to these compounds began to appear in the literature. This literature is reviewed. We have observed eight cases of diphenylthiourea sensitivity in patients sensitive to adhesive tape. Four cases are presented of sensitivity to thiourea compounds in diazo-sensitized paper. Three of these patients were contact allergic to dimethylthiourea, and the other was contact and photocontact allergic to thiourea. These skin problems were mainly induced by airborne contact. [ABSTRACT FROM AUTHOR]

Recently, the COVID-19 virus pandemic has led to many studies on the airborne transmission of expiratory droplets. While limited experiments and on-site measurements offer qualitative indication of potential virus spread rates and the level of transmission risk, the quantitative understanding and mechanistic insights also indispensably come from careful theoretical modeling and numerical simulation efforts around which a surge of research papers has emerged. However, due to the highly interdisciplinary nature of the topic, numerical simulations of the airborne spread of expiratory droplets face serious challenges. It is essential to examine the assumptions and simplifications made in the existing modeling and simulations, which will be reviewed carefully here to better advance the fidelity of numerical results when compared to the reality. So far, existing review papers have focused on discussing the simulation results without questioning or comparing the model assumptions. This review paper focuses instead on the details of the model simplifications used in the numerical methods and how to properly incorporate important processes associated with respiratory droplet transmission. Specifically, the critical issues reviewed here include modeling of the respiratory droplet evaporation, droplet size distribution, and time-dependent velocity profile of air exhaled from coughing and sneezing. According to the literature review, another problem in numerical simulations is that the virus decay rate and suspended viable viral dose are often not incorporated; therefore here, empirical relationships for the bioactivity of coronavirus are presented. It is hoped that this paper can assist researchers to significantly improve their model fidelity when simulating respiratory droplet transmission. [ABSTRACT FROM AUTHOR]

Since the onset of the pandemic, the cruise industry has faced substantial challenges, experiencing an 81% year-on-year decline in 2020. Notably, China's cruise industry has remained shuttered for nearly two years. The conventional epidemiological investigations relying on human memory have proven inadequate in regard to swiftly and reliably identifying high-risk populations, thus leading to excessive pandemic prevention or other inappropriate measures. Furthermore, current research endeavors have not adequately addressed the critical issues of isolation location selection and the estimation of isolation scale within multi-zone indoor environments. Therefore, how to control the epidemic with minimal impact on the public has become an urgent problem. To solve the problems mentioned above, a multi-zone infection risk assessment model of airborne virus transmission was proposed to rapidly qualify the risk of infection, identify the high-risk population, and provide guidance. The model can be divided into two parts, including a multi-zone airflow model and a risk assessment model based on the Wells–Riley model. A large in-service ro-ro passenger ship already in service was used for the application of the proposed method. The results show that the number of isolated rooms shall be at least 5% of the occupancy and the isolation location can be chosen through the multi-zone infection risk assessment model. This paper provides insights into risk assessment to mitigate the spread of epidemics on a large cruise ship, and the method can be easily applied to all kinds of multi-zone indoor environments. [ABSTRACT FROM AUTHOR]

Background: The research shows a growing trend in using an electronic platform to supplement or replace traditional paper-based informed consent processes. Instead of the traditionally written informed consent document, electronic informed consent (eConsent) may be used to assess the research subject's comprehension of the information presented. By doing so, respect for persons as one of the research ethical principles can be upheld. Furthermore, these electronic methods may reduce potential airborne infection exposures, particularly during the pandemic, thereby adhering to the beneficence and nonmaleficence principle. This scoping review aims to identify the ethics related criteria that have been included in electronic informed consent processes and to synthesize and map these criteria to research ethics principles, in order to identify the gaps, if any, in current electronic informed consent processes.Methods: The search was performed based on internet search and three main databases: PubMed, SCOPUS and EBSCO. PRISMA Extension for Scoping Reviews (PRISMA-ScR): Checklist and Explanation guideline was used to report this work.Results: Of 34 studies that met the inclusion criteria, 242 essential original constructs were collated, and 7 concepts were derived. Digital content showed the highest percentage of collated original constructs (27%, n = 65) followed by accessibility (24%, n = 56), comprehension engagement (18%, n = 43), autonomy (14%, n = 34), confidentiality (11%, n = 25), language (5%, n = 13), and parental consent (1%, n = 2). Twenty-five new items were synthesized for eConsent criteria which may provide guidance for ethical review of research involving eConsent.Conclusion: The current study adds significant value to the corpus of knowledge in research ethics by providing ethical criteria on electronic informed consent based on evidence-based data. The new synthesized items in the criteria can be readily used as an initial guide by the IRB/REC members during a review process on electronic informed consent and useful to the future preparation of a checklist. [ABSTRACT FROM AUTHOR]

