Airborne Transmission Of Virus Research Articles

The effects of ventilation layout on cough droplet dynamics relating to seasonal influenza

The primary aim of this paper is to investigate airborne virus transmission in a typical meeting room relating to the heating, ventilation, and air conditioning (A.C.) systems. While the installation of 4-way cassette A.C. systems in offices and meeting rooms has become increasingly common, their efficiency in mitigating short-range airborne virus spread remains poorly understood. Addressing this gap is critical in the post-pandemic era, where understanding the limitations of various ventilation systems is paramount for public health. We systematically compare the performance of the 4-way cassette A.C., various configurations of mixing and displacement ventilation systems, and natural ventilation in controlling the spread of respiratory viruses. Our research uniquely integrates evaporation models to accurately simulate cough clouds' multiphase behavior under both quiescent and thermally influenced conditions. The study benchmarks these systems against two widely recognized ventilation standards (i.e., 5 air changes per hour and 10 l/s per person), offering evidence-based insights applicable across diverse indoor settings. Our findings reveal significant thermal effects in the quiescent case, resulting in 32.3%, 54.3%, and 8.0% changes in the axial, vertical, and lateral spread of the virus-laden droplets, respectively. Notably, the 0.5 m/s 4-way cassette A.C. system demonstrated superior performance, reducing the axial spread by 29.6% compared to other mechanical ventilation configurations. Furthermore, the role of exhaust outlets or doors was found to be critical in shaping the spread pattern in natural ventilation scenarios. This work can offer practical guidance to office workers, engineers, and public health officials on enhancing indoor airborne infection control.

Dependence of aerosol-borne influenza A virus infectivity on relative humidity and aerosol composition.

We describe a novel biosafety aerosol chamber equipped with state-of-the-art instrumentation for bubble-bursting aerosol generation, size distribution measurement, and condensation-growth collection to minimize sampling artifacts when measuring virus infectivity in aerosol particles. Using this facility, we investigated the effect of relative humidity (RH) in very clean air without trace gases (except ∼400 ppm CO2) on the preservation of influenza A virus (IAV) infectivity in saline aerosol particles. We characterized infectivity in terms of 99%-inactivation time, t 99, a metric we consider most relevant to airborne virus transmission. The viruses remained infectious for a long time, namely t 99 > 5 h, if RH < 30% and the particles effloresced. Under intermediate conditions of humidity (40% < RH < 70%), the loss of infectivity was the most rapid (t 99 ≈ 15-20 min, and up to t 99 ≈ 35 min at 95% RH). This is more than an order of magnitude faster than suggested by many previous studies of aerosol-borne IAV, possibly due to the use of matrices containing organic molecules, such as proteins, with protective effects for the virus. We tested this hypothesis by adding sucrose to our aerosolization medium and, indeed, observed protection of IAV at intermediate RH (55%). Interestingly, the t 99 of our measurements are also systematically lower than those in 1-μL droplet measurements of organic-free saline solutions, which cannot be explained by particle size effects alone.

Multi-scenario surveillance of respiratory viruses in aerosols with sub-single-copy spatial resolution

Highly sensitive airborne virus monitoring is critical for preventing and containing epidemics. However, the detection of airborne viruses at ultra-low concentrations remains challenging due to the lack of ultra-sensitive methods and easy-to-deployment equipment. Here, we present an integrated microfluidic cartridge that can accurately detect SARS-COV-2, Influenza A, B, and respiratory syncytial virus with a sensitivity of 10 copies/mL. When integrated with a high-flow aerosol sampler, our microdevice can achieve a sub-single-copy spatial resolution of 0.83 copies/m3 for airborne virus surveillance with an air flow rate of 400 L/min and a sampling time of 30 minutes. We then designed a series of virus-in-aerosols monitoring systems (RIAMs), including versions of a multi-site sampling RIAMs (M-RIAMs), a stationary real-time RIAMs (S-RIAMs), and a roaming real-time RIAMs (R-RIAMs) for different application scenarios. Using M-RIAMs, we performed a comprehensive evaluation of 210 environmental samples from COVID-19 patient wards, including 30 aerosol samples. The highest positive detection rate of aerosol samples (60%) proved the aerosol-based SARS-CoV-2 monitoring represents an effective method for spatial risk assessment. The detection of 78 aerosol samples in real-world settings via S-RIAMs confirmed its reliability for ultra-sensitive and continuous airborne virus monitoring. Therefore, RIAMs shows the potential as an effective solution for mitigating the risk of airborne virus transmission.

