ABSTRACT
In light of the COVID-19 pandemic, getting infected through the built environment is being studied. The measures that should be taken to reduce infection through the built environment are essential;not only for COVID-19, but this idea is present at all times of widespread diseases.The purpose of this research is to systematically review the relationship between the built environment and the spread of infection to create a potential guideline to reduce the transmission rate. Articles and studies on the relationship between infectious disease and the built environment were reviewed.Articles matching the selection criteria were identified. Most articles described peer reviews, consensus statements, and reports. The articles have provided data that can be used as guidance for reducing the transmission of infection within the built environment. It was found that evidence has been created such as ventilation, buffer spaces, flooring, and surfaces that can reduce the infection of COVID-19.
ABSTRACT
Real-time detection of airborne infection agents present in human breath and environmental airways, such as the human respiratory Coronavirus, is important for public health. For this, a model label-free immunosensor, based on multi-walled nanotubes (MWNT)-based screen-printed graphite electrodes (SPEs), was proposed and studied. For sensing applications, MWNTs have many advantages such as small size with larger surface area, excellent electron transfer promoting ability when used for antibody immobilization, with retention of its selectivity for potential immunosensors development. In order to verify the selectivity of the selected primary antibody (anti-CoV 229E antibody) and the effective immunocomplex formation (antigen-antibody), an in-depth voltammetric characterization of MWNT-SPEs interface was carried out during the multistep fabrication of CoV immunosensor using [Fe(CN)6]3−/4− as an electroactive probe.After that, the analytical robustness of the performances of these immunosensing platforms was estimated and verified. Indeed, a nanomolar range detection limit (180 TCID50/mL)g/mL) with excellent reproducibility (RSD% = 8%) was obtained. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023.
ABSTRACT
van Veelen, Michiel J., Giulia Roveri, Ivo B. Regli, Tomas Dal Cappello, Anna Vögele, Michela Masè, Marika Falla, and Giacomo Strapazzon. Personal protective equipment protocols lead to a delayed initiation of patient assessment in mountain rescue operations. High Alt Med Biol. 24:127-131, 2023. Introduction: Mountain rescue operations can be challenging in austere environmental conditions and remote settings. Airborne infection prevention measures include donning of personal protective equipment (PPE), potentially delaying the approach to a patient. We aimed to investigate the time delay caused by these prevention measures. Methods: This randomized crossover trial consisted of 24 rescue simulation trials intended to be as realistic as possible, performed by mountain rescue teams in difficult terrain. We analyzed the time needed to perform an airborne infection prevention protocol during the approach to a patient. Time delays in scenarios involving patients already wearing versus not wearing face masks and gloves were compared using a linear mixed model Results: The airborne infection prevention measures (i.e., screening questionnaire, hand antisepsis, and donning of PPE) resulted in a time delay of 98 ± 48 (26-214) seconds on initiation of patient assessment. There was a trend to a shorter time to perform infection prevention measures if the simulated patient was already wearing PPE consisting of face mask and gloves (p = 0.052). Conclusion: Airborne infection prevention measures may delay initiation of patient assessment in mountain rescue operations and could impair clinical outcomes in time-sensitive conditions. Trial registration number 0105095-BZ Ethics Committee review board of Bolzano.
Subject(s)
Health Personnel , Rescue Work , Humans , Masks , Pandemics/prevention & control , Personal Protective Equipment , Cross-Over StudiesABSTRACT
This is an account that should be heard of an important struggle: the struggle of a large group of experts who came together at the beginning of the COVID-19 pandemic to warn the world about the risk of airborne transmission and the consequences of ignoring it. We alerted the World Health Organization about the potential significance of the airborne transmission of SARS-CoV-2 and the urgent need to control it, but our concerns were dismissed. Here we describe how this happened and the consequences. We hope that by reporting this story we can raise awareness of the importance of interdisciplinary collaboration and the need to be open to new evidence, and to prevent it from happening again. Acknowledgement of an issue, and the emergence of new evidence related to it, is the first necessary step towards finding effective mitigation solutions.
Subject(s)
COVID-19 , Humans , SARS-CoV-2 , Pandemics/prevention & control , World Health Organization , SocietiesABSTRACT
Ventilation performance plays a significant role in distributing contaminants and airborne infections indoors. Thus, poorly ventilated public spaces may be at high risk due to the presence of both infectious and susceptible people. Adapting HVAC ventilation systems to mitigate virus transmission requires considering ventilation rate, airflow patterns, air balancing, occupancy, and feature placement. The study aims to identify poorly ventilated spaces where airborne transmission of pathogens such as SARS-CoV-2 could be critical. This study is focused on evaluating the ventilation performance of the building stock and the safety of using the facilities based on measured indoor CO2. The results revealed the spaces with the potential risk of indoor airborne transmission of COVID-19. The study proposes recommendations for utilising air ventilation systems in different use cases. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.