Tuberculosis (TB) is a communicable, airborne infection caused by the bacillus Mycobacterium tuberculosis. Pulmonary tuberculosis (PTB) is the most common presentation, although infection can spread anywhere to cause extra-pulmonary tuberculosis (EPTB). In this paper, a novel fractional order mathematical model is designed for the transmission dynamics of tuberculosis. Uninfected vulnerable individuals are categorized into the following: susceptible with underline ailment and susceptible without underline ailment. The research seeks to qualitatively and quantitatively analyze the proposed model and suggests comprehensive intervention measures for the control of tuberculosis among individuals with underline ailment. Some of the major highlights from the numerical investigation points out that TB vaccination is key to reducing the spread of TB among individuals with underline ailment. Furthermore, efforts to step down the spread of TB through awareness campaigns could significantly reduce the burden of the disease among individuals with co-morbidity. [ABSTRACT FROM AUTHOR]

In healthcare settings, controlling airborne contaminants is crucial for ensuring the safety of healthcare workers and patients, especially in isolation rooms designed with negative pressure systems. This paper, a novel experimental study of the distribution of airborne contamination within an Airborne Infection Isolation Room (AIIR) using tracer gas, identifies patients in Iraq to reduce the pollution and infection disease from a patient with COVID-19 or any other Respiratory patient disease by using a negative pressure room Terms of condition at three different Air Change (ACH) 6, 9 and 12 ACH. Concentrations of airborne contaminants in the breathing zone of surgical staff are measured, along with analyses of velocity, temperature, and humidity distribution in the patient's thermal plume. Negative pressure shows acceptable temperature and velocity variations according to the World Health Organization. Higher ACH and AC inlet velocities lead to decreased relative humidity and enhance heat removal efficiency, and air exchange efficiency. Contaminant removal, evaluated through the Contaminant Removal Effectiveness (CRE), exhibits superiority under high Air Conditioner AC inlet modes and increased ACH rates, recording values of 1.1 and 1.2. The study strongly recommends isolation rooms for respiratory patients in negative-pressure ventilated operating rooms to mitigate infection transmission risks to the surgical staff. [ABSTRACT FROM AUTHOR]

The novel coronavirus pandemic (COVID-19) has necessitated a global increase in the use of face masks to limit the airborne spread of the virus. The global demand for personal protective equipment has at times led to shortages of face masks for the public, therefore makeshift masks have become commonplace. The severe acute respiratory syndrome caused by coronavirus-2 (SARS-CoV-2) has a spherical particle size of ~97 nm. However, the airborne transmission of this virus requires the expulsion of droplets, typically ~0.6–500 µm in diameter (by coughing, sneezing, breathing, and talking). In this paper, we propose a face covering that has been designed to effectively capture SARS-CoV-2 whilst providing uncompromised comfort and breathability for the wearer. Herein, we describe a material approach that uses amorphous silica microspheres attached to cotton fibres to capture bioaerosols, including SARS CoV-2. This has been demonstrated for the capture of aerosolised proteins (cytochrome c, myoglobin, ubiquitin, bovine serum albumin) and aerosolised inactivated SARS CoV-2, showing average filtration efficiencies of ~93% with minimal impact on breathability. There has been a significant increase in the demand for face masks, but achieving a balance of breathability and effective filtration is challenging. Here, the authors report a face mask of modified cotton for the capture of bioaerosols. [ABSTRACT FROM AUTHOR]

The environment inside airliner cabins has attracted increasing attention. Instantaneous airflow, as one of the fundamental parameters of airflow field, affects aspects of the airliner cabin environment such as occupant comfort and airborne disease transmission. This study evaluated the characteristics of instantaneous airflow in airliner cabins with different ventilation systems (mixing ventilation and displacement ventilation) and focused on the region above passengers' heads, where complex turbulence characteristics are found. This investigation used ultrasonic anemometers for measurements at ten selected points above passengers' heads. The energy ratio on the low-frequency scale with mixing ventilation was greater than that with displacement ventilation. The instantaneous airflow with mixing ventilation was close to that of natural wind, while the instantaneous airflow with displacement ventilation was close to that of mechanical wind. Compared with mixing ventilation, displacement ventilation produced a smaller vortex length and a shorter residence time. Moreover, there was no long-term vortex in the flow field under displacement ventilation, and therefore, pollutants would be discharged more quickly from the cabin. In addition, this paper distinguishes the spatial and temporal turbulence scales of mixing and displacement ventilation, thus providing a reference for the selection of grid size and time steps in computational fluid dynamics simulations. [ABSTRACT FROM AUTHOR]

