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Berlanga FA, Gomez P, Esteban A, Liu L, Nielsen PV. Three dimensional analysis of the exhalation flow in the proximity of the mouth. Heliyon 2024; 10:e26283. [PMID: 38434078 PMCID: PMC10906307 DOI: 10.1016/j.heliyon.2024.e26283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 02/02/2024] [Accepted: 02/09/2024] [Indexed: 03/05/2024] Open
Abstract
The human exhalation flow is characterized in this work from the three-dimensional velocimetry results obtained by using the stereo particle image velocimetry (SPIV) measurement technique on the flow emitted from a realistic airway model. For this purpose, the transient exhalation flow through the mouth of a person performing two different breaths corresponding to two metabolic rates, standing relaxed (SR) and walking active (WA), is emulated and studied. To reproduce the flow realistically, a detailed three-dimensional model obtained from computed tomography measurements on real subjects is used. To cope with the variability of the experimental data, a subsequent analysis of the results is performed using the TR-PIV (time resolved particle image velocimetry) technique. Exhalation produces a transient jet that becomes a puff when flow emission ends. Three-dimensional vector fields of the jet velocity are obtained in five equally spaced transverse planes up to a distance of Image 1 from the mouth at equally spaced time instants Image 2 which will be referred to as phases (φ), from the beginning to the end of exhalation. The time evolution during exhalation of the jet area of influence, the velocity field and the jet air entrainment have been characterized for each of the jet cross sections. The importance of the use of realistic airway models for the study of this type of flow and the influence of the metabolic rate on its development are also analyzed. The results obtained contribute to the characterization of the human exhalation as a pathway of the transmission of pathogens such as SARS-CoV-2 virus.
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Affiliation(s)
- F A Berlanga
- Dept. de Mecánica, ETSII, Universidad Nacional de Educación a Distancia (UNED), E-28040, Madrid, Spain
| | - P Gomez
- Dept. de Mecánica, ETSII, Universidad Nacional de Educación a Distancia (UNED), E-28040, Madrid, Spain
| | - A Esteban
- Dept. de Mecánica, ETSII, Universidad Nacional de Educación a Distancia (UNED), E-28040, Madrid, Spain
| | - L Liu
- Dept. of Building Science and Technology, School of Architecture, Tsinghua University, Haidian District, Beijing, China
| | - P V Nielsen
- Dept. of the Built Environment, Aalborg Universitet, Thomas Manns Vej 23 9220 Aalborg Øst, Denmark
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Svenson O, Isohanni F, Salo I, Lindholm T. Airborne SARS-CoV2 virus exposure, interpersonal distance, face mask and perceived risk of infection. Sci Rep 2024; 14:2285. [PMID: 38280918 PMCID: PMC10821858 DOI: 10.1038/s41598-024-52711-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2022] [Accepted: 01/23/2024] [Indexed: 01/29/2024] Open
Abstract
Participants judged the risk of an infection during a face to face conversation at different interpersonal distances from a SARS-CoV-2 infected person who wore a face mask or not, and in the same questionnaire answered questions about Corona related issues. Keeping a distance to an infected person serves as a protective measure against an infection. When an infected person moves closer, risk of infection increases. Participants were aware of this fact, but underestimated the rate at which the risk of infection increases when getting closer to an infected person, e.g., from 1.5 to 0.5 m (perceived risk increase = 3.33 times higher, objective = 9.00 times higher). This is alarming because it means that people can take risks of infection that they are not aware of or want to take, when they approach another possibly virus infected person. Correspondingly, when an infected person moves away the speed of risk decrease was underestimated, meaning that people are not aware of how much safer they will be if they move away from an infected person. The perceived risk reducing effects of a face mask were approximately correct. Judgments of infection risk at different interpersonal distances (with or without a mask) were unrelated to how often a person used a mask, avoided others or canceled meetings during the COVID-19 pandemic. Greater worry in general and in particular over COVID-19, correlated positively with more protective behavior during the pandemic, but not with judgments of infection risk at different interpersonal distances. Participants with higher scores on a cognitive numeracy test judged mask efficiency more correctly, and women were more worried and risk avoiding than men. The results have implications for understanding behavior in a pandemic, and are relevant for risk communications about the steep increase in risk when approaching a person who may be infected with an airborne virus.
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Affiliation(s)
- Ola Svenson
- Department of Psychology, Stockholm University, Stockholm, Sweden.
- Decision Research, Eugene, OR, USA.
| | - Freja Isohanni
- Department of Psychology, Stockholm University, Stockholm, Sweden
| | - Ilkka Salo
- Department of Psychology, Lund University, Lund, Sweden
| | - Torun Lindholm
- Department of Psychology, Stockholm University, Stockholm, Sweden
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Voidarou C, Rozos G, Stavropoulou E, Giorgi E, Stefanis C, Vakadaris G, Vaou N, Tsigalou C, Kourkoutas Y, Bezirtzoglou E. COVID-19 on the spectrum: a scoping review of hygienic standards. Front Public Health 2023; 11:1202216. [PMID: 38026326 PMCID: PMC10646607 DOI: 10.3389/fpubh.2023.1202216] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Accepted: 10/16/2023] [Indexed: 12/01/2023] Open
Abstract
The emergence of COVID-19 in Wuhan, China, rapidly escalated into a worldwide public health crisis. Despite numerous clinical treatment endeavors, initial defenses against the virus primarily relied on hygiene practices like mask-wearing, meticulous hand hygiene (using soap or antiseptic solutions), and maintaining social distancing. Even with the subsequent advent of vaccines and the commencement of mass vaccination campaigns, these hygiene measures persistently remain in effect, aiming to curb virus transmission until the achievement of herd immunity. In this scoping review, we delve into the effectiveness of these measures and the diverse transmission pathways, focusing on the intricate interplay within the food network. Furthermore, we explore the virus's pathophysiology, considering its survival on droplets of varying sizes, each endowed with distinct aerodynamic attributes that influence disease dispersion dynamics. While respiratory transmission remains the predominant route, the potential for oral-fecal transmission should not be disregarded, given the protracted presence of viral RNA in patients' feces after the infection period. Addressing concerns about food as a potential viral vector, uncertainties shroud the virus's survivability and potential to contaminate consumers indirectly. Hence, a meticulous and comprehensive hygienic strategy remains paramount in our collective efforts to combat this pandemic.
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Affiliation(s)
| | - Georgios Rozos
- Veterinary Directorate, South Aegean Region, Ermoupolis, Greece
| | - Elisavet Stavropoulou
- Department of Medicine, Lausanne University Hospital (CHUV), University of Lausanne, Lausanne, Switzerland
| | - Elpida Giorgi
- Laboratory of Hygiene and Environmental Protection, Department of Medicine, Democritus University of Thrace, Alexandroupolis, Greece
| | - Christos Stefanis
- Laboratory of Hygiene and Environmental Protection, Department of Medicine, Democritus University of Thrace, Alexandroupolis, Greece
| | - Georgios Vakadaris
- Laboratory of Hygiene and Environmental Protection, Department of Medicine, Democritus University of Thrace, Alexandroupolis, Greece
| | - Natalia Vaou
- Laboratory of Hygiene and Environmental Protection, Department of Medicine, Democritus University of Thrace, Alexandroupolis, Greece
| | - Christina Tsigalou
- Laboratory of Hygiene and Environmental Protection, Medical School, Democritus University of Thrace, Alexandroupolis, Greece
| | - Yiannis Kourkoutas
- Laboratory of Applied Microbiology and Biotechnology, Department of Molecular Biology and Genetics, Democritus University of Thrace, Alexandroupolis, Greece
| | - Eugenia Bezirtzoglou
- Laboratory of Hygiene and Environmental Protection, Department of Medicine, Democritus University of Thrace, Alexandroupolis, Greece
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4
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Caracci E, Stabile L, Ferro AR, Morawska L, Buonanno G. Respiratory particle emission rates from children during speaking. Sci Rep 2023; 13:18294. [PMID: 37880507 PMCID: PMC10600129 DOI: 10.1038/s41598-023-45615-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Accepted: 10/21/2023] [Indexed: 10/27/2023] Open
Abstract
The number of respiratory particles emitted during different respiratory activities is one of the main parameters affecting the airborne transmission of respiratory pathogens. Information on respiratory particle emission rates is mostly available for adults (few studies have investigated adolescents and children) and generally involves a limited number of subjects. In the present paper we attempted to reduce this knowledge gap by conducting an extensive experimental campaign to measure the emission of respiratory particles of more than 400 children aged 6 to 12 years while they pronounced a phonetically balanced word list at two different voice intensity levels ("speaking" and "loudly speaking"). Respiratory particle concentrations, particle distributions, and exhaled air flow rates were measured to estimate the respiratory particle emission rate. Sound pressure levels were also simultaneously measured. We found out that median respiratory particle emission rates for speaking and loudly speaking were 26 particles s-1 (range 7.1-93 particles s-1) and 41 particles s-1 (range 10-146 particles s-1), respectively. Children sex was significant for emission rates, with higher emission rates for males during both speaking and loudly speaking. No effect of age on the emission rates was identified. Concerning particle size distributions, for both respiratory activities, a main mode at approximately 0.6 µm and a second minor mode at < 2 µm were observed, and no differences were found between males and females. This information provides important input parameters in predictive models adopted to estimate the transmission risk of airborne pathogens in indoor spaces.
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Affiliation(s)
- Elisa Caracci
- Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Cassino, FR, Italy
| | - Luca Stabile
- Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Cassino, FR, Italy.
| | - Andrea R Ferro
- Department of Civil and Environmental Engineering, Clarkson University, Potsdam, NY, USA
| | - Lidia Morawska
- International Laboratory for Air Quality and Health, Queensland University of Technology, Brisbane, QLD, Australia
| | - Giorgio Buonanno
- Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Cassino, FR, Italy
- International Laboratory for Air Quality and Health, Queensland University of Technology, Brisbane, QLD, Australia
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A review on indoor airborne transmission of COVID-19– modelling and mitigation approaches. JOURNAL OF BUILDING ENGINEERING 2023; 64:105599. [PMCID: PMC9699823 DOI: 10.1016/j.jobe.2022.105599] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 11/11/2022] [Accepted: 11/21/2022] [Indexed: 06/09/2023]
Abstract
In the past few years, significant efforts have been made to investigate the transmission of COVID-19. This paper provides a review of the COVID-19 airborne transmission modeling and mitigation strategies. The simulation models here are classified into airborne transmission infectious risk models and numerical approaches for spatiotemporal airborne transmissions. Mathematical descriptions and assumptions on which these models have been based are discussed. Input data used in previous simulation studies to assess the dispersion of COVID-19 are extracted and reported. Moreover, measurements performed to study the COVID-19 airborne transmission within indoor environments are introduced to support validations for anticipated future modeling studies. Transmission mitigation strategies recommended in recent studies have been classified to include modifying occupancy and ventilation operations, using filters and air purifiers, installing ultraviolet (UV) air disinfection systems, and personal protection compliance, such as wearing masks and social distancing. The application of mitigation strategies to various building types, such as educational, office, public, residential, and hospital, is reviewed. Recommendations for future works are also discussed based on the current apparent knowledge gaps covering both modeling and mitigation approaches. Our findings show that different transmission mitigation measures were recommended for various indoor environments; however, there is no conclusive work reporting their combined effects on the level of mitigation that may be achieved. Moreover, further studies should be conducted to understand better the balance between approaches to mitigating the viral transmissions in buildings and building energy consumption.