ABSTRACT
The validity of using CO2 as an indicator of airborne infection probability was studied. Tracer gas measurements were conducted in a field lab with two breathing thermal manikins resembling "infected” and "susceptible” persons seated at desks. The room was ventilated with a mixing air distribution. Experiments were performed at three ventilation rates. CO2 gas was dosed into the air exhaled by the manikins to simulate the metabolic CO2 generation by people. Simultaneously, nitrous oxide (N2O) tracer gas was dosed into the air exhaled by one of the manikins ("infected person”) to simulate the emission of exhaled infectious particles. CO2 and N2O concentrations were measured at several points. The probability of infection was calculated based on the concentration of CO2 and N2O measured in the air inhaled by the exposed manikin ("susceptible person”). The results did not confirm that CO2 can be used as a proxy to assess the infection probability. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.
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A widely used analytical model to quantitatively assess airborne infection risk is the Wells-Riley model based on the assumption of complete air mixing in a single zone. This study aimed to extend the Wells-Riley model so that the infection risk can be calculated in spaces where complete mixing is not present. This is done by evaluating the time-dependent distribution of infectious quanta in each zone and by solving the coupled system of differential equations based on the zonal quanta concentrations. In conclusion, this study shows that using the Wells-Riley model based on the assumption of completely mixing air may overestimate the long-range airborne infection risk compared to some high-efficiency ventilation systems such as displacement ventilation, but also underestimate the infection risk in a room heated with warm air supplied from the ceiling. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.
ABSTRACT
The coronavirus disease may spread by airborne aerosols, especially in a poorly ventilated enclosure. Natural ventilation can reduce the transmission of infection. The WHO suggested the minimum ventilation rate of 10 L/s/person in non-residential settings. The objective was to evaluate risk of airborne infection with different settings in natural ventilated classroom. The risk was evaluated by using the modified Wells-Riley equation associated with the variation of contaminant concentration simulated by a multi-zone airflow model. The results provide the guidance of natural ventilation strategy in the classroom to reduce the transmission of airborne infection disease. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.
ABSTRACT
The current COVID-19 pandemic has highlighted the importance of health safety assessment in various indoor scenarios. Computational fluid dynamics (CFD) combined with a modified Wells-Riley equation provides a powerful tool to analyse local infection probability in an indoor space. Compared to a single infection probability characterising the space in the traditional Wells-Riley model, the coupled approach provides a distribution of infection probability within the space. Furthermore, this approach avoids assuming a well-mixed state, usually related to Wells-Riley equation. This study compares displacement and mixing ventilation strategies with four different ventilation rates to assess the local quanta concentrations modelled using passive scalar transport approach. The simulation results are processed to also account for the effect of wearing masks and vaccinations. The result show that a well-designed displacement ventilation system can significantly reduce infection probability compared to mixing ventilation system at similar airflow rate. Additionally, the results emphasised the importance of wearing mask and getting vaccinated as a means of reducing infection probability. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.
ABSTRACT
Risk calculators have been utilised to predict the risk of infection from SARS-CoV-2. Inputs include the dimensions of the indoor space, number of infected persons and activity, and inhalation rate of susceptible persons. The compartment model requires an estimate of the Air Changes per Hour (ACH) in the space, as the concentration is changing as a result of the dynamic balance between the generation and removal of exhaled quanta. ACH can be estimated using CO2, engineering drawings, or airflow measurements, but these estimates are often incorrect due to mechanical anomalies and mixing inefficiencies, or in the case of CO2, an absence of continuous occupancy for a sufficient amount of time. SF6 as a tracer gas to establish ACH has been used extensively for many decades to measure air exchange. This approach was utilised to assist a school in managing risk of infection in their facility during an exam period. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.
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This study investigates the effectiveness of an upper-room UVGI system in a small classroom. Mixing ventilation can increase virus removal when combined with a UVGI system more effectively than displacement ventilation combined with a UVGI system, especially in cases where the ventilation rate is low. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.
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It has been suggested that COVID-19 causes airborne infection by fine particles called droplet nuclei and reducing the risk of indoor infection by ventilation is attracting attention as an infection control measure. However, the characteristics of fine particles are not considered in indoor ventilation plans, and the behavior and removal effect of particles by ventilation have not been sufficiently clarified. Therefore, in this study, numerical analysis using a single aperture model is performed under various conditions to evaluate how indoor concentration trends and ventilation rates are affected by these factors in order to properly evaluate the outflow characteristics of chemical species and particulate matter due to ventilation. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.