The emergence of SARS-CoV-2 virus mutations is a pressing concern in the context of the COVID-19 pandemic. In this paper, a Susceptible–Infected–Recovered (SIR) compartmental model has been formulated in terms of cellular automata and ordinary differential equations to simulate the transmission dynamics of a virus. This model accounts for the potential of new virus mutations to create additional infections of a multi-strain disease while also considering the impact of vaccination on disease control within a population. The basic reproduction number of the disease is derived, and the effect of virus mutations and vaccination rates is evaluated on a population over five years. The results of numerical simulations demonstrate the significant role of maintaining high vaccination rates in controlling the spread of the virus, even when assuming that all variants have similar illness characteristics and that a single shot of vaccine provides complete and lifelong protection against all strains. The findings underscore the necessity for countries to implement a consistent and high-level vaccination plan as soon as vaccines become available in order to mitigate the impact of a pandemic effectively. In conclusion, this study highlights the importance of taking into account the potential impact of virus mutations for controlling the COVID-19 pandemic. Furthermore, it emphasizes the critical role of vaccination in limiting the spread of the virus, and emphasizes the need to implement and maintain high vaccination rates as part of a comprehensive approach to managing the ongoing pandemic. [ABSTRACT FROM AUTHOR]

Heating, ventilation, and air conditioning (HVAC) systems play a crucial role in either increasing or decreasing the risk of airborne disease transmission. High ventilation, for instance, is a common method used to control and reduce the infection risk of airborne diseases such as COVID-19. On the other hand, high ventilation will increase energy consumption and cost. This paper proposes an optimal HVAC controller to assess the trade-off between energy consumption and indoor infection risk of COVID-19. To achieve this goal, a nonlinear model predictive controller (NMPC) is designed to control the HVAC systems of a university building to minimize the risk of COVID-19 transmission while reducing building energy consumption. The NMPC controller uses dynamic models to predict future outputs while meeting system constraints. To this end, a set of dynamic physics-based models are created to capture heat transfer and conservation of mass, which are used in the NMPC controller. Then, the developed models are experimentally validated by conducting experiments in the ETLC building at the University of Alberta, Canada. A classroom in the building is equipped with a number of sensors to measure indoor and outdoor environmental parameters such as temperature, relative humidity, and CO 2 concentration. The validation results show that the model can predict room temperature and CO 2 concentration by 0.8%, and 2.4% mean absolute average errors, respectively. Based on the validated models, the NMPC controller is designed to calculate the optimal airflow and supply air temperature for every 15 min. The results for real case studies show that the NMPC controller can reduce the infection risk of COVID-19 transmission below 1% while reducing energy consumption by 55% when compared to the existing building controller. [ABSTRACT FROM AUTHOR]

The global spread of the coronavirus disease 2019 (COVID-19) has increased the demand of effective control of the disease transmission between people, especially when they are in close distance between each other. The microenvironment between the people in short distance contains multiple airflow patterns that directly affect the disease transmission. By understanding and respecting this special localized environment, the airborne cross-infection at both short and long distance can be minimized. This paper gives an overview of the flow fields in human microenvironment. The exhalation flow from different respiratory activities, e.g. normal breathing, speaking, coughing or sneezing is considered as a part of the microenvironment. The dynamics of the exhalation flow and the contained droplets or aerosols are summarized from previous studies. The factors influencing the flow fields in human microenvironment are discussed, including both the physiological factors of the occupants and the environmental factors in the ventilated context (macroenvironment). Effective control of these influencing factors can be helpful to mitigate airborne transmission risk between individuals. This paper highlights the importance of better understanding of the dynamics and transmission routes of the expelled virus-laden droplets or aerosols, which are largely affected by complex flow interactions in human microenvironment. [ABSTRACT FROM AUTHOR]

Airborne transmission of infectious diseases through air travel has become a major concern, especially during the COVID‐19 pandemic. The flying public and crew members have long demanded better air quality and thermal comfort in commercial airliner cabins. This paper reviewed studies related to the airliner cabin air environment that have been published in scientific journals since 2000, to understand the state‐of‐the‐art in cabin air environment design and the efforts made to improve this environment. In this critical review, this paper discusses the challenges and opportunities in studying the cabin air environment. The literature review concluded that current environmental control systems for airliner cabins have done little to stop the airborne transmission of infectious diseases. There were no reports of significant air quality problems in cabins, although passengers and crew members have complained of some health‐related issues. The air temperature in cabins needs to be better controlled, and therefore, better thermal comfort models for airliners should be developed. Low humidity is a major complaint from passengers and crew members. Gaspers are used by passengers to adjust thermal comfort, but they do not improve air quality. Various personalized and displacement ventilation systems have been developed to improve air quality and thermal comfort. Air cleaning technologies need to be further developed. Good tools are available for designing a better cabin air environment. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editors discuss various reports within the issue on topics including airborne infection in health facilities, computational fluid dynamics, and ultraviolet germicidal irradiation.