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Bahramian A. Influence of indoor environmental conditions on airborne transmission and lifetime of sneeze droplets in a confined space: a way to reduce COVID-19 spread. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2023; 30:44067-44085. [PMID: 36680724 PMCID: PMC9867553 DOI: 10.1007/s11356-023-25421-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Accepted: 01/16/2023] [Indexed: 06/17/2023]
Abstract
Effects of indoor temperature (T∞) and relative humidity (RH∞) on the airborne transmission of sneeze droplets in a confined space were studied over the T∞ range of 15-30 °C and RH∞ of 22-62%. In addition, a theoretical evaporation model was used to estimate the droplet lifetime based on experimental data. The results showed that the body mass index (BMI) of the participants played an important role in the sneezing jet velocity, while the impact of the BMI and gender of participants was insignificant on the size distribution of droplets. At a critical relative humidity RH∞,crit of 46%, the sneezing jet velocity and droplet lifetime were roughly independent of T∞. At RH∞ < RH∞,crit, the sneezing jet velocity decreased by increasing T∞ from 15 to 30 °C, while its trend was reversed at RH∞ > RH∞,crit. The maximum spreading distance of aerosols increased by decreasing the RH∞ and increasing T∞, while the droplet lifetime increased by decreasing T∞ at RH∞ > RH∞,crit. The mean diameter of aerosolized droplets was less affected by T∞ than the large droplets at RH∞ < RH∞,crit, while the mean diameter and number fraction of aerosols were more influenced by RH∞ than the T∞ in the range of 46% ≤ RH∞ ≤ 62%. In summary, this study suggests suitable indoor environmental conditions by considering the transmission rate and lifetime of respiratory droplets to reduce the spread of COVID-19.
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Affiliation(s)
- Alireza Bahramian
- Department of Chemical Engineering, Hamedan University of Technology, P.O. Box, Hamedan, 65155, Iran.
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Norvihoho LK, Yin J, Zhou ZF, Han J, Chen B, Fan LH, Lichtfouse E. Mechanisms controlling the transport and evaporation of human exhaled respiratory droplets containing the severe acute respiratory syndrome coronavirus: a review. ENVIRONMENTAL CHEMISTRY LETTERS 2023; 21:1701-1727. [PMID: 36846189 PMCID: PMC9944801 DOI: 10.1007/s10311-023-01579-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Accepted: 02/13/2023] [Indexed: 05/24/2023]
Abstract
Transmission of the coronavirus disease 2019 is still ongoing despite mass vaccination, lockdowns, and other drastic measures to control the pandemic. This is due partly to our lack of understanding on the multiphase flow mechanics that control droplet transport and viral transmission dynamics. Various models of droplet evaporation have been reported, yet there is still limited knowledge about the influence of physicochemical parameters on the transport of respiratory droplets carrying the severe acute respiratory syndrome coronavirus 2. Here we review the effects of initial droplet size, environmental conditions, virus mutation, and non-volatile components on droplet evaporation and dispersion, and on virus stability. We present experimental and computational methods to analyze droplet transport, and factors controlling transport and evaporation. Methods include thermal manikins, flow techniques, aerosol-generating techniques, nucleic acid-based assays, antibody-based assays, polymerase chain reaction, loop-mediated isothermal amplification, field-effect transistor-based assay, and discrete and gas-phase modeling. Controlling factors include environmental conditions, turbulence, ventilation, ambient temperature, relative humidity, droplet size distribution, non-volatile components, evaporation and mutation. Current results show that medium-sized droplets, e.g., 50 µm, are sensitive to relative humidity. Medium-sized droplets experience delayed evaporation at high relative humidity, and increase airborne lifetime and travel distance. By contrast, at low relative humidity, medium-sized droplets quickly shrink to droplet nuclei and follow the cough jet. Virus inactivation within a few hours generally occurs at temperatures above 40 °C, and the presence of viral particles in aerosols impedes droplet evaporation.
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Affiliation(s)
- Leslie Kojo Norvihoho
- State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an, 710049 Shaanxi People’s Republic of China
| | - Jing Yin
- State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an, 710049 Shaanxi People’s Republic of China
| | - Zhi-Fu Zhou
- State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an, 710049 Shaanxi People’s Republic of China
| | - Jie Han
- School of Human Settlements and Civil Engineering, Xi’an Jiaotong University, Xi’an, 710049 Shaanxi People’s Republic of China
| | - Bin Chen
- State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an, 710049 Shaanxi People’s Republic of China
| | - Li-Hong Fan
- The First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, 710061 Shaanxi People’s Republic of China
| | - Eric Lichtfouse
- State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an, 710049 Shaanxi People’s Republic of China
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8
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Bahramian A, Mohammadi M, Ahmadi G. Effect of indoor temperature on the velocity fields and airborne transmission of sneeze droplets: An experimental study and transient CFD modeling. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 858:159444. [PMID: 36252673 PMCID: PMC9569930 DOI: 10.1016/j.scitotenv.2022.159444] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Revised: 10/08/2022] [Accepted: 10/11/2022] [Indexed: 05/03/2023]
Abstract
The spread of the COVID-19 pandemic through the airborne transmission of coronavirus-containing droplets emitted during coughing, sneezing, and speaking has now been well recognized. This study presented the effect of indoor temperature (T∞) on the airflow dynamics, velocity fields, size distribution, and airborne transmission of sneeze droplets in a confined space through experimental investigation and computational fluid dynamic (CFD) modeling. The CFD simulations were performed using the renormalization group k-ε turbulence model. The experimental shadowgraph imaging and CFD simulations showed the time evolution of sneeze droplet concentrations into the turbulent expanded puff, droplet cloud, and fully-dispersed droplets. Also, the predicted mean velocity of droplets was compared with the obtained experimental data to assess the accuracy of the results. In addition, the validated computational model was used to study the sneeze complex airflow behavior and airborne transmission of small, medium, and large respiratory droplets in confined spaces at different temperatures. The warm room showed more than ∼14 % increase in airborne aerosols than the room with a mild temperature. The study provides information on the effect of room temperature on the evaporation of respiratory droplets during sneezing. The findings of this fundamental study may be used in developing exposure guidelines by controlling the temperature level in indoor environments to reduce the exposure risk of COVID-19.
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Affiliation(s)
- Alireza Bahramian
- Department of Chemical Engineering, Hamedan University of Technology, P.O. Box 65155, Hamedan, Iran.
| | - Maryam Mohammadi
- Department of Chemical Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran
| | - Goodarz Ahmadi
- Department of Mechanical and Aerospace Engineering, Clarkson University, Potsdam, NY 13699, USA
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Vohra SB, Kumar CM. International survey of ophthalmic anaesthesia service provision, protection of anaesthesia providers and patients during COVID-19 pandemic: a wake-up call. Eye (Lond) 2023; 37:548-553. [PMID: 35220400 PMCID: PMC8881697 DOI: 10.1038/s41433-022-01979-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Revised: 01/25/2022] [Accepted: 02/08/2022] [Indexed: 11/09/2022] Open
Abstract
AIMS This international survey was conducted to study the impact of Covid-19 pandemic on the provision and practices of ophthalmic anaesthesia, evaluate the methods employed by parent ophthalmic units for safeguarding their anaesthesia providers and patients during lockdown, and to assess pandemic's effect on anaesthesia providers as individuals. The study was done with the hope that the results will help in protecting patients and safeguarding precious human resource by better management if this pandemic was to continue or there was to be another pandemic. METHODS An anonymous questionnaire survey was distributed electronically between December 2020-January 2021 to the practicing ophthalmic anaesthesia providers in different parts of the world. RESULTS The survey identified that apart from reducing elective operating services, the ophthalmic units were ill prepared for the pandemic and the overall management was lacklustre. There was a definite lack of effective peri-operative patient screening, and, streaming processes. Measures for personal protection of staff were not optimal especially during regional/local ophthalmic anaesthesia. Severity of the pandemic, sudden job plan changes, and redeployment to intensive care units/acute covid wards had an adverse psychological impact on the affected staff. CONCLUSION Ophthalmic anaesthesia services worldwide have had poor attentiveness to the life-threatening menace and reality of Covid-19 pandemic. A review of the institutional practices to address correctible deficiencies is urgently required. Robust, mandatory, elective, timely preventative strategies need to be implemented to protect patients, and, the precious ophthalmic workforce from potential adverse physical and psychological injuries.