Research on natural ventilation of a community library related to epidemiological insight by using CFD simulation method

Abstract Spreading through airflow is one of the most common routes for the transmission of viruses, which may result in serious public health problems. To acquire a healthy space for the community library, designing a reasonable ventilation system is a vital measure which can reduce the risk of transmission of the virus effectively. The purpose of this research is to study natural ventilation methods in an epidemiological insight for the design of a healthy community library by using computational fluid dynamics (CFD) software SOLIDWORKS Flow Simulation. Five typical opening types of windows were selected and studied in the research on the ventilation of the yoga room of a community library, with airflow evaluated by the ACH method, so as to search for the most suitable window type to avoid airborne virus transmission. The results acquired by SOLIDWORKS simulation showed that 75%, 90%, and 100% openings corresponding to Jalousie, casement, and double casement window types respectively are optimal in community space. The natural ventilation design by proper windows can be applied in the community library and other public spaces.

Guidelines for Conducting Worship During Epidemic Transmission According to Islamic and Scientific Perspectives

The Coronavirus is a large family of viruses that cause illnesses ranging from the common cold to more severe diseases. COVID-19 is an infectious disease caused by the novel coronavirus (SARS-CoV-2). The government has issued guidelines to control the spread of the virus, including matters involving activities in mosques such as the implementation of prayer rituals. Some laws and practices in the prayer rituals, issued by the mufti and religious departments, initially caused confusion among the Muslim community because such matters had never occurred in Malaysia and there was a lack of explanation by religious experts. Thus, this study is conducted to obtain views from a panel of experts on matters that can be improved and enhanced in these guidelines. This study employs the method of focus group discussions (FGD) involving 6 expert panelists from the fields of religion, science, and medicine. All expert panelists agree that the development of these guidelines is very beneficial for the community to refer to in the event of airborne virus transmission such as COVID-19 in the future. These guidelines provide justification from both Islamic and scientific perspectives to make the community more confident and comfortable in practicing them.

Resolving the Loss of Intermediate-Size Speech Aerosols in Funnel-Guided Particle Counting Measurements

Modeling of airborne virus transmission and protection against it requires knowledge of the amount of biofluid emitted into the atmosphere and its viral load. Whereas viral concentrations in biofluids are readily measured by quantitative PCR, the total volume of fluids aerosolized during speaking, as measured by different researchers using various technologies, differs by several orders of magnitude. We compared collection methods in which the aerosols first enter into a low-humidity chamber either by direct injection or via commonly used funnel and tubing arrangements, followed by standard optical particle sizer measurement. This “collect first, measure later” approach sacrifices the recording of the temporal correlation between aerosol generation and sound types such as plosives and vowels. However, the direct-injection mode prevents inertia deposition associated with the funnel arrangements and reveals far more intermediate-size (5–20 μm in diameter) particles that can dominate the total mass of ejected respiratory aerosol. The larger aerosol mass observed with our method partially reconciles the large discrepancy between the SARS-CoV-2 infectious dose estimated from superspreader event analyses and that from human challenge data. Our results also impact measures to combat airborne virus transmission because they indicate that aerosols that settle faster than good room ventilation rates can dominate this process.

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.

The potential of construction robotics to reduce airborne virus transmission in the construction industry in the UK and China

This paper aims to identify construction robotics' potential to reduce airborne virus transmission, review factors limiting the technology's adoption and highlight how similar barriers have been addressed in other industries. Construction robotics were identified and classified into 8 themes with 25 categories through a critical literature review. We undertook interviews with 4 construction contractors and conducted an online questionnaire with 32 experts from the UK (n=14) and China (n=18) who reviewed the robotic systems we identified and ranked the potential ability of each to reduce airborne virus transmission within the construction industry. The results of this study showed that construction robotics is not only beneficial to reduce airborne virus transmission, but may also help to reduce the spread of future contagious viruses. We found no significant difference (P>0.05) in practical usage and implementation barriers to construction robotics between the UK and China. Cost, training and limited awareness of robotic technologies were the main implementation barriers we identified in both countries. Both the UK and China may need to adopt strategies such as providing more financial support to small construction industries and skill training which are utilised successfully in other sectors to realise the potential of construction robotic technologies.