Ventilation systems are one of the most effective strategies to reduce the risk of viral infection transmission in buildings. However, insufficient ventilation rates in crowded spaces, such as schools, would lead to high risks of infection transmission. On the other hand, excessive ventilation rates might significantly increase cooling energy consumption. Therefore, energy-efficient control methods, such as Demand Control Ventilation systems (DCV), are typically considered to maintain acceptable indoor air quality. However, it is unclear if the DCV-based controls can supply adequate ventilation rates to minimize the probability of infection (POI) in indoor spaces. This paper investigates the benefits of optimized ventilation strategies, including conventional mechanical systems (MV) and DCV, in reducing the POI and cooling energy consumption through a detailed sensitivity analysis. The study also evaluates the impact of the ventilation rate, social distancing, and number of infectors on the performance of the ventilation systems. A coupling approach of a calibrated energy model of a school building in Jeddah, KSA, with a validated Wells–Riley model is implemented. Based on the findings of this study, proper adjustment of the DCV set point is necessary to supply adequate ventilation rates and reduce POI levels. Moreover, optimal values of 2 ACH for ventilation rate and 2 m for social distance are recommended to deliver acceptable POI levels, cooling energy use, and indoor CO2 concentration for the school building. Finally, this study confirms that increasing the ventilation rate is more effective than increasing social distancing in reducing the POI levels. However, this POI reduction is achieved at the cost of a higher increase in the cooling energy. [ABSTRACT FROM AUTHOR]

The COVID-19 pandemic raised public awareness about airborne particulate matter (PM) due to the spread of infectious diseases via the respiratory route. The persistence of potentially infectious aerosols in public spaces and the spread of nosocomial infections in medical settings deserve careful investigation; however, a systematic approach characterizing the fate of aerosols in clinical environments has not been reported. This paper presents a methodology for mapping aerosol propagation using a low-cost PM sensor network in ICU and adjacent environments and the subsequent development of the data-driven zonal model. Mimicking aerosol generation by a patient, we generated trace NaCl aerosols and monitored their propagation in the environment. In positive (closed door) and neutral-pressure (open door) ICUs, up to 6% or 19%, respectively, of all PM escaped through the door gaps; however, the outside sensors did not register an aerosol spike in negative-pressure ICUs. The K-means clustering analysis of temporospatial aerosol concentration data suggests that ICU can be represented by three distinct zones: (1) near the aerosol source, (2) room periphery, and (3) outside the room. The data suggests two-phase plume behavior: dispersion of the original aerosol spike throughout the room, followed by an evacuation phase where "well-mixed" aerosol concentration decayed uniformly. Decay rates were calculated for positive, neutral, and negative pressure operations, with negative-pressure rooms clearing out nearly twice as fast. These decay trends closely followed the air exchange rates. This research demonstrates the methodology for aerosol monitoring in medical settings. This study is limited by a relatively small data set and is specific to single-occupancy ICU rooms. Future work needs to evaluate medical settings with high risks of infectious disease transmission. [ABSTRACT FROM AUTHOR]

This paper presents the numerical results of particle propagation in open space, taking into account the temperature of the human body and the surface of the ground. And also, the settling of particles or droplets under the action of gravitational force and transport in the open air is taken into account, taking into account the temperature during the process of breathing and sneezing or coughing. The temperature of the body and the surface of the ground, different rates of particle emission from the mouth, such as breathing and coughing or sneezing, are numerically investigated. The effect of temperature, cross-inlet wind, and the velocity of particle ejection from a person's mouth on social distancing is being investigated using a numerical calculation. The variable temperature of the human body forms a thermal plume, which affects the increase in the trajectory of the particle propagation, taking into account the lateral air flow. The thermal plume affects the particles in the breathing zone and spreads the particles over long distances in the direction of the airflow. The result of this work shows that in open space, taking into account the temperature of the body and the surface of the ground, a 2-m social distance may be insufficient for the process of sneezing and social distance must be observed depending on the breathing mode. [ABSTRACT FROM AUTHOR]