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With the global outbreak of infectious respiratory diseases COVID-19, it is critical to evaluate the indoor airborne infection risk. The ventilation strategies and air distribution methods may affect indoor cross-infection significantly. This study aims to evaluate the effect of 4-way active chilled beam ventilation system on airborne infection risk. An experimental study has been conducted in a test chamber to investigate airborne transmission in an office room with two different heat load conditions and two chilled beam types. Tracer gas technique was used to simulate the exhaled droplet nuclei from the infected person and the photoacoustic gas analyser (Gasera One) was used to monitor the concentration of SF6. The revised Wells-Riley model was used to calculate the infection probability with both spatial and temporal resolutions. One of the occupants was an infector, and the influence of three factors were explored, including the infector's location, air distribution patterns, and heat load levels. To evaluate the dynamics of airborne exposure, real-time and average exposure indices were proposed. The experimental results illustrated that the airborne infection risk increased linearly within 30 min of the exposure time, and then keep a constant state. Under the same heat load conditions, 2 pcs of 1200 chilled beam system directed the particles in the occupied zone to the outlet effectively and reduced the infection rate of personnel in occupied zone. The location of the infector had a significant impact on the infection probability for the active chilled beam ventilation system. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.
ABSTRACT
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.
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We draw the attention of readers and governments to the death rate from coronavirus disease 2019 in Japan, continuing as a fraction of that experienced by many other developed nations. We think this is due to the activity of the powerful, protective lactoperoxidase system (LPO) which prevents serious airborne infections. The LPO system requires iodine, which is liberally provided by the typical Japanese diet but lacking in many others. One might consider the Japanese experience an incredibly large, open-label study exhibiting the preventative power of a high-iodine diet. We predict this favourable trend will continue for Japan because deadly variants of the severe, acute respiratory syndrome coronavirus 2 will be with us, forever.Copyright © 2023 The Scandinavian Foundation for Immunology.
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The Air borne transmission is a very big concern for highly infectious diseases like Covid-19 and other airborne diseases. A micro droplet and aerosol can be carried out in the air and can remain flowing in air over a distance in a confined space, leading to affecting high number of people getting prone to infection and it is very dangerous in enclosed spaces or shared spaces. Public places, shared facilities are the areas, where infectious aerosol can be present in the air for a long duration. Ventilation of closed spaces, shared spaces is the need of hour to have analysed and deep study in context of infectious airborne diseases. Introduction of fresh air into the enclosed environment at regular interval of times may lead to fast dilution of air present in the enclosed space. The prominent building codes and HVAC guidelines allows as to calculate ACPH (Air changes per hour) in an enclosed space as per the occupancy and flow rate. The age of air is the criteria to define the amount of air residing in the enclosed space when it enters the space till its exhaust from that space. The more the age of air in the particular area the more can be the infection probability among the occupants. It is predominant to study the airflow pattern caused due to ventilation which can be collaborated with age of air to know about the infection probability. Typically, a classroom geometry is assumed with inlet outlet boundary conditions where exhaust fan is playing a major role of displacement ventilation. Study of air recirculation zones and dead zones is the point of interest of this study. Computational fluid dynamics is the most powerful tool in the present era to study the air flow pattern in enclosed and shared spaces.Copyright © 2022, Anka Publishers. All rights reserved.
ABSTRACT
Airborne transmission via aerosol particles without close human contact is a possible source of infection with airborne viruses such as SARS-CoV-2 or influenza. Reducing this indirect infection risk, which is mostly present indoors, requires wearing adequate respiratory masks, the inactivation of the viruses with radiation or electric charges, filtering of the room air, or supplying ambient air by means of ventilation systems or open windows. For rooms without heating, ventilation, and air conditioning (HVAC) systems, mobile air cleaners are a possibility for filtering out aerosol particles and therefore lowering the probability of indirect infections. The main questions are as follows: (1) How effectively do mobile air cleaners filter the air in a room? (2) What are the parameters that influence this efficiency? (3) Are there room situations that completely prevent the air cleaner from filtering the air? (4) Does the air cleaner flow make the stay in the room uncomfortable? To answer these questions, particle imaging methods were employed. Particle image velocimetry (PIV) was used to determine the flow field in the proximity of the air cleaner inlet and outlet to assess regions of unpleasant air movements. The filtering efficiency was quantified by means of particle image counting as a measure for the particle concentration at multiple locations in the room simultaneously. Moreover, different room occupancies and room geometries were investigated. Our results confirm that mobile air cleaners are suitable devices for reducing the viral load indoors. Elongated room geometries, e.g., hallways, lead to a reduced filtering efficiency, which needs to be compensated by increasing the volume flow rate of the device or by deploying multiple smaller devices. As compared to an empty room, a room occupied with desks, desk separation walls, and people does not change the filtering efficiency significantly, i.e., the change was less than 10%. Finally, the flow induced by the investigated mobile air cleaner does not reach uncomfortable levels, as by defined room comfort standards under these conditions, while at the same time reaching air exchange rates above 6, a value which is recommended for potentially infectious environments.