Towards optimal design of patient isolation units in emergency rooms to prevent airborne virus transmission: From computational fluid dynamics to data-driven modeling

BackgroundPatient isolation units (PIUs) can be an effective method for effective infection control. Computational fluid dynamics (CFD) is commonly used for PIU design; however, optimizing this design requires extensive computational resources. Our study aims to provide data-driven models to determine the PIU settings, thereby promoting a more rapid design process. MethodUsing CFD simulations, we evaluated various PIU parameters and room conditions to assess the impact of PIU installation on ventilation and isolation. We investigated particle dispersion from coughing subjects and airflow patterns. Machine-learning models were trained using CFD simulation data to estimate the performance and identify significant parameters. ResultsPhysical isolation alone was insufficient to prevent the dispersion of smaller particles. However, a properly installed fan filter unit (FFU) generally enhanced the effectiveness of physical isolation. Ventilation and isolation performance under various conditions were predicted with a mean absolute percentage error of within 13%. The position of the FFU was found to be the most important factor affecting the PIU performance. ConclusionData-driven modeling based on CFD simulations can expedite the PIU design process by offering predictive capabilities and clarifying important performance factors. Reducing the time required to design a PIU is critical when a rapid response is required.

Direct numerical simulations of a novel device to fight airborne virus transmission

The SARS-CoV-2 (COVID-19) pandemic has highlighted the crucial role of preventive measures in avoiding the spread of disease and understanding the transmission of airborne viruses in indoor spaces. This study focuses on a novel personal protective equipment consisting of a fan-peaked cap that creates a jet flow of air in front of the individual's face to reduce the concentration of airborne viruses and decrease the risk of infection transmission. Direct numerical simulation is used to analyze the effectiveness of the device under certain conditions, such as the velocity of the airflow, flow orientation, ambient conditions, and geometrical factors.

The effects of ventilation conditions on mitigating airborne virus transmission

The effects of ventilation strategies on mitigating airborne virus transmission in a generic indoor space representative of a lobby area or information desk found in a hotel, company, or cruise ship are presented. Multiphase computational fluid dynamics simulations are employed in conjunction with evaporation modeling. Four different ventilation flow rates are examined based on the most updated post-COVID-19 pandemic standards from health organizations and recent findings from research studies. Three air changes per hour provide the best option for minimizing droplet spreading at reasonable energy efficiency. Thus, a higher ventilation rate is not the best solution to avoid spreading airborne diseases. Simultaneous coughing of all occupants revealed that contagious droplets could be trapped in regions of low airflow and on furniture, significantly prolonging their evaporation time. Multiphase flow simulations can help define ventilation standards to reduce droplet spreading and mitigate virus transmission while maintaining adequate ventilation with lower energy consumption. The present work significantly impacts how heat, air-conditioning, and ventilation systems are designed and implemented.

Reconfigurable sonic crystals with built-in Helmholtz's resonators for noise mitigation

Natural ventilation is desirable for improving the air quality against airborne transmission of viruses. On the other hand, a good noise barrier would not have any opening for effective noise mitigation as noise can enter the space with the natural ventilation. The use of noise shields and noise barriers for shielding a piece of noisy machine may also drastically cut down the natural ventilation which will be required for preventing heat built-up in the engine room. In this paper, acoustic metamaterials in the form of sonic crystals with built-in Helmholtz's resonators are designed for targeting the mitigation of mid to low frequency noise. The designs can be made reconfigurable with different distribution of sonic crystal elements. These sonic crystals are designed to target noise of different frequencies and also to provide sufficient structural support for large scale implementation. The designs can be used for providing a quieter corner for the occupants within a noisy environment, or to confine the noise from a machine or process within the sonic crystals.

AI-Driven Design System for Fabrication of Inhalable Nanocatchers for Virus Capture and Neutralization.

The global pandemic presents a critical threat to humanity, with no effective rapid-response solutions for early-stage virus dissemination. This study aims to create an AI-driven entry-blocker design system(AIEB) to fabricate inhalable virus-like nanocatchers (VLNCs) fused with entry-blocking peptides (EBPs) to counter pandemic viruses and explore therapeutic applications. This work focuses on developing angiotensin-converting enzyme 2 (ACE2)-mimic domain-fused VLNCs (ACE2@VLNCs) using AIEB and analyzing their interaction with the SARS-CoV-2 receptor binding domain (RBD), demonstrating their potential to hinder SARS-CoV-2 infection. Aerosol-based tests show ACE2@VLNCs persist over 70 min in the air and neutralize pseudoviruses within 30 min, indicating their utility in reducing airborne virus transmission. In vivo results reveal ACE2@VLNCs mitigate over 67% of SARS-CoV-2 infections. Biosafety studies confirm their safety, causing no damage to eyes, skin, lungs, or trachea, and not eliciting significant immune responses. These findings offer crucial insights into pandemic virus prevention and treatment, highlighting the potential of the ACE2@VLNCs system as a promising strategy against future pandemics.