The COVID-19 pandemic highlighted the importance of indoor air quality (IAQ) and ventilation, which researchers have been warning about for years. During the pandemic, researchers studied several indicators using different approaches to assess IAQ and diverse ventilation systems in indoor spaces. To provide an overview of these indicators and approaches in the case of airborne transmission through aerosols, we conducted a literature review, which covered studies both from before and during the COVID-19 pandemic. We searched online databases for six concepts: aerosol dispersion, ventilation, air quality, schools or offices, indicators, and assessment approaches. The indicators found in the literature can be divided into three categories: dose-, building-, and occupant-related indicators. These indicators can be measured in real physical spaces, in a controlled laboratory, or modeled and analyzed using numerical approaches. Rather than organizing this paper according to these approaches, the assessment methods used are grouped according to the following themes they cover: aerosol dispersion, ventilation, infection risk, design parameters, and human behavior. The first finding of the review is that dose-related indicators are the predominant indicators used in the selected studies, whereas building- and occupant-related indicators are only used in specific studies. Moreover, for a better understanding of airborne transmission, there is a need for a more holistic definition of IAQ indicators. The second finding is that although different design assessment tools and setups are presented in the literature, an optimization tool for a room's design parameters seems to be missing. Finally, to efficiently limit aerosol dispersion in indoor spaces, better coordination between different fields is needed. [ABSTRACT FROM AUTHOR]

Air purifiers are limited to small polluting airborne particles and poor air circulation (fan) for bringing airborne particles inside the device. Thus, the optimal utility of domestic air purifiers (DAPs) for eliminating airborne viruses is still ambiguous. This paper addresses the above limitations using computational fluid dynamics modeling and simulations to investigate the optimal local design of a DAP in an indoor space. We also investigate the integrated fan system and the local transport of airborne viruses. Three different scenarios of using standard DAP equipment (144 m 3 / h) are explored in an indoor space comprising a furnished living room 6 × 6 × 2.5 m 3 . We show that the local positioning of a purifier indoors and the fan system embedded inside it can significantly alter the indoor airborne virus transmission risk. Finally, we propose a new indoor air circulation system that better ensures indoor airborne viruses' local orientation more efficiently than a fan embedded in a standard DAP. [ABSTRACT FROM AUTHOR]

The year 2020 has seen the world gripped by the effects of the COVID‐19 pandemic. It is not the first time, nor will it be last, that our increasingly globalized world has been significantly affected by the emergence of a new disease. In much of the Northern Hemisphere, the academic year begins in September, and for many countries, September 2020 marked the return to full schooling after some period of enforced closure due to COVID‐19. In this paper, we focus on the airborne spread of disease and investigate the likelihood of transmission in school environments. It is crucial to understand the risk airborne infection from COVID‐19 might pose to pupils, teachers, and their wider social groups. We use monitored CO2 data from 45 classrooms in 11 different schools from within the UK to estimate the likelihood of infection occurring within classrooms regularly attended by the same staff and pupils. We determine estimates of the number of secondary infections arising via the airborne route over pre/asymptomatic periods on a rolling basis. Results show that, assuming relatively quiet desk‐based work, the number of secondary infections is likely to remain reassuringly below unity; however, it can vary widely between classrooms of the same school even when the same ventilation system is present. Crucially, the data highlight significant variation with the seasons with January being nearly twice as risky as July. We show that such seasonal variations in risk due to changes in ventilation rates are robust and our results hold for wide variations in disease parameterizations, suggesting our results may be applied to a number of different airborne diseases. [ABSTRACT FROM AUTHOR]

The World Health Organization has pointed out that airborne transmission via aerosol particles can be a strong vector for the spread of SARS-CoV-2. Protecting occupants from infectious diseases or harmful particulate matter (PM) in general can be challenging. While experimentally outlining the detailed flow of PM in rooms may require complex setups, computational fluid dynamics (CFD) simulations can provide insights into improving the safety of the built environment and the most effective positioning of air-purifying devices. While previous studies have typically leveraged Reynolds-averaged Navier–Stokes (RANS) approaches for predicting particle propagation, the turbulence length scales accurately captured in these simulations may not be sufficient to provide a realistic spread and the mixing of particles under the effects of forced convection. In this paper, we experimentally validate a Lattice Boltzmann very large eddy simulation (VLES) approach including particle modeling. We also demonstrate how this simulation approach can be used to improve the effectiveness of air filtration devices in realistic office environments. [ABSTRACT FROM AUTHOR]

Aerosol droplets made from respiratory liquid are of fundamental importance for airborne transmission of several virus-based diseases, such as COVID-19. While the transmission route in the air has been intensively studied in the last two years, only few papers deal with the formation of these droplets. It seems to be accepted that such droplets are generated by upper airway activity such as talking, sneezing, or coughing. Especially talking is associated with disease transmission, although the droplet formation mechanisms have not been fully resolved yet. Thus, we focus on the investigation of the atomization process of respiratory liquid attached to the vocal folds. A new experimental setup has been installed that emulates the vocal folds and their oscillating movement in a simplified manner. A model liquid mimicking the respiratory mucus is dispersed at the vocal folds. The primary atomization of the model liquid into an air stream is observed qualitatively. This new insight shows that in contrast to the typical assumption that only liquid bridges form between the vocal folds and breakup into droplets, rather bubbles are generated, which can breakup into much smaller particles than filaments. Furthermore, droplet size distributions downstream of the vocal folds are evaluated. The influence of the oscillation frequency and amplitude as well as air flow rate on the droplet size distributions are analyzed. It is found that an increase in both frequency and amplitude leads to smaller particle sizes, while raising the air flow rate results in a higher proportion of larger particles. [ABSTRACT FROM AUTHOR]