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Affiliation(s)
- Shashi B. Vohra
- Department of Anaesthesia, Critical Care and Pain Management, Sandwell and West Birmingham Hospitals NHS Trust, Birmingham Midland Eye Centre, City Hospital, Dudley Road, Birmingham, B18 7QH UK
| | - Chandra M. Kumar
- Newcastle University, Gelang Patah, Johor Malaysia ,grid.415203.10000 0004 0451 6370Department of Anaesthesia, Khoo Teck Puat Hospital, Yishun Central 90, Singapore, 768828 Singapore
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Argyropoulos CD, Skoulou V, Efthimiou G, Michopoulos AK. Airborne transmission of biological agents within the indoor built environment: a multidisciplinary review. AIR QUALITY, ATMOSPHERE, & HEALTH 2022; 16:477-533. [PMID: 36467894 PMCID: PMC9703444 DOI: 10.1007/s11869-022-01286-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Accepted: 11/17/2022] [Indexed: 06/17/2023]
Abstract
The nature and airborne dispersion of the underestimated biological agents, monitoring, analysis and transmission among the human occupants into building environment is a major challenge of today. Those agents play a crucial role in ensuring comfortable, healthy and risk-free conditions into indoor working and leaving spaces. It is known that ventilation systems influence strongly the transmission of indoor air pollutants, with scarce information although to have been reported for biological agents until 2019. The biological agents' source release and the trajectory of airborne transmission are both important in terms of optimising the design of the heating, ventilation and air conditioning systems of the future. In addition, modelling via computational fluid dynamics (CFD) will become a more valuable tool in foreseeing risks and tackle hazards when pollutants and biological agents released into closed spaces. Promising results on the prediction of their dispersion routes and concentration levels, as well as the selection of the appropriate ventilation strategy, provide crucial information on risk minimisation of the airborne transmission among humans. Under this context, the present multidisciplinary review considers four interrelated aspects of the dispersion of biological agents in closed spaces, (a) the nature and airborne transmission route of the examined agents, (b) the biological origin and health effects of the major microbial pathogens on the human respiratory system, (c) the role of heating, ventilation and air-conditioning systems in the airborne transmission and (d) the associated computer modelling approaches. This adopted methodology allows the discussion of the existing findings, on-going research, identification of the main research gaps and future directions from a multidisciplinary point of view which will be helpful for substantial innovations in the field.
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Affiliation(s)
| | - Vasiliki Skoulou
- B3 Challenge Group, Chemical Engineering, School of Engineering, University of Hull, Cottingham Road, Hull, HU6 7RX UK
| | - Georgios Efthimiou
- Centre for Biomedicine, Hull York Medical School, University of Hull, Cottingham Road, Hull, HU6 7RX UK
| | - Apostolos K. Michopoulos
- Energy & Environmental Design of Buildings Research Laboratory, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus
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11
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Avni O, Dagan Y. Dispersion of free-falling saliva droplets by two-dimensional vortical flows. THEORETICAL AND COMPUTATIONAL FLUID DYNAMICS 2022; 36:993-1011. [PMID: 36373071 PMCID: PMC9638496 DOI: 10.1007/s00162-022-00633-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Accepted: 10/07/2022] [Indexed: 06/16/2023]
Abstract
ABSTRACT The dispersion of respiratory saliva droplets by indoor wake structures may enhance the transmission of various infectious diseases, as the wake spreads virus-laden droplets across the room. Thus, this study analyzes the interaction between vortical wake structures and exhaled multi-component saliva droplets. A self-propelling analytically described dipolar vortex is chosen as a model wake flow, passing through a cloud of micron-sized evaporating saliva droplets. The droplets' spatial location, velocity, diameter, and temperature are traced, coupled to their local flow field. For the first time, the wake structure decay is incorporated and analyzed, which is proved essential for accurately predicting the settling distances of the dispersed droplets. The model also considers the nonvolatile saliva components, adequately capturing the essence of droplet-aerosol transition and predicting the equilibrium diameter of the residual aerosols. Our analytic model reveals non-intuitive interactions between wake flows, droplet relaxation time, gravity, and transport phenomena. We reveal that given the right conditions, a virus-laden saliva droplet might translate to distances two orders of magnitude larger than the carrier-flow characteristic size. Moreover, accounting for the nonvolatile contents inside the droplet may lead to fundamentally different dispersion and settling behavior compared to non-evaporating particles or pure water droplets. Ergo, we suggest that the implementation of more complex evaporation models might be critical in high-fidelity simulations aspiring to assess the spread of airborne respiratory droplets.
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Affiliation(s)
- Orr Avni
- Faculty of Aerospace Engineering, Technion - Israel Institute of Technology, 320003 Haifa, Israel
| | - Yuval Dagan
- Faculty of Aerospace Engineering, Technion - Israel Institute of Technology, 320003 Haifa, Israel
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12
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Mikszewski A, Stabile L, Buonanno G, Morawska L. The airborne contagiousness of respiratory viruses: A comparative analysis and implications for mitigation. GEOSCIENCE FRONTIERS 2022; 13:101285. [PMID: 38620948 PMCID: PMC8378671 DOI: 10.1016/j.gsf.2021.101285] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Revised: 07/22/2021] [Accepted: 08/06/2021] [Indexed: 05/07/2023]
Abstract
The infectious emission rate is a fundamental input parameter for airborne transmission risk assessment, but data are limited due to reliance on estimates from chance superspreading events. This study assesses the strength of a predictive estimation approach developed by the authors for SARS-CoV-2 and uses novel estimates to compare the contagiousness of respiratory pathogens. We applied the approach to SARS-CoV-1, SARS-CoV-2, MERS, measles virus, adenovirus, rhinovirus, coxsackievirus, seasonal influenza virus and Mycobacterium tuberculosis (TB) and compared quanta emission rate (ERq) estimates to literature values. We calculated infection risk in a prototypical classroom and barracks to assess the relative ability of ventilation to mitigate airborne transmission. Our median standing and speaking ERq estimate for SARS-CoV-2 (2.7 quanta h-1) is similar to active, untreated TB (3.1 quanta h-1), higher than seasonal influenza (0.17 quanta h-1), and lower than measles virus (15 quanta h-1). We calculated event reproduction numbers above 1 for SARS-CoV-2, measles virus, and untreated TB in both the classroom and barracks for an activity level of standing and speaking at low, medium and high ventilation rates of 2.3, 6.6 and 14 L per second per person (L s-1 p-1), respectively. Our predictive ERq estimates are consistent with the range of values reported over decades of research. In congregate settings, current ventilation standards are unlikely to control the spread of viruses with upper quartile ERq values above 10 quanta h-1, such as SARS-CoV-2, indicating the need for additional control measures.
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Affiliation(s)
- Alex Mikszewski
- International Laboratory for Air Quality and Health, Queensland University of Technology, Brisbane, Queensland, Australia
- CIUS Building Performance Lab, The City University of New York, New York, NY, USA
| | - Luca Stabile
- Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Cassino, FR, Italy
| | - Giorgio Buonanno
- International Laboratory for Air Quality and Health, Queensland University of Technology, Brisbane, Queensland, Australia
- Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Cassino, FR, Italy
| | - Lidia Morawska
- International Laboratory for Air Quality and Health, Queensland University of Technology, Brisbane, Queensland, Australia
- Global Centre for Clean Air Research (GCARE), Department of Civil and Environmental Engineering, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford GU2 7XH, United Kingdom
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13
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Wedel J, Steinmann P, Štrakl M, Hriberšek M, Cui Y, Ravnik J. Anatomy matters: The role of the subject-specific respiratory tract on aerosol deposition - A CFD study. COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING 2022; 401:115372. [PMID: 35919629 PMCID: PMC9333481 DOI: 10.1016/j.cma.2022.115372] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The COVID-19 pandemic is one of the greatest challenges to humanity nowadays. COVID-19 virus can replicate in the host's larynx region, which is in contrast to other viruses that replicate in lungs only, i.e. SARS. This is conjectured to support a fast spread of COVID-19. However, there is sparse research in this field about quantitative comparison of virus load in the larynx for varying susceptible individuals. In this regard the lung geometry itself could influence the risk of reproducing more pathogens and consequently exhaling more virus. Disadvantageously, there are only sparse lung geometries available. To still be able to investigate realistic geometrical deviations we employ three different digital replicas of human airways up to the 7 th level of bifurcation, representing two realistic lungs (male and female) as well as a more simplified experimental model. Our aim is to investigate the influence of breathing scenarios on aerosol deposition in anatomically different, realistic human airways. In this context, we employ three levels of cardiovascular activity as well as reported experimental particle size distributions by means of Computational Fluid Dynamics (CFD) with special focus on the larynx region to enable new insights into the local virus loads in human respiratory tracts. In addition, the influence of more realistic boundary conditions is investigated by performing transient simulations of a complete respiratory cycle in the upper lung regions of the considered respiratory models, focusing in particular on deposition in the oral cavity, the laryngeal region, and trachea, while simplifying the tracheobronchial tree. The aerosol deposition is modeled via OpenFOAM\protect \relax \special {t4ht=®} by employing an Euler-Lagrangian frame including steady and unsteady Reynolds Averaged Navier-Stokes (RANS) resolved turbulent flow using the k- ω -SST and k- ω -SST DES turbulence models. We observed that the respiratory geometry altered the local deposition patterns, especially in the laryngeal region. Despite the larynx region, the effects of varying flow rate for the airway geometries considered were found to be similar in the majority of respiratory tract regions. For all particle size distributions considered, localized particle accumulation occurred in the larynx of all considered lung models, which were more pronounced for larger particle size distributions. Moreover, it was found, that employing transient simulations instead of steady-state analysis, the overall particle deposition pattern is maintained, however with a stronger intensity in the transient cases.
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Affiliation(s)
- Jana Wedel
- Institute of Applied Mechanics, Universität Erlangen-Nürnberg, Germany
| | - Paul Steinmann
- Institute of Applied Mechanics, Universität Erlangen-Nürnberg, Germany
- Glasgow Computational Engineering Center, University of Glasgow, United Kingdom
| | - Mitja Štrakl
- Faculty of Mechanical Engineering, University of Maribor, Slovenia
| | - Matjaž Hriberšek
- Faculty of Mechanical Engineering, University of Maribor, Slovenia
| | - Yan Cui
- Huazhong University of Science and Technology, Wuhan, China
| | - Jure Ravnik
- Faculty of Mechanical Engineering, University of Maribor, Slovenia
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14
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Schmitt J, Wang J. A critical review on the role of leakages in the facemask protection against SARS-CoV-2 infection with consideration of vaccination and virus variants. INDOOR AIR 2022; 32:e13127. [PMID: 36305058 PMCID: PMC9828278 DOI: 10.1111/ina.13127] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Revised: 09/18/2022] [Accepted: 09/19/2022] [Indexed: 05/28/2023]
Abstract
The protection provided by facemasks has been extensively investigated since the beginning of the SARS-CoV-2 outbreak, focusing mostly on the filtration efficiency of filter media for filtering face pieces (FFP), surgical masks, and cloth masks. However, faceseal leakage is a major contributor to the number of potentially infectious airborne droplets entering the respiratory system of a susceptible individual. The identification of leaking spots and the quantification of leaking flows are crucial to estimate the protection provided by facemasks. This study presents a critical review on the measurement and calculation of facemask leakages and a quantitative analysis of their role in the risk of SARS-CoV-2 infection. It shows that the pairing between the mask dimensions and the wearer's face is essential to improve protection efficiency, especially for FFP2 masks, and summarizes the most common leaking spots at the interface between the mask and the wearer's face. Leakage is a crucial factor in the calculation of the protection provided by facemasks and outweighs the filtration performances. The fit factors measured among mask users were summarized for different types of face protection. The reviewed data were integrated into a computational model to compare the mitigation impact of facemasks with vaccination with consideration of new variants of SARS-CoV-2. Combining a high adoption rate of facemasks and a high vaccination rate is crucial to efficiently control the spread of highly infectious variants.