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Ultraviolet Germicidal Irradiance (UVGI) is the effective technique of inactivating disease-causing bacteria, mould spores, fungi, and viruses using ultraviolet radiation. In this study, we seek to quantify the efficacy and COVID-19 infection risk reduction achieved by UVGI in the upper unoccupied zone of a room so that we may specify the type and placement of UVGI emitters optimally. We present a computational fluid dynamics (CFD) based approach to model disinfection of aerosolized pathogens in a non-uniform ultraviolet field with mixing driven by air exchange and temperature gradients. We validate our CFD against simple calculation methods for UVGI effectiveness in well mixed spaces, and we integrate it with the Wells-Riley model of airborne infection risk to assess the relative benefit of UVGI with and against other measures. We demonstrate an order of magnitude reduction in infection risk as a result of applying UVGI, as well as the ability to quantify infection risk in non-well-mixed settings where simplified calculations methods do not apply. © International Building Performance Simulation Association, 2022
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Against the background of the global spread of the new SARS-CoV-2 coronavirus, the prevention of infections with airborne mechanisms of transmission has become a priority in the Armed Forces. The development of effective COVID-19 prevention measures requires consideration of the peculiarities of military service and everyday life due to the inability of organized military collectives to comply with the requirements of the lockdown regime introduced at the peak of morbidity by the civilian health system. The patterns of incidence of COVID-19 in military personnel of the Western Military District in organized military collectives were studied in relation to the conditions of training and combat activities and the characteristics of military service. It was found that the dynamics of the incidence of COVID-19 among military personnel of the Western Military District in 2020-2021 exhibited a wave-like character and included four epidemic rises that coincided with epidemic waves among the civilian population. At the same time, from April to December 2020, the morbidity rate in military personnel was significantly higher than that in the general population, and from January to December 2021 against the background of mass vaccination of military personnel against COVID-19, the incidence rate in military personnel decreased by 50% relative to that in the general population. The effectiveness of anti-epidemic measures has increased significantly in recent months. The average number of patients in the epidemic outbreak decreased by 46.3%, the average duration of the outbreak decreased by 12.4%, and the proportion of group morbidity in the structure of the overall incidence of COVID-19 decreased by 19.8%. It is shown that the incidence of COVID-19 in various types of military collectives depends on the conditions of military service and the specifics of daily activities. The highest epidemiological significance of COVID-19 was detected in military units of constant readiness, as well as in medical and military educational organizations.
ABSTRACT
Despite the gradual return to pre-pandemic conditions, the spreading of COVID-19 (SARS-CoV-2) left several open issues. Nowadays it is know that airborne infections, including COVID-19, are conveyed by particles having the size of >5 mum (droplets) and <5 mum (droplets nuclei), ejected by coughing and sneezing [1]. While droplets undergo to dehydration and precipitation, droplet nuclei persist in air for long time after their ejection, contributing to infection spreading. Actual prevention strategies are based on non-pharmaceutical interventions act to reduce droplets diffusion and spacing from Personal Protective Equipment, such as facial masks, and social distancing measure. Nevertheless, for the new endemic phase of COVID-19 the development of new strategies for airborne infections' containment becomes unavoidable. In this project, we propose a new device for the suppression of Airborne Viral Aerosols designed to work in situations with constrained geometries (e.g. public transportation, offices, waiting rooms etc.) not allowing social distancing. The device, devised to perform photokilling of viral aerosols in air in presence of humans, has its core in an UV illumination system operating at 222 nm. It is know from literature that UV radiation alters the genetic material of viruses and bacteria whose maximum absorption wavelengths are in the far-UV range (UVC, 100-280 nm), the most effective for sterilization [2]. Differently from the operative wavelength of most commercial systems (254 nm), the higher tissue absorption prevents the 222 nm radiation to travel over the very first epidermal layers [3] constituting a minor health risk for applications in presence of people. The device combines the UV illumination system with a vertical flux of air that conveys exhaled particles to the light source and controls humidity and temperature, crucial parameters for virus diffusion. After its development, the device prototype will be tested in model experiments. Initially, its safety will be verified by monitoring in particular the UVC-induced ozone production. Then, in vitro photokilling experiments will be performed in two steps: (i) on a layer of immobilized SARS-Cov-2 virus act to obtain optimal UV doses for an effective sterilization;(ii) on SARS-Cov-2 aerosol models. For this last experiment, a model viral aerosol miming the characteristics of cough and sneeze particles will be preliminary studied and supported by synthetic data to characterize the optical properties of the reference scenario. The resulting information will be crucial for the final design of the device itself. As a last step, we will test the device in in vivo experiments. An air flux, harvesting exhaled air by infected mice, will be illuminated by the device and will be sent to healthy mice. Finally, the infectiveness of exhaled air after the UV treatment will be evaluated, providing more information for further applications in the presence of humans.Copyright © 2023