An indoor environment in a hospital building requires a high indoor air quality (IAQ) to overcome patients' risks of getting wound infections without interrupting the recovery process. However, several problems arose in obtaining a satisfactory IAQ, such as poor ventilation design strategies, insufficient air exchange, improper medical equipment placement and high door opening frequency. This paper presents an overview of various methods used for assessing the IAQ in hospital facilities, especially in an operating room, isolation room, anteroom, postoperative room, inpatient room and dentistry room. This review shows that both experimental and numerical methods demonstrated their advantages in the IAQ assessment. It was revealed that both airflow and particle tracking models could result in different particle dispersion predictions. The model selection should depend on the compatibility of the simulated result with the experimental measurement data. The primary and secondary forces affecting the characteristics of particle dispersion were also discussed in detail. The main contributing forces to the trajectory characteristics of a particle could be attributed to the gravitational force and drag force regardless of particle size. Meanwhile, the additional forces could be considered when there involves temperature gradient, intense light source, submicron particle, etc. The particle size concerned in a healthcare facility should be less than 20 μm as this particle size range showed a closer relationship with the virus load and a higher tendency to remain airborne. Also, further research opportunities that reflect a more realistic approach and improvement in the current assessment approach were proposed. [ABSTRACT FROM AUTHOR]

A close correlation between CO2 concentration and aerosol enables the wide utilization of CO2 concentration as a good representation of Severe Acute Respiratory Syndrome-Coronavirus-2 infection airborne transmission. On the other side, many indoor air-quality monitoring devices have been developed for indoor monitoring applications. However, most of them are multiparameter air-quality sensor systems and tend to consume relatively high power, are relatively large devices, and are fairly expensive; therefore, they not meet the requirement for indoor monitoring applications. This paper presents a smart wireless sensor node that can measure and monitor CO2 concentration levels. The node was designed to meet the requirements of indoor air-quality monitoring applications by considering several factors, such as compact size, low cost, and low power, as well as providing real-time, continuous, reliable, and remote measurement. Furthermore, the commercial off-the-shelf and low-power consumption components are chosen to fit with the low-cost development and reduce energy consumption. Moreover, a low-power algorithm and cloud-based data logger also were applied to minimize the total power consumption. This power strategy was applied as a preliminary development toward an autonomous sensor node. The node has a compact size and consumes low energy for one cycle of CO2 measurement, accompanied by high accuracy with very low measurement error. The experiment result revealed the node could measure and monitor in real-time continuous, reliable, and remote CO2 concentration levels in indoor and outdoor environments. A user interface visualizes CO2 concentration graphically and numerically using the Adafruit platform for easy accessibility over the Internet of Things. The developed node is very promising and suitable for indoor CO2 monitoring applications with the acquired data that could be utilized as an indicator to minimize the risk of indoor Severe Acute Respiratory Syndrome-Coronavirus-2 airborne transmission. [ABSTRACT FROM AUTHOR]

Event-based surveillance (EBS) gathers information from a variety of data sources, including online news articles. Unlike the data from formal reporting, the EBS data are not structured, and their interpretation can overwhelm epidemic intelligence (EI) capacities in terms of available human resources. Therefore, diverse EBS systems that automatically process (all or part of) the acquired nonstructured data from online news articles have been developed. These EBS systems (e.g., GPHIN, HealthMap, MedISys, ProMED, PADI-web) can use annotated data to improve the surveillance systems. This paper describes a framework for the annotation of epidemiological information in animal disease-related news articles. We provide annotation guidelines that are generic and applicable to both animal and zoonotic infectious diseases, regardless of the pathogen involved or its mode of transmission (e.g., vector-borne, airborne, by contact). The framework relies on the successive annotation of all the sentences from a news article. The annotator evaluates the sentences in a specific epidemiological context, corresponding to the publication date of the news article. Measurement(s) Precision/Recall • Annotator aggreement Technology Type(s) Expert annotation • Kappa's coefficient • Natural Language Processing Sample Characteristic - Organism Animal • African swine fever virus • Avian influenza • Foot-and-mouth disease virus • Bluetongue virus • Bovine spongiform encephalopathy Sample Characteristic - Environment Animal infectious diseases [ABSTRACT FROM AUTHOR]