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Affiliation(s)
- Jean Schmitt
- Department of Civil, Environmental and Geomatic Engineering, ETH ZurichInstitute of Environmental EngineeringZurichSwitzerland
- Laboratory for Advanced Analytical Technologies, EmpaSwiss Federal Laboratories for Materials Science and TechnologyDubendorfSwitzerland
| | - Jing Wang
- Department of Civil, Environmental and Geomatic Engineering, ETH ZurichInstitute of Environmental EngineeringZurichSwitzerland
- Laboratory for Advanced Analytical Technologies, EmpaSwiss Federal Laboratories for Materials Science and TechnologyDubendorfSwitzerland
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15
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Reveil M, Chen YH. Predicting and preventing COVID-19 outbreaks in indoor environments: an agent-based modeling study. Sci Rep 2022; 12:16076. [PMID: 36168021 PMCID: PMC9514194 DOI: 10.1038/s41598-022-18284-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Accepted: 08/09/2022] [Indexed: 11/09/2022] Open
Abstract
How to mitigate the spread of infectious diseases like COVID-19 in indoor environments remains an important research question. In this study, we propose an agent-based modeling framework to evaluate facility usage policies that aim to lower the probability of outbreaks. The proposed framework is individual-based, spatially-resolved with time resolution of up to 1 s, and takes into detailed account specific floor layouts, occupant schedules and movement. It enables decision makers to compute realistic contact networks and generate risk profiles of their facilities without relying on wearable devices, smartphone tagging or surveillance cameras. Our demonstrative modeling results indicate that not all facility occupants present the same risk of starting an outbreak, where the driver of outbreaks varies with facility layouts as well as individual occupant schedules. Therefore, generic mitigation strategies applied across all facilities should be considered inferior to tailored policies that take into account individual characteristics of the facilities of interest. The proposed modeling framework, implemented in Python and now available to the public in an open-source platform, enables such strategy evaluation.
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16
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Morawska L, Buonanno G, Mikszewski A, Stabile L. The physics of respiratory particle generation, fate in the air, and inhalation. NATURE REVIEWS. PHYSICS 2022; 4:723-734. [PMID: 36065441 PMCID: PMC9430019 DOI: 10.1038/s42254-022-00506-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 08/03/2022] [Indexed: 05/31/2023]
Abstract
Given that breathing is one of the most fundamental physiological functions, there is an urgent need to broaden our understanding of the fluid dynamics that governs it. There would be many benefits from doing so, including a better assessment of respiratory health, a basis for more precise delivery of pharmaceutical drugs for treatment, and the understanding and potential minimization of respiratory infection transmission. We review the physics of particle generation in the respiratory tract, the fate of these particles in the air on exhalation and the physics of particle inhalation. The main focus is on evidence from experimental studies. We conclude that although there is qualitative understanding of the generation of particles in the respiratory tract, a basic quantitative knowledge of the characteristics of the particles emitted during respiratory activities and their fate after emission, and a theoretical understanding of particle deposition during inhalation, nevertheless the general understanding of the entire process is rudimentary, and many open questions remain.
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Affiliation(s)
- Lidia Morawska
- Queensland University of Technology, International Laboratory for Air Quality & Health (ILAQH), Brisbane, Queensland Australia
- Global Centre for Clean Air Research, Department of Civil and Environmental Engineering, University of Surrey, Guildford, UK
| | - Giorgio Buonanno
- Queensland University of Technology, International Laboratory for Air Quality & Health (ILAQH), Brisbane, Queensland Australia
- Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Cassino, Italy
| | - Alex Mikszewski
- Queensland University of Technology, International Laboratory for Air Quality & Health (ILAQH), Brisbane, Queensland Australia
| | - Luca Stabile
- Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Cassino, Italy
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17
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The effects of indoor temperature and humidity on local transmission of COVID-19 and how it relates to global trends. PLoS One 2022; 17:e0271760. [PMID: 35947557 PMCID: PMC9365153 DOI: 10.1371/journal.pone.0271760] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Accepted: 07/07/2022] [Indexed: 11/30/2022] Open
Abstract
During the COVID-19 pandemic, analyses on global data have not reached unanimous consensus on whether warmer and humid weather curbs the spread of the SARS-CoV-2 virus. We conjectured that this lack of consensus is due to the discrepancy between global environmental data such as temperature and humidity being collected outdoors, while most infections have been reported to occur indoors, where conditions can be different. Thus, we have methodologically investigated the effect of temperature and relative humidity on the spread of expired respiratory droplets from the mouth, which are assumed to be the main cause of most short-range infections. Calculating the trajectory of individual droplets using an experimentally validated evaporation model, the final height and distance of the evaporated droplets is obtained, and then correlated with global COVID-19 spread. Increase in indoor humidity is associated with reduction in COVID-19 spread, while temperature has no statistically significant effect.
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18
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Assessing suspension and infectivity times of virus-loaded aerosols involved in airborne transmission. Proc Natl Acad Sci U S A 2022; 119:e2204593119. [PMID: 35930663 PMCID: PMC9371747 DOI: 10.1073/pnas.2204593119] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Airborne transmission occurs through droplet-mediated transport of viruses following the expulsion of an aerosol by an infected host. Transmission efficiency results from the interplay between virus survival in the drying droplet and droplet suspension time in the air, controlled by the coupling between water evaporation and droplet sedimentation. Furthermore, droplets are made of a respiratory fluid and thus, display a complex composition consisting of water and nonvolatile solutes. Here, we quantify the impact of this complex composition on the different phenomena underlying transmission. Solutes lead to a nonideal thermodynamic behavior, which sets an equilibrium droplet size that is independent of relative humidity. In contrast, solutes do not significantly hinder transport due to their low initial concentration. Realistic suspension times are computed and increase with increasing relative humidity or decreasing temperature. By uncoupling drying and suspended stages, we observe that enveloped viruses may remain infectious for hours in dried droplets. However, their infectivity decreases with increasing relative humidity or temperature after dozens of minutes. Examining expelled droplet size distributions in the light of these results leads to distinguishing two aerosols. Most droplets measure between 0 and 40 µm and compose an aerosol that remains suspended for hours. Its transmission efficiency is controlled by infectivity, which decreases with increasing humidity and temperature. Larger droplets form an aerosol that only remains suspended for minutes but corresponds to a much larger volume and thus, viral load. Its transmission efficiency is controlled by droplet suspension time, which decreases with increasing humidity and decreasing temperature.
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19
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Park J, Lee KS, Park H. Optimized mechanism for fast removal of infectious pathogen-laden aerosols in the negative-pressure unit. JOURNAL OF HAZARDOUS MATERIALS 2022; 435:128978. [PMID: 35472540 PMCID: PMC9020843 DOI: 10.1016/j.jhazmat.2022.128978] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2022] [Revised: 04/09/2022] [Accepted: 04/18/2022] [Indexed: 05/07/2023]
Abstract
It has been frequently emphasized that highly contagious respiratory disease pathogens (such as SARS-CoV-2) are transmitted to the other hosts in the form of micro-sized aerosols (< 5 μm) in the air without physical contacts. Hospital environments such as negative-pressure unit are considered being consistently exposed to pathogens, so it is essential to quickly discharge them through the effective ventilation system. To achieve that, in the present study, we propose the optimized ventilation mechanism and design for the fastest removal of pathogen-laden aerosol using numerical simulations. We quantitatively evaluated the aerosol removal performance of various ventilation configurations (combinations of air exhaust and supply ducts), and found that the key mechanism is to form the coherent (preferentially upward) airflow structure to surround the respiratory flow containing the aerosol cluster. We believe that the present findings will play a critical role in developing the high-efficiency negative-pressure facility irrespective of its size and environments.
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Affiliation(s)
- Jooyeon Park
- Department of Mechanical Engineering, Seoul National University, Seoul 08826, South Korea
| | - Kwang Suk Lee
- Department of Urology, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul 06273, South Korea
| | - Hyungmin Park
- Department of Mechanical Engineering, Seoul National University, Seoul 08826, South Korea; Institute of Advanced Machines and Design, Seoul National University, Seoul 08826, South Korea.
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20
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Yu X, Gu H, Yin W, Sun Q, Zhou Y. Experimental research on droplets releasing characteristics of the bubble bursting behavior at a free surface with an aerosol. ANN NUCL ENERGY 2022. [DOI: 10.1016/j.anucene.2022.109109] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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21
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Lunati I, Mucignat C. Infection risk in cable cars and other enclosed spaces. INDOOR AIR 2022; 32:e13094. [PMID: 36040286 PMCID: PMC9539082 DOI: 10.1111/ina.13094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/09/2022] [Revised: 06/10/2022] [Accepted: 07/15/2022] [Indexed: 06/15/2023]
Abstract
As virus-laden aerosols can accumulate and remain suspended for hours in insufficiently ventilated enclosed spaces, indoor environments can heavily contribute to the spreading of airborne infections. In the COVID-19 pandemics, the role possibly played by cable cars has attracted media attention following several outbreaks in ski resort. To assess the real risk of infection, we experimentally characterize the natural ventilation in cable cars and develop a general stochastic model of infection in an arbitrary indoor space that accounts for the epidemiological situation, the virological parameters, and the indoor characteristics (ventilation rate and occupant number density). As a results of the high air exchange rate (we measured up to 180 air changes per hour) and the relatively short duration of the journey, the infection probability in cable cars traveling with open windows is remarkably lower than in other enclosed spaces such as aircraft cabins, train cars, offices, classrooms, and dining rooms. Accounting for the typical duration of the stay, the probability of infection during a cable-car ride is lower by two to three orders of magnitude than in the other examples considered (the highest risk being estimated in case of a private gathering in a poorly ventilated room). For most practical purposes, the infection probability can be approximated by the inhaled viral dose, which provides an upper bound and allows a simple comparison between different indoor situations once the air exchange rate and the occupant number density are known. Our approach and findings are applicable to any indoor space in which the viral transmission is predominately airborne and the air is well mixed.