Indoor acoustic quality of educational buildings in South West Europe: Influence of current ventilation strategies

The quality of the classroom environment has a great impact on the physical and mental health of students and teachers. The COVID-19 pandemic has highlighted the need for new measures and ventilation strategies to be implemented in educational buildings, to ensure indoor air quality in classrooms and to minimise the risk of airborne virus transmission. However, these ventilation protocols can influence the acoustic quality of classrooms and negatively affect students’ speech perception and learning performance. This study presents the results obtained from a field measurement campaign carried out to assess the acoustic characteristics of classrooms of the Fuentenueva Campus (University of Granada) and Azurém Campus (University of Minho). Different ventilation operating scenarios (active and inactive) were assessed to evaluate their impact on the indoor acoustic conditions. The reverberation time (RT), the only parameter used in both countries' regulations to assess acoustic conditions, was found to be higher on both campuses than the RT limits values. Comparison of the measured Speech Transmission Index (STI) and background noise values in the active and inactive ventilation scenario showed a clear variation of the indoor acoustic conditions. The background noise was higher in the active ventilation scenarios (40–57 dBA) than in the inactive ventilation scenarios (34–48 dBA). The average STI values obtained on both campuses for the inactive and active scenarios were 0.54 and 0.51, respectively. In some classrooms an STI difference of 0.1 was found between scenarios. The results obtained in this study provide a broader understanding of the acoustic conditions in university classrooms in Spain and Portugal. The results evidence the need of consider the synergies between the indoor acoustic and air quality conditions to ensure both: the spaces are safe and the acoustic conditions do not interfere with students' learning. The findings show that compliance with the current RT requirements does not ensure that classroom acoustic conditions do not interfere with student performance, and therefore, regulations need to be revised to include additional factors to ensure proper acoustic performance.

Multi-Zone Infection Risk Assessment Model of Airborne Virus Transmission on a Cruise Ship Using CONTAM

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.

Airborne virus transmission: Increased spreading due to formation of hollow particles

The globally supported social distancing rules to prevent airborne transmission of COVID-19 assume small saliva droplets evaporate fast and large ones, which contain most viral copies, fall fast to the ground. However, during evaporation, solutes distribute non-uniformly within the droplets. We developed a numerical model to predict saliva droplet drying in different environments. We represent saliva droplets as a solution of NaCl mixed with water. In a hot and dry ambiance, the solutes form a shell on the droplets' surface, producing light, hollow particles. These hollow particles have a larger cross-sectional area compared to their solid counterparts and can float longer and travel farther in the air. We introduced the “hollowness factor,” which serves as a measure of the ratio of the volume of a hollow particle and the volume of a solid residue formed during droplet drying. Through our investigations, we determined that under specific conditions, namely an ambient humidity level of 10% and a temperature of 40°C, the highest hollowness factor observed was 1.610. This finding indicates that in the case of hollow particle formation, the droplet nucleus expands by a factor of 1.610 compared to its original size.

Hunting for a viral proxy in bioaerosols of swine buildings using molecular detection and metagenomics

There are limited biosecurity measures directed at preventing airborne transmission of viruses in swine. The effectiveness of dust mitigation strategies such as oil sprinkling, to decrease risk of airborne virus transmission are unknown. Metagenomics and qPCR for common fecal viruses were used to hunt for a ubiquitous virus to serve as a proxy when evaluating the efficiency of mitigation strategies against airborne viral infectious agents. Air particles were collected from swine buildings using high-volume air samplers. Extracted DNA and RNA were used to perform specific RT-qPCR and qPCR and analyzed by high-throughput sequencing. Porcine astroviruses group 2 were common (from 102 to 105 genomic copies per cubic meter of air or gc/m3, 93% positivity) while no norovirus genogroup II was recovered from air samples. Porcine torque teno sus virus were detected by qPCR in low concentrations (from 101 to 102 gc/m3, 47% positivity). Among the identified viral families by metagenomics analysis, Herelleviridae, Microviridae, Myoviridae, Podoviridae, and Siphoviridae were dominant. The phage vB_AviM_AVP of Aerococcus was present in all air samples and a newly designed qPCR revealed between 101 and 105 gc/m3 among the samples taken for the present study (97% positivity) and banked samples from 5- and 15-year old studies (89% positivity). According to the present study, both the porcine astrovirus group 2 and the phage vB_AviM_AVP of Aerococcus could be proxy for airborne viruses of swine buildings.