Airborne infection isolation (AII) rooms are used to accommodate patients with highly infectious diseases and keep the released pathogens to limit the risk of cross-infection. This paper proposes a concept for an AII room made from two shipping containers to handle the scarcity of hospital beds when the COVID-19 disease spreads over the world. The proposed system consists of the main isolation room, anteroom, and toilet as well as other functional areas. In addition, the main isolation room was modeled with important components such as a supply air vent, exhaust air, a patient, and a bed. The computational fluid dynamics (CFD) approach based on the finite volume method (FVM) is used to solve the three-dimensional governing equations. The CO2 concentration was used to determine the infectious contaminant concentration of the air in the room. Therefore, the infectious control could be evaluated by the air change per hour (ACH). The numerical results show that the room temperature is maintained at 24°C, which is appropriate for people in the room. The laminar airflow extends downward to the floor after leaving the supply air vent on the ceiling, creating circulating patterns throughout the room. When evaluating the effectiveness of ventilation systems to remove airborne contaminants based on different ACH numbers, the CO2 concentration in the room was reduced to 581 ppm, 477 ppm, and 438 ppm in the cases of 12 ACH, 24 ACH, and 48 ACH, respectively. As a result, the greater the number of air change per hour, the greater the performance for contaminant removal. It served as the foundation for assessing and optimizing the ventilation system of the portable negative pressure room. [ABSTRACT FROM AUTHOR]

Featured Application: Periodic ventilation can be a useful strategy for reducing the risk of any airborne transmitted disease. It is particularly well-suited for naturally ventilated environments in cold weathers, as it allows for a compromise between IAQ and thermal comfort, and does not require any modification to existing buildings. The importance of Indoor Air Quality (IAQ) has been highlighted by the COVID-19 pandemic, particularly due to the possibility of long-distance airborne transmission. Consequently, assessment of ventilation rates and estimation of infection risk has become a matter of the utmost importance. In this paper, a naturally ventilated elementary school classroom is studied, where carbon dioxide ( CO 2 ) concentrations were measured during five months. Ventilation rates are calculated via a fully-mixed box model and the airborne risk of infection for SARS-CoV-2 is assessed. Risk results are found to steadily decline from winter to spring. Furthermore, analytical simulations for different scenarios are conducted. It is shown that periodic ventilation significantly reduces the transmission risk, even if it occurs only during very reduced time spans. The results show that periodic ventilation is a useful strategy for reducing the risk of any airborne transmitted disease. It is particularly well-suited for naturally ventilated environments in cold weathers, as it allows for a compromise between IAQ and thermal comfort, and does not require any modification to existing buildings. [ABSTRACT FROM AUTHOR]

Infectious aerosol dispersion poses significant infection risks (i.e., COVID-19) in classrooms due to dense and long occupancy. Natural ventilation is an effective strategy to reduce airborne infection transmission. The building-related parameters, particularly openings, determine the natural ventilation effectiveness in reducing contaminant dispersion, necessitating an inquiry due to complex dispersion and airflow patterns. This paper investigates the correlation between window height, natural ventilation, and COVID-19 dispersion. A simulation pipeline involving a parametric 3D design environment, computational fluid dynamics (CFD), and energy simulations is developed and implemented on nine design scenarios representing different inlet-outlet heights of a free-running (no heating, cooling or mechanical ventilation) classroom. The inlet height and the inlet-outlet height difference have a considerable impact on indoor infection risk confirming that stack ventilation and the Bernoulli effect decrease indoor contaminant concentration. Proximity to openings does not ensure lower contamination levels. Proximity to the contaminant does not result in higher contamination levels. [ABSTRACT FROM AUTHOR]

Laboratory data suggest that coronavirus (Covid 19) can spread from infected people to other people through airborne transmission. In this paper, we want to explain this phenomenon with quantum gravitational effects as a minimal measurable momentum. We will show that when virus droplets (which have velocities) propagate from a specific source (e.g., coughing, sneezing, or talking), they remain suspended in spacetime due to the existence of a minimal measurable momentum. Because the momentum of these particles is never zero in this situation. In this regard, we solve equations of motion in the presence of a minimal measurable momentum for virus-carrying particles and we obtain trajectories of them in the phase space. [ABSTRACT FROM AUTHOR]

This study deals with the pollution impact of biomedical waste (BMW) generation due to the COVID-19 pandemic at both the global and national levels. This discussion is important in light of clear scientific evidence that, apart from the airborne transmission of the disease, the virus also survives on different surfaces and poses the risk of infection. Moreover, an investigation is conducted on BMW generation in tons/day in India during the COVID-19 period, with implications for future projection. Additionally, a pioneering study was conducted to estimate the usage of facemasks during the COVID-19 pandemic in India. This paper also provides a feasible solution, by adopting a modern perspective, towards managing BMW generated in the context of SARS-CoV-2 at isolation wards and crematoriums. Strategical approaches have been suggested for segregating and safely disposing BMW. The latest availability of disposal facilities is discussed based on source data provided by the Central Pollution Control Board (CPCB), India. Among the many disposal methods, incineration technologies are examined in depth. The impact of existing incineration technology on the environment and human health has been extensively studied. This study suggests strategies for controlling BMW generation during the COVID-19 pandemic. [ABSTRACT FROM AUTHOR]