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Affiliation(s)
- Ivan Lunati
- Laboratory of Multiscale Studies in Building Physics, EmpaDübendorfSwitzerland
| | - Claudio Mucignat
- Laboratory of Multiscale Studies in Building Physics, EmpaDübendorfSwitzerland
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22
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Stiehl B, Shrestha R, Schroeder S, Delgado J, Bazzi A, Reyes J, Kinzel M, Ahmed K. The effect of relative air humidity on the evaporation timescales of a human sneeze. AIP ADVANCES 2022; 12:075210. [PMID: 35989720 PMCID: PMC9386616 DOI: 10.1063/5.0102078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Accepted: 06/08/2022] [Indexed: 06/15/2023]
Abstract
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.
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Affiliation(s)
| | | | | | | | | | | | | | - Kareem Ahmed
- Author to whom correspondence should be addressed: . Tel.: (407) 823-5710
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23
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Kvasnicka J, Cohen Hubal EA, Siegel JA, Scott JA, Diamond ML. Modeling Clothing as a Vector for Transporting Airborne Particles and Pathogens across Indoor Microenvironments. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:5641-5652. [PMID: 35404579 PMCID: PMC9069698 DOI: 10.1021/acs.est.1c08342] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 03/19/2022] [Accepted: 03/21/2022] [Indexed: 06/14/2023]
Abstract
Evidence suggests that human exposure to airborne particles and associated contaminants, including respiratory pathogens, can persist beyond a single microenvironment. By accumulating such contaminants from air, clothing may function as a transport vector and source of "secondary exposure". To investigate this function, a novel microenvironmental exposure modeling framework (ABICAM) was developed. This framework was applied to a para-occupational exposure scenario involving the deposition of viable SARS-CoV-2 in respiratory particles (0.5-20 μm) from a primary source onto clothing in a nonhealthcare setting and subsequent resuspension and secondary exposure in a car and home. Variability was assessed through Monte Carlo simulations. The total volume of infectious particles on the occupant's clothing immediately after work was 4800 μm3 (5th-95th percentiles: 870-32 000 μm3). This value was 61% (5-95%: 17-300%) of the occupant's primary inhalation exposure in the workplace while unmasked. By arrival at the occupant's home after a car commute, relatively rapid viral inactivation on cotton clothing had reduced the infectious volume on clothing by 80% (5-95%: 26-99%). Secondary inhalation exposure (after work) was low in the absence of close proximity and physical contact with contaminated clothing. In comparison, the average primary inhalation exposure in the workplace was higher by about 2-3 orders of magnitude. It remains theoretically possible that resuspension and physical contact with contaminated clothing can occasionally transmit SARS-CoV-2 between humans.
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Affiliation(s)
- Jacob Kvasnicka
- Department
of Earth Sciences, University of Toronto, Toronto, Ontario M5S 3B1, Canada
| | - Elaine A. Cohen Hubal
- Center
for Public Health and Environmental Assessment, U.S. Environmental Protection Agency, Durham, North Carolina 27711, United States
| | - Jeffrey A. Siegel
- Department
of Civil and Mineral Engineering, University
of Toronto, Toronto, Ontario M5S 1A4, Canada
- Dalla
Lana School of Public Health, University
of Toronto, Toronto, Ontario M5T 3M7, Canada
| | - James A. Scott
- Dalla
Lana School of Public Health, University
of Toronto, Toronto, Ontario M5T 3M7, Canada
- Department
of Laboratory Medicine and Pathobiology, Temerty Faculty of Medicine, University of Toronto, 1 King’s College Circle, Toronto, Ontario M5S 1A8, Canada
| | - Miriam L. Diamond
- Department
of Earth Sciences, University of Toronto, Toronto, Ontario M5S 3B1, Canada
- Dalla
Lana School of Public Health, University
of Toronto, Toronto, Ontario M5T 3M7, Canada
- School of
the Environment, University of Toronto, Toronto, Ontario M5S 3E8, Canada
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24
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Tan S, Zhang Z, Maki K, Fidkowski KJ, Capecelatro J. Beyond well-mixed: A simple probabilistic model of airborne disease transmission in indoor spaces. INDOOR AIR 2022; 32:e13015. [PMID: 35347784 DOI: 10.1111/ina.13015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Revised: 02/21/2022] [Accepted: 02/25/2022] [Indexed: 06/14/2023]
Abstract
We develop a simple model for assessing risk of airborne disease transmission that accounts for non-uniform mixing in indoor spaces and is compatible with existing epidemiological models. A database containing 174 high-resolution simulations of airflow in classrooms, lecture halls, and buses is generated and used to quantify the spatial distribution of expiratory droplet nuclei for a wide range of ventilation rates, exposure times, and room configurations. Imperfect mixing due to obstructions, buoyancy, and turbulent dispersion results in concentration fields with significant variance. The spatial non-uniformity is found to be accurately described by a shifted lognormal distribution. A well-mixed mass balance model is used to predict the mean, and the standard deviation is parameterized based on ventilation rate and room geometry. When employed in a dose-response function risk model, infection probability can be estimated considering spatial heterogeneity that contributes to both short- and long-range transmission.
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Affiliation(s)
- Sijian Tan
- Department of Aerospace Engineering, University of Michigan, Ann Arbor, Michigan, USA
| | - Zhihang Zhang
- Department of Naval Architecture and Marine Engineering, University of Michigan, Ann Arbor, Michigan, USA
| | - Kevin Maki
- Department of Naval Architecture and Marine Engineering, University of Michigan, Ann Arbor, Michigan, USA
| | - Krzysztof J Fidkowski
- Department of Aerospace Engineering, University of Michigan, Ann Arbor, Michigan, USA
| | - Jesse Capecelatro
- Department of Aerospace Engineering, University of Michigan, Ann Arbor, Michigan, USA
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan, USA
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25
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Arpino F, Grossi G, Cortellessa G, Mikszewski A, Morawska L, Buonanno G, Stabile L. Risk of SARS-CoV-2 in a car cabin assessed through 3D CFD simulations. INDOOR AIR 2022; 32:e13012. [PMID: 35347787 PMCID: PMC9111293 DOI: 10.1111/ina.13012] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Revised: 02/09/2022] [Accepted: 02/18/2022] [Indexed: 05/26/2023]
Abstract
In this study, the risk of infection from SARS-CoV-2 Delta variant of passengers sharing a car cabin with an infected subject for a 30-min journey is estimated through an integrated approach combining a recently developed predictive emission-to-risk approach and a validated CFD numerical model numerically solved using the open-source OpenFOAM software. Different scenarios were investigated to evaluate the effect of the infected subject position within the car cabin, the airflow rate of the HVAC system, the HVAC ventilation mode, and the expiratory activity (breathing vs. speaking). The numerical simulations here performed reveal that the risk of infection is strongly influenced by several key parameters: As an example, under the same ventilation mode and emitting scenario, the risk of infection ranges from zero to roughly 50% as a function of the HVAC flow rate. The results obtained also demonstrate that (i) simplified zero-dimensional approaches limit proper evaluation of the risk in such confined spaces, conversely, (ii) CFD approaches are needed to investigate the complex fluid dynamics in similar indoor environments, and, thus, (iii) the risk of infection in indoor environments characterized by fixed seats can be in principle controlled by properly designing the flow patterns of the environment.
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Affiliation(s)
- Fausto Arpino
- Department of Civil and Mechanical EngineeringUniversity of Cassino and Southern LazioCassinoFRItaly
| | - Giorgio Grossi
- Department of Civil and Mechanical EngineeringUniversity of Cassino and Southern LazioCassinoFRItaly
| | - Gino Cortellessa
- Department of Civil and Mechanical EngineeringUniversity of Cassino and Southern LazioCassinoFRItaly
| | - Alex Mikszewski
- International Laboratory for Air Quality and HealthQueensland University of TechnologyBrisbaneQueenslandAustralia
| | - Lidia Morawska
- International Laboratory for Air Quality and HealthQueensland University of TechnologyBrisbaneQueenslandAustralia
| | - Giorgio Buonanno
- Department of Civil and Mechanical EngineeringUniversity of Cassino and Southern LazioCassinoFRItaly
- International Laboratory for Air Quality and HealthQueensland University of TechnologyBrisbaneQueenslandAustralia
| | - Luca Stabile
- Department of Civil and Mechanical EngineeringUniversity of Cassino and Southern LazioCassinoFRItaly
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26
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Conte M, Feltracco M, Chirizzi D, Trabucco S, Dinoi A, Gregoris E, Barbaro E, La Bella G, Ciccarese G, Belosi F, La Salandra G, Gambaro A, Contini D. Airborne concentrations of SARS-CoV-2 in indoor community environments in Italy. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2022; 29:13905-13916. [PMID: 34599449 PMCID: PMC8486635 DOI: 10.1007/s11356-021-16737-7] [Citation(s) in RCA: 27] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Accepted: 09/22/2021] [Indexed: 05/02/2023]
Abstract
COVID-19 pandemic raised a debate regarding the role of airborne transmission. Information regarding virus-laden aerosol concentrations is still scarce in community indoors and what are the risks for general public and the efficiency of restriction policies. This work investigates, for the first time in Italy, the presence of SARS-CoV-2 RNA in air samples collected in different community indoors (one train station, two food markets, one canteen, one shopping centre, one hair salon, and one pharmacy) in three Italian cities: metropolitan city of Venice (NE of Italy), Bologna (central Italy), and Lecce (SE of Italy). Air samples were collected during the maximum spread of the second wave of pandemic in Italy (November and December 2020). All collected samples tested negative for the presence of SARS-CoV-2, using both real-time RT-PCR and ddPCR, and no significant differences were observed comparing samples taken with and without customers. Modelling average concentrations, using influx of customers' data and local epidemiological information, indicated low values (i.e. < 0.8 copies m-3 when cotton facemasks are used and even lower for surgical facemasks). The results, even if with some limitations, suggest that the restrictive policies enforced could effectively reduce the risk of airborne transmissions in the community indoor investigated, providing that physical distance is respected.