Camera-based occupant behavior trajectory capture and on-site assessment of spatio-temporal transmission risk of airborne virus in a university office building

Aerosol transmission is a route of contagion. The engineering field predicts risk in indoor environment by simulating the airborne transmission of the virus. However, occupant behavior is one of the main causes for the gap between predicted and actual airborne virus transmission risk. To improve the accuracy of transmission risk assessment, this study presents a framework for real-time assessment of infection risk based on the behavioral trajectory of the occupants captured by cameras. The study focused on analyzing the impact of short-range exposure and long-range exposure of occupants on the infection risk through fine-grained trajectories. On-site measurements were conducted in a university office building to obtain the air change rates (ACH) and occupant contact time respectively. A numerical model for quantifying the exposure risk of the two contact routes was also developed. The results demonstrated that the individual movement is diverse. The infection risk varies with the occupied space, behavioral patterns, and exposure time. The main passages and seats in the room, corridor corners, and room doorways are areas of the high frequency of short-range contact. The fraction of long-range exposure is 57.2%, indicating long-range exposure is the dominant route for the limited scenarios and population in this study. The cumulative risk of infection was 0.021 for teachers; 0.029 for employees; and 0.045 for students, with assumptions of initial infection rates of 5%. It can provide real-time warning for occupants through on-site monitoring and contribute to the transmission control and source tracing of airborne viruses.

The effect of natural ventilation on airborne transmission of the COVID-19 virus spread by sneezing in the classroom

Since school classrooms are of vital importance due to their impact on public health in COVID-19 and similar epidemics, it is imperative to develop new ventilation strategies to reduce the risk of transmission of the virus in the classroom. To be able to develop new ventilation strategies, the effect of local flow behaviors in the classroom on the airborne transmission of the virus under the most dramatic conditions must first be determined. In this study, the effect of natural ventilation on the airborne transmission of COVID-19-like viruses in the classroom in the case of sneezing by two infected students in a reference secondary school classroom was investigated in five scenarios. Firstly, experimental measurements were carried out in the reference class to validate the computational fluid dynamics (CFD) simulation results and determine the boundary conditions. Next, the effects of local flow behaviors on the airborne transmission of the virus were evaluated for five scenarios using the Eulerian-Lagrange method, a discrete phase model, and a temporary three-dimensional CFD model. In all scenarios, immediately after sneezing, between 57 and 60.2 % of the droplets containing the virus, mostly large and medium-sized (150 μm < d < 1000 μm) settled on the infected student's desk, while small droplets continued to move in the flow field. In addition, it was determined that the effect of natural ventilation in the classroom on the travel of virus droplets in the case of Redh < 8.04 × 104 (Reynolds number, Redh=Udh/νu, dh and are fluid velocity, hydraulic diameters of the door and window sections of the class and kinematic viscosity, respectively) was negligible.

SARS-CoV-2 Inactivation in Aerosol by Means of Radiated Microwaves.

Coronaviruses are a family of viruses that cause disease in mammals and birds. In humans, coronaviruses cause infections on the respiratory tract that can be fatal. These viruses can cause both mild illnesses such as the common cold and lethal illnesses such as SARS, MERS, and COVID-19. Air transmission represents the principal mode by which people become infected by SARS-CoV-2. To reduce the risks of air transmission of this powerful pathogen, we devised a method of inactivation based on the propagation of electromagnetic waves in the area to be sanitized. We optimized the conditions in a controlled laboratory environment mimicking a natural airborne virus transmission and consistently achieved a 90% (tenfold) reduction of infectivity after a short treatment using a Radio Frequency (RF) wave emission with a power level that is safe for people according to most regulatory agencies, including those in Europe, USA, and Japan. To the best of our knowledge, this is the first time that SARS-CoV-2 has been shown to be inactivated through RF wave emission under conditions compatible with the presence of human beings and animals. Additional in-depth studies are warranted to extend the results to other viruses and to explore the potential implementation of this technology in different environmental conditions.