The present paper investigates droplet and aerosol emission from the human respiratory function by numerical and experimental methods, which is analyzed at the worst-case scenario, a violent sneeze without a face covering. The research findings develop the understanding of airborne disease transmission relevant to COVID-19, its recent variants, and other airborne pathogens. A human sneeze is studied using a multiphase Computational Fluid Dynamics (CFD) model using detached eddy simulation coupled to the emission of droplets that break up, evaporate, and disperse. The model provides one of the first experimental benchmarks of CFD predictions of a human sneeze event. The experiments optically capture aerosols and droplets and are processed to provide spatiotemporal data to validate the CFD model. Under the context of large random uncertainty, the studies indicate the reasonable correlation of CFD prediction with experimental measurements using velocity profiles and exposure levels, indicating that the model captures the salient details relevant to pathogen dispersion. Second, the CFD model was extended to study the effect of relative humidity with respect to the Wells curve, providing additional insight into the complexities of evaporation and sedimentation characteristics in the context of turbulent and elevated humidity conditions associated with the sneeze. The CFD results indicated correlation with the Wells curve with additional insight into features, leading to non-conservative aspects associated with increased suspension time. These factors are found to be associated with the combination of evaporation and fluid-structure-induced suspension. This effect is studied for various ambient air humidity levels and peaks for lower humidity levels, indicating that the Wells curve may need a buffer in dry climates. Specifically, we find that the increased risk in dry climates may be up to 50% higher than would be predicted using the underlying assumptions in Wells' model. [ABSTRACT FROM AUTHOR]

The COVID-19 pandemic of 2020–2022 has revealed the vulnerability of modern society to a highly contagious airborne virus. Many spaces in the urban and built environment designed during the late twentieth and early twenty-first century are ill-suited to maintain the level of social distancing required to reduce the probability of virus transmission. Enclosed spaces—in particular, communal circulation spaces such as corridors, elevators and lobbies—have proven loci of transmission, together with circulating reticulated air and lack of proper ventilation. While urban planning needs to incorporate the lessons learnt during COVID-19 in order to future-proof our communities through the provision of well-designed greenspaces, the main burden will fall on architects, who will play an instrumental role in designing buildings that are fit-for purpose. This conceptual paper reviews the status quo and discusses a number of strategies to future-proof human habitation for the inevitable next pandemic. [ABSTRACT FROM AUTHOR]

Indoor carbon dioxide (CO2) concentrations have been considered for decades in evaluating indoor air quality (IAQ) and ventilation, and more recently in discussions of the risk of airborne infectious disease transmission. However, many of these applications reflect a lack of understanding of the connection between indoor CO2 levels, ventilation, and IAQ. For example, a single indoor concentration such as 1000 ppmv is often used as a metric of IAQ and ventilation without an understanding of the significance of this or any other value. CO2 concentrations are of limited value as IAQ metrics, and a single concentration will not serve as a ventilation indicator for spaces with different occupancies and ventilation requirements. An approach has been developed to estimate a space‐specific CO2 level that can serve as a metric of outdoor ventilation rates. The concept is to estimate the CO2 concentration that would be expected in a specific space given its intended or expected ventilation rate, the number of occupants, the rate at which they generate CO2, and the time that has transpired since the space was occupied. This paper describes the approach and presents example calculations for several commercial, institutional, and residential occupancies. [ABSTRACT FROM AUTHOR]

Aerosol transmission constitutes one of the major transmission routes of the SARS-CoV-2 pathogen. Due to the pathogen's properties, research on its airborne transmission has some limitations. This paper focuses on silica nanoparticles (SiO2) of 40 and 200 nm sizes as the physicochemical markers of a single SARS-CoV-2 particle enabling experiments on the transmission of bioaerosols in public spaces. Mixtures of a determined silica concentration were sprayed on as an aerosol, whose particles, sedimented on dedicated matrices, were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Since it was not possible to quantitatively identify the markers based on the obtained images, the filters exposed with the AirSampler aspirator were analyzed based on inductively coupled plasma optical emission spectroscopy (ICP-OES). The ICP-OES method enabled us to determine the concentration of silica after extracting the marker from the filter, and consequently to estimate the number of markers. The developed procedure opens up the possibility of the quantitative estimation of the spread of the coronavirus, for example in studies on the aerosol transmission of the pathogen in an open environment where biological markers—surrogates included—cannot be used. [ABSTRACT FROM AUTHOR]