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Affiliation(s)
- Marianna Conte
- Istituto di Scienze dell'Atmosfera e del Clima (ISAC-CNR), Str. Prv. Lecce-Monteroni km 1.2, Lecce, Italy
| | - Matteo Feltracco
- Istituto di Scienze Polari (ISP-CNR), Via Torino (Mestre), 155, Venice, Italy
- Dipartimento di Scienze Ambientali, Informatica e Statistica, Università Ca' Foscari di Venezia, Via Torino (Mestre), 155, Venezia, Italy
| | - Daniela Chirizzi
- Istituto Zooprofilattico Sperimentale della Puglia e della Basilicata (IZSPB), Via Manfredonia, 20, Foggia, Italy
| | - Sara Trabucco
- Istituto di Scienze dell'Atmosfera e del Clima (ISAC-CNR), Via Gobetti, 101, Bologna, Italy
| | - Adelaide Dinoi
- Istituto di Scienze dell'Atmosfera e del Clima (ISAC-CNR), Str. Prv. Lecce-Monteroni km 1.2, Lecce, Italy
| | - Elena Gregoris
- Istituto di Scienze Polari (ISP-CNR), Via Torino (Mestre), 155, Venice, Italy
- Dipartimento di Scienze Ambientali, Informatica e Statistica, Università Ca' Foscari di Venezia, Via Torino (Mestre), 155, Venezia, Italy
| | - Elena Barbaro
- Istituto di Scienze Polari (ISP-CNR), Via Torino (Mestre), 155, Venice, Italy
- Dipartimento di Scienze Ambientali, Informatica e Statistica, Università Ca' Foscari di Venezia, Via Torino (Mestre), 155, Venezia, Italy
| | - Gianfranco La Bella
- Istituto Zooprofilattico Sperimentale della Puglia e della Basilicata (IZSPB), Via Manfredonia, 20, Foggia, Italy
| | - Giuseppina Ciccarese
- Istituto Zooprofilattico Sperimentale della Puglia e della Basilicata (IZSPB), Via Manfredonia, 20, Foggia, Italy
| | - Franco Belosi
- Istituto di Scienze dell'Atmosfera e del Clima (ISAC-CNR), Via Gobetti, 101, Bologna, Italy
| | - Giovanna La Salandra
- Istituto Zooprofilattico Sperimentale della Puglia e della Basilicata (IZSPB), Via Manfredonia, 20, Foggia, Italy
| | - Andrea Gambaro
- Dipartimento di Scienze Ambientali, Informatica e Statistica, Università Ca' Foscari di Venezia, Via Torino (Mestre), 155, Venezia, Italy
| | - Daniele Contini
- Istituto di Scienze dell'Atmosfera e del Clima (ISAC-CNR), Str. Prv. Lecce-Monteroni km 1.2, Lecce, Italy.
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Investigation on the evaporation and dispersion of human respiratory droplets with COVID-19 virus. INTERNATIONAL JOURNAL OF MULTIPHASE FLOW 2022; 147. [PMCID: PMC8603237 DOI: 10.1016/j.ijmultiphaseflow.2021.103904] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
On March 11, 2020, COVID-19 was declared as a pandemic by World Health Organization (WHO). Effective prevention is indispensable for defeating the ongoing COVID-19 pandemic. The evaporation and diffusion characteristics of the droplet in the air are the critical factors for the virus transmission by droplets. To better understand transmission routes of COVID-19 through respiratory droplets, a new evaporation and dispersion model for respiratory droplets is proposed to estimate droplet lifetime and the size of spreading zone in air. The importance of respiratory activities and environmental factors on the transmission of respiratory viruses are further discussed. The predictive results demonstrate initial particle size, ambient temperature and relative humidity all have significant effect on the survival time and infection distance of respiratory droplets. Decreasing droplet initial size always shortens the lifetime and the transmission distance of respiratory droplets. The 100 μm droplets expelled by talking or coughing can be carried more than 2 m away. Increasing ambient temperature and decreasing ambient humidity can effectively reduce the lifetime and propagation distance of respiratory droplets, thus reducing the risk of viral infection. These findings could contribute to developing effective prevention measures for controlling infectious disease transmission via droplets.
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28
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Auvinen M, Kuula J, Grönholm T, Sühring M, Hellsten A. High-resolution large-eddy simulation of indoor turbulence and its effect on airborne transmission of respiratory pathogens-Model validation and infection probability analysis. PHYSICS OF FLUIDS (WOODBURY, N.Y. : 1994) 2022; 34:015124. [PMID: 35340682 PMCID: PMC8939551 DOI: 10.1063/5.0076495] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2021] [Accepted: 12/10/2021] [Indexed: 05/18/2023]
Abstract
High-resolution large-eddy simulation (LES) is exploited to study indoor air turbulence and its effect on the dispersion of respiratory virus-laden aerosols and subsequent transmission risks. The LES modeling is carried out with unprecedented accuracy and subsequent analysis with novel mathematical robustness. To substantiate the physical relevance of the LES model under realistic ventilation conditions, a set of experimental aerosol concentration measurements are carried out, and their results are used to successfully validate the LES model results. The obtained LES dispersion results are subjected to pathogen exposure and infection probability analysis in accordance with the Wells-Riley model, which is here mathematically extended to rely on LES-based space- and time-dependent concentration fields. The methodology is applied to assess two dissimilar approaches to reduce transmission risks: a strategy to augment the indoor ventilation capacity with portable air purifiers and a strategy to utilize partitioning by exploiting portable space dividers. The LES results show that use of air purifiers leads to greater reduction in absolute risks compared to the analytical Wells-Riley model, which fails to predict the original risk level. However, the two models do agree on the relative risk reduction. The spatial partitioning strategy is demonstrated to have an undesirable effect when employed without other measures, but may yield desirable outcomes with targeted air purifier units. The study highlights the importance of employing accurate indoor turbulence modeling when evaluating different risk-reduction strategies.
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Affiliation(s)
- Mikko Auvinen
- Finnish Meteorological Institute, Erik Palmenin aukio 1, 00560 Helsinki, Finland
- Author to whom correspondence should be addressed:
| | - Joel Kuula
- Finnish Meteorological Institute, Erik Palmenin aukio 1, 00560 Helsinki, Finland
| | - Tiia Grönholm
- Finnish Meteorological Institute, Erik Palmenin aukio 1, 00560 Helsinki, Finland
| | - Matthias Sühring
- Institute of Meteorology and Climatology, Leibniz University Hannover, Herrenhäuser Strasse 2, 30419 Hannover, Germany
| | - Antti Hellsten
- Finnish Meteorological Institute, Erik Palmenin aukio 1, 00560 Helsinki, Finland
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29
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Wang J, Dalla Barba F, Roccon A, Sardina G, Soldati A, Picano F. Modelling the direct virus exposure risk associated with respiratory events. J R Soc Interface 2022; 19:20210819. [PMID: 35016556 PMCID: PMC8753145 DOI: 10.1098/rsif.2021.0819] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Accepted: 12/13/2021] [Indexed: 12/14/2022] Open
Abstract
The outbreak of the COVID-19 pandemic highlighted the importance of accurately modelling the pathogen transmission via droplets and aerosols emitted while speaking, coughing and sneezing. In this work, we present an effective model for assessing the direct contagion risk associated with these pathogen-laden droplets. In particular, using the most recent studies on multi-phase flow physics, we develop an effective yet simple framework capable of predicting the infection risk associated with different respiratory activities in different ambient conditions. We start by describing the mathematical framework and benchmarking the model predictions against well-assessed literature results. Then, we provide a systematic assessment of the effects of physical distancing and face coverings on the direct infection risk. The present results indicate that the risk of infection is vastly impacted by the ambient conditions and the type of respiratory activity, suggesting the non-existence of a universal safe distance. Meanwhile, wearing face masks provides excellent protection, effectively limiting the transmission of pathogens even at short physical distances, i.e. 1 m.
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Affiliation(s)
- Jietuo Wang
- Centro di Ateneo di Studi e Attività Spaziali - CISAS, University of Padova, Padova 35131, Italy
| | | | - Alessio Roccon
- Institute of Fluid Mechanics and Heat Transfer, TU Wien, Vienna 1060, Austria
- Polytechnic Department, University of Udine, 33100 Udine, Italy
| | - Gaetano Sardina
- Department of Mechanics and Maritime Sciences, Chalmers University of Technology, 41296 Gothenburg, Sweden
| | - Alfredo Soldati
- Institute of Fluid Mechanics and Heat Transfer, TU Wien, Vienna 1060, Austria
- Polytechnic Department, University of Udine, 33100 Udine, Italy
| | - Francesco Picano
- Centro di Ateneo di Studi e Attività Spaziali - CISAS, University of Padova, Padova 35131, Italy
- Department of Industrial Engineering, University of Padova, Padova 35131, Italy
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30
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Deng Z, Chen Q. What is suitable social distancing for people wearing face masks during the COVID-19 pandemic? INDOOR AIR 2022; 32:e12935. [PMID: 34605574 PMCID: PMC8652892 DOI: 10.1111/ina.12935] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 09/05/2021] [Accepted: 09/18/2021] [Indexed: 05/06/2023]
Abstract
COVID-19 has caused the global pandemic and had a serious impact on people's daily lives. The respiratory droplets produced from coughing and talking of an infected patient were possible transmission routes of coronavirus between people. To avoid the infection, the US Centers for Disease Control and Prevention (CDC) advised to wear face masks while maintaining a social distancing of 2 m. Can the social distancing be reduced if people wear masks? To answer this question, we measured the mass of inhaled droplets by a susceptible manikin wearing a mask with different social distances, which was produced by coughing and talking of an index "patient" (human subject) also wearing a mask. We also used the computational fluid dynamics (CFD) technology with a porous media model and particle dispersion model to simulate the transmission of droplets from the patient to the susceptible person with surgical and N95 masks. We compared the CFD results with the measured velocity in the environmental chamber and found that the social distancing could be reduced to 0.5 m when people wearing face masks. In this case, the mass concentration of inhaled particles was less than two people without wearing masks and with a social distancing of 2 m. Hence, when the social distancing was difficult, wearing masks could protect people. We also found that the leakage between the face mask and the human face played an important role in the exhaled airflow pattern and particle dispersion. The verified numerical model can be used for more scenarios with different indoor environments and HVAC systems. The results of this study would make business profitable with reduced social distancing in transportation, education, and entertainment industries, which was beneficial for the reopening of the economy.
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Affiliation(s)
- Zhipeng Deng
- School of Mechanical EngineeringPurdue UniversityWest LafayetteINUSA
| | - Qingyan Chen
- Department of Building Environment and Energy EngineeringThe Hong Kong Polytechnic UniversityKowloonHong Kong
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31
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Olivieri S, Cavaiola M, Mazzino A, Rosti ME. Transport and evaporation of virus-containing droplets exhaled by men and women in typical cough events. MECCANICA 2022; 57:567-575. [PMID: 35039689 PMCID: PMC8754081 DOI: 10.1007/s11012-021-01469-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Accepted: 12/13/2021] [Indexed: 05/19/2023]
Abstract
The spreading of the virus-containing droplets exhaled during respiratory events, e.g., cough, is an issue of paramount importance for the prevention of many infections such as COVID-19. According to the scientific literature, remarkable differences can be ascribed to several parameters that govern such complex and multiphysical problem. Among these, a particular influence appears associated with the different airflows typical of male and female subjects. Focusing on a typical cough event, we investigate this aspect by means of highly-resolved direct numerical simulations of the turbulent airflow in combination with a comprehensive Lagrangian particle tracking model for the droplet motion and evaporation. We observe and quantify major differences between the case of male and female subjects, both in terms of the droplet final reach and evaporation time. Our results can be associated with the different characteristics in the released airflow and thus confirm the influence of the subject gender (or other physical properties providing different exhalation profiles) on both short-range and long-range airborne transmission.
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Affiliation(s)
- Stefano Olivieri
- Complex Fluids and Flows Unit, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna-son, Okinawa 904-0495 Japan
| | - Mattia Cavaiola
- INFN and Department of Civil, Chemical and Environmental Engineering (DICCA), University of Genova, Via Montallegro 1, 16145 Genova, Italy
| | - Andrea Mazzino
- INFN and Department of Civil, Chemical and Environmental Engineering (DICCA), University of Genova, Via Montallegro 1, 16145 Genova, Italy
| | - Marco E. Rosti
- Complex Fluids and Flows Unit, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna-son, Okinawa 904-0495 Japan
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32
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Mehade Hussain S, Goel S, Kadapa C, Aristodemou E. A short review of vapour droplet dispersion models used in CFD to study the airborne spread of COVID19. MATERIALS TODAY: PROCEEDINGS 2022; 64:1349-1356. [PMID: 35495177 PMCID: PMC9035368 DOI: 10.1016/j.matpr.2022.03.724] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The use of computational fluid dynamics (CFD) to simulate the spread of COVID19 and many other airborne diseases, especially in an indoor environment needs accurate understanding of dispersion models. Modelling the transport/dispersion of vapour droplets within the atmosphere is a complex problem, as it involves the motion of more than one phase, as well as the interphase interactions between the phases. This paper reviews the current canon of research on dispersion modelling of vapour droplets by looking at three specific aspects: (i) physical definition/specification of the initial droplet size distribution; (ii) physics of evaporation/condensation models and (iii) transport equations (with molecular/turbulent dispersion models) to describe the movement of the vapour droplets as they propagate through the air. This review found that the state of modelling implements a wide range of models which shows variances in results thus leading to a state where it is difficult to know which model is most accurate. The authors suggest that further studies in this direction should focus on developing a principle set of equations by benchmarking the previously developed models to establish model uncertainty of the previously developed models with reference to a fixed theoretical model and be compared under identical conditions. However, it must be noted that due to the complex nature of microdroplet evaporation and dispersion coupled with the unpredictable way droplet size distributions are produced, current experimental methodologies that are available to validate such simulations, such as particle image velocimetry, are still not robust enough to provide detailed data to verify minute aspects of the simulations.
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Affiliation(s)
| | - Saurav Goel
- School of Engineering, London South Bank University, London SE10 AA, UK
- University of Petroleum and Energy Studies, Dehradun 248007, India
- Indian Institute of Technology Guwahati, Guwahati 781039, India
| | | | - Elsa Aristodemou
- School of Engineering, London South Bank University, London SE10 AA, UK
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33
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Randall K, Ewing ET, Marr LC, Jimenez JL, Bourouiba L. How did we get here: what are droplets and aerosols and how far do they go? A historical perspective on the transmission of respiratory infectious diseases. Interface Focus 2021; 11:20210049. [PMID: 34956601 PMCID: PMC8504878 DOI: 10.1098/rsfs.2021.0049] [Citation(s) in RCA: 53] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/13/2021] [Indexed: 12/19/2022] Open
Abstract
The COVID-19 pandemic has exposed major gaps in our understanding of the transmission of viruses through the air. These gaps slowed recognition of airborne transmission of the disease, contributed to muddled public health policies and impeded clear messaging on how best to slow transmission of COVID-19. In particular, current recommendations have been based on four tenets: (i) respiratory disease transmission routes can be viewed mostly in a binary manner of ‘droplets’ versus ‘aerosols’; (ii) this dichotomy depends on droplet size alone; (iii) the cut-off size between these routes of transmission is 5 µm; and (iv) there is a dichotomy in the distance at which transmission by each route is relevant. Yet, a relationship between these assertions is not supported by current scientific knowledge. Here, we revisit the historical foundation of these notions, and how they became entangled from the 1800s to today, with a complex interplay among various fields of science and medicine. This journey into the past highlights potential solutions for better collaboration and integration of scientific results into practice for building a more resilient society with more sound, far-sighted and effective public health policies.
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Affiliation(s)
- K Randall
- Department of Civil & Environmental Engineering, Virginia Tech, Blacksburg, VA, USA
| | - E T Ewing
- Department of Civil & Environmental Engineering, Virginia Tech, Blacksburg, VA, USA
| | - L C Marr
- Department of Civil & Environmental Engineering, Virginia Tech, Blacksburg, VA, USA
| | - J L Jimenez
- Department of Chemistry and CIRES, University of Colorado, Boulder, CO, USA
| | - L Bourouiba
- Fluid Dynamics of Disease Transmission Laboratory, Massachusetts Institute of Technology, Cambridge, MA, USA
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34
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Influence of ambient conditions on evaporation and transport of respiratory droplets in indoor environment. INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER 2021; 129. [PMCID: PMC8577817 DOI: 10.1016/j.icheatmasstransfer.2021.105750] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Respiratory droplets are playing a significant role in the transmission of any flu type disease as well as SARS-Cov-2 virus. The presence of pathogens affects the evaporation of the liquid droplets along with ambient temperature and relative humidity (rh). Complete evaporation of droplets leads to the formation of aerosol or droplet nuclei which remain suspended in the air for a longer period of time and get spread over larger distances increasing the risk of disease transmission. In present work, a droplet evaporation model has been formulated considering the droplet as a salt solution and the formation of crystals has been taken into account which will be analogous to the aerosol formation. After the establishment of the evaporation model, the trajectories of the droplets are investigated considering a turbulent round jet model during exhalation. Aerosols are found to be spreading over distances of 8 to 9 m which is quite alarming. Large droplets get converted to smaller ones but the viral loading of the large droplets is much higher than the smaller as viral loading is proportional to initial size. This is highlighted by the viral load contour and the mean diameter line contour for a half-height window. Different weather conditions are investigated to observe the evaporation of droplets and the formation of aerosols in order to qualitatively analyse the risks associated with each city in specific weather conditions. Hot and dry conditions are most favourable to aerosol formation.
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35
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Calmet H, Inthavong K, Both A, Surapaneni A, Mira D, Egukitza B, Houzeaux G. Large eddy simulation of cough jet dynamics, droplet transport, and inhalability over a ten minute exposure. PHYSICS OF FLUIDS (WOODBURY, N.Y. : 1994) 2021; 33:125122. [PMID: 35002205 PMCID: PMC8728631 DOI: 10.1063/5.0072148] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Accepted: 11/28/2021] [Indexed: 06/14/2023]
Abstract
High fidelity simulations of expiratory events such as coughing provide the opportunity to predict the fate of the droplets from the turbulent jet cloud produced from a cough. It is well established that droplets carrying infectious pathogens with diameters of 1 - 5 μ m remain suspended in the air for several hours and transported by the air currents over considerable distances (e.g., in meters). This study used a highly resolved mesh to capture the multiphase turbulent buoyant cloud with suspended droplets produced by a cough. The cough droplets' dispersion was subjected to thermal gradients and evaporation and allowed to disperse between two humans standing 2 m apart. A nasal cavity anatomy was included inside the second human to determine the inhaled droplets. Three diameter ranges characterized the droplet cloud, < 5 μ m , which made up 93% of all droplets by number; 5 to 100 μm comprised 3%, and > 100 μ m comprising 4%. The results demonstrated the temporal evolution of the cough event, where a jet is first formed, followed by a thermally driven puff cloud with the latter primarily composed of droplets under 5 μm diameter, moving with a vortex string structure. After the initial cough, the data were interpolated onto a more coarse mesh to allow the simulation to cover ten minutes, equivalent to 150 breathing cycles. We observe that the critical diameter size susceptible to inhalation was 0.5 μ m , although most inhaled droplets after 10 min by the second human were approximately 0.8 μ m . These observations offer insight into the risk of airborne transmission and numerical metrics for modeling and risk assessment.
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Affiliation(s)
- Hadrien Calmet
- Department of Computer Applications in Science and Engineering, Barcelona Supercomputing Center (BSC-CNS), Barcelona, Spain
| | - Kiao Inthavong
- Mechanical & Automotive Engineering, School of Engineering, RMIT University, Melbourne, Australia
| | - Ambrus Both
- Department of Computer Applications in Science and Engineering, Barcelona Supercomputing Center (BSC-CNS), Barcelona, Spain
| | - Anurag Surapaneni
- Department of Computer Applications in Science and Engineering, Barcelona Supercomputing Center (BSC-CNS), Barcelona, Spain
| | - Daniel Mira
- Department of Computer Applications in Science and Engineering, Barcelona Supercomputing Center (BSC-CNS), Barcelona, Spain
| | - Beatriz Egukitza
- Department of Computer Applications in Science and Engineering, Barcelona Supercomputing Center (BSC-CNS), Barcelona, Spain
| | - Guillaume Houzeaux
- Department of Computer Applications in Science and Engineering, Barcelona Supercomputing Center (BSC-CNS), Barcelona, Spain
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36
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Cortellessa G, Stabile L, Arpino F, Faleiros DE, van den Bos W, Morawska L, Buonanno G. Close proximity risk assessment for SARS-CoV-2 infection. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 794:148749. [PMID: 34225157 PMCID: PMC8242194 DOI: 10.1016/j.scitotenv.2021.148749] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Revised: 06/23/2021] [Accepted: 06/25/2021] [Indexed: 05/04/2023]
Abstract
Although the interpersonal distance represents an important parameter affecting the risk of infection due to respiratory viruses, the mechanism of exposure to exhaled droplets remains insufficiently characterized. In this study, an integrated risk assessment is presented for SARS-CoV-2 close proximity exposure between a speaking infectious subject and a susceptible subject. It is based on a three-dimensional transient numerical model for the description of exhaled droplet spread once emitted by a speaking person, coupled with a recently proposed SARS-CoV-2 emission approach. Particle image velocimetry measurements were conducted to validate the numerical model. The contribution of the large droplets to the risk is barely noticeable only for distances well below 0.6 m, whereas it drops to zero for greater distances where it depends only on airborne droplets. In particular, for short exposures (10 s) a minimum safety distance of 0.75 m should be maintained to lower the risk below 0.1%; for exposures of 1 and 15 min this distance increases to about 1.1 and 1.5 m, respectively. Based on the interpersonal distances across countries reported as a function of interacting individuals, cultural differences, and environmental and sociopsychological factors, the approach presented here revealed that, in addition to intimate and personal distances, particular attention must be paid to exposures longer than 1 min within social distances (of about 1 m).
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Affiliation(s)
- G Cortellessa
- Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Cassino, FR, Italy
| | - L Stabile
- Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Cassino, FR, Italy
| | - F Arpino
- Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Cassino, FR, Italy
| | - D E Faleiros
- Maritime and Transport Technology, TU Delft, Netherlands
| | - W van den Bos
- Maritime and Transport Technology, TU Delft, Netherlands
| | - L Morawska
- International Laboratory for Air Quality and Health, Queensland University of Technology, Brisbane, Qld, Australia
| | - G Buonanno
- Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Cassino, FR, Italy; International Laboratory for Air Quality and Health, Queensland University of Technology, Brisbane, Qld, Australia.
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37
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Trivedi S, Gkantonas S, Mesquita LCC, Iavarone S, de Oliveira PM, Mastorakos E. Estimates of the stochasticity of droplet dispersion by a cough. PHYSICS OF FLUIDS (WOODBURY, N.Y. : 1994) 2021; 33:115130. [PMID: 35002201 PMCID: PMC8726635 DOI: 10.1063/5.0070528] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Accepted: 10/24/2021] [Indexed: 06/01/2023]
Abstract
In this paper, the statistical distributions of the position and the size of the evaporating droplets after a cough are evaluated, thus characterizing the inherent stochasticity of respiratory releases due to turbulence. For that, ten independent realizations of a cough with realistic initial conditions and in a room at 20 °C and 40% relative humidity were performed with large eddy simulations and Lagrangian tracking of the liquid phase. It was found that although turbulence decreases far from the emitter, it results in large variations in the spatial distribution of the droplets. The total suspended liquid mass after 60 s from the cough is in good agreement with that estimated by a one-dimensional model accounting for settling and evaporation under quiescent conditions, while deposition times of droplets in the 10-100 μm range are found to vary significantly, reflected in the mass of liquid, and hence the virus content, potentially inhaled by a receptor. The high variability between events is due to the local fluctuations of temperature, humidity, and velocity on droplet evaporation and motion. The droplet distribution suggests that, in the absence of face coverings, an unprotected cough is not safe at 2 m away from the emitter even outdoors. The results indicate that mitigation measures, such as ventilation to address long-range transmission, can be based on the total suspended liquid content evaluated from reduced-order models. However, the large variability of viral content in the near field produces wide variations in estimates of risk; therefore, a stochastic approach is needed for evaluating short-range transmission risk.
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Affiliation(s)
- Shrey Trivedi
- Department of Engineering, University of Cambridge, Trumpington Street, Cambridge CB2 1PZ, United Kingdom
| | - Savvas Gkantonas
- Department of Engineering, University of Cambridge, Trumpington Street, Cambridge CB2 1PZ, United Kingdom
| | - Léo C. C. Mesquita
- Department of Engineering, University of Cambridge, Trumpington Street, Cambridge CB2 1PZ, United Kingdom
| | - Salvatore Iavarone
- Department of Engineering, University of Cambridge, Trumpington Street, Cambridge CB2 1PZ, United Kingdom
| | - Pedro M. de Oliveira
- Department of Engineering, University of Cambridge, Trumpington Street, Cambridge CB2 1PZ, United Kingdom
| | - Epaminondas Mastorakos
- Department of Engineering, University of Cambridge, Trumpington Street, Cambridge CB2 1PZ, United Kingdom
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38
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Behera S, Bhardwaj R, Agrawal A. Effect of co-flow on fluid dynamics of a cough jet with implications in spread of COVID-19. PHYSICS OF FLUIDS (WOODBURY, N.Y. : 1994) 2021; 33:101701. [PMID: 34737529 PMCID: PMC8561654 DOI: 10.1063/5.0064104] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Accepted: 08/20/2021] [Indexed: 05/12/2023]
Abstract
We discuss the temporal evolution of a cough jet of an infected subject in the context of the spread of COVID-19. Computations were carried out using large eddy simulation, and, in particular, the effect of the co-flow (5% and 10% of maximum cough velocity) on the evolution of the jet was quantified. The Reynolds number (Re) of the cough jet, based on the mouth opening diameter (D) and the average cough velocity, is 13 002. The time-varying inlet velocity profile of the cough jet is represented as a combination of gamma-probability-distribution functions. Simulations reveal the detailed structure of cough jet with and without a co-flow for the first time, to the best of our knowledge. The cough jet temporal evolution is similar to that of a continuous free-jet and follows the same routes of instability, as documented for a free-jet. The convection velocity of the cough jet decays with time and distance, following a power-law variation. The cough jet is observed to travel a distance of approximately 1.1 m in half a second. However, in the presence of 10% co-flow, the cough jet travels faster and covers the similar distance in just 0.33 s. Therefore, in the presence of a co-flow, the probability of transmission of COVID-19 by airborne droplets and droplet nuclei increases, since they can travel a larger distance. The cough jet without the co-flow corresponds to a larger volume content compared to that with the co-flow and spreads more within the same range of distance. These simulations are significant as they help to reveal the intricate structure of the cough jet and show that the presence of a co-flow can significantly augment the risk of infection of COVID-19.
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Affiliation(s)
- Sachidananda Behera
- Department of Mechanical Engineering, Indian Institute of Technology
Bombay, Mumbai 400076, India
| | - Rajneesh Bhardwaj
- Department of Mechanical Engineering, Indian Institute of Technology
Bombay, Mumbai 400076, India
| | - Amit Agrawal
- Department of Mechanical Engineering, Indian Institute of Technology
Bombay, Mumbai 400076, India
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39
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Pourfattah F, Wang LP, Deng W, Ma YF, Hu L, Yang B. Challenges in simulating and modeling the airborne virus transmission: A state-of-the-art review. PHYSICS OF FLUIDS (WOODBURY, N.Y. : 1994) 2021; 33:101302. [PMID: 34803360 PMCID: PMC8597718 DOI: 10.1063/5.0061469] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2021] [Accepted: 10/04/2021] [Indexed: 06/09/2023]
Abstract
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.
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Affiliation(s)
- Farzad Pourfattah
- Guangdong Provincial Key Laboratory of Turbulence Research and Applications, Center for Complex Flows and Soft Matter Research and Department of Mechanics and Aerospace Engineering, Southern University of Science and Technology, Shenzhen 518055, People's Republic of China
| | | | - Weiwei Deng
- Guangdong Provincial Key Laboratory of Turbulence Research and Applications, Center for Complex Flows and Soft Matter Research and Department of Mechanics and Aerospace Engineering, Southern University of Science and Technology, Shenzhen 518055, People's Republic of China
| | - Yong-Feng Ma
- Guangdong Provincial Key Laboratory of Turbulence Research and Applications, Center for Complex Flows and Soft Matter Research and Department of Mechanics and Aerospace Engineering, Southern University of Science and Technology, Shenzhen 518055, People's Republic of China
| | - Liangquan Hu
- Guangdong Provincial Key Laboratory of Turbulence Research and Applications, Center for Complex Flows and Soft Matter Research and Department of Mechanics and Aerospace Engineering, Southern University of Science and Technology, Shenzhen 518055, People's Republic of China
| | - Bo Yang
- Guangdong Provincial Key Laboratory of Turbulence Research and Applications, Center for Complex Flows and Soft Matter Research and Department of Mechanics and Aerospace Engineering, Southern University of Science and Technology, Shenzhen 518055, People's Republic of China
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Quantitative modeling of the impact of facemasks and associated leakage on the airborne transmission of SARS-CoV-2. Sci Rep 2021; 11:19403. [PMID: 34593891 PMCID: PMC8484595 DOI: 10.1038/s41598-021-98895-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2021] [Accepted: 09/16/2021] [Indexed: 12/28/2022] Open
Abstract
The ongoing worldwide outbreak of COVID-19 has set personal protective equipment in the spotlight. A significant number of countries impose the use of facemasks in public spaces and encourage it in the private sphere. Even in countries where relatively high vaccination rates are achieved at present, breakthrough infections have been frequently reported and usage of facemasks in certain settings has been recommended again. Alternative solutions, including community masks fabricated using various materials, such as cotton or jersey, have emerged alongside facemasks following long-established standards (e.g., EN 149, EN 14683). In the present work, we present a computational model to calculate the ability of different types of facemasks to reduce the exposure to virus-laden respiratory particles, with a focus on the relative importance of the filtration properties and the fitting on the wearer’s face. The model considers the facemask and the associated leakage, the transport of respiratory particles and their accumulation around the emitter, as well as the fraction of the inhaled particles deposited in the respiratory system. Different levels of leakages are considered to represent the diversity of fittings likely to be found among a population of non-trained users. The leakage prevails over the filtration performance of a facemask in determining the exposure level, and the ability of a face protection to limit leakages needs to be taken into account to accurately estimate the provided protection. Filtering facepieces (FFP) provide a better protection efficiency than surgical and community masks due to their higher filtration efficiency and their ability to provide a better fit and thus reduce the leakages. However, an improperly-fitted FFP mask loses a critical fraction of its protection efficiency, which may drop below the protection level provided by properly-worn surgical and community masks.
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Dabiri D, Conti SR, Sadoughi Pour N, Chong A, Dadjoo S, Dabiri D, Wiese C, Badal J, Hoogland MA, Conti HR, Taylor TR, Choueiri G, Amili O. A Multi-Disciplinary Review on the Aerobiology of COVID-19 in Dental Settings. FRONTIERS IN DENTAL MEDICINE 2021; 2. [PMID: 35574425 PMCID: PMC9098049 DOI: 10.3389/fdmed.2021.726395] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The COVID-19 pandemic pushed dental health officials around the world to reassess and adjust their existing healthcare practices. As studies on controlled COVID-19 transmission remain challenging, this review focuses on particles that can carry the virus and relevant approaches to mitigate the risk of pathogen transmission in dental offices. This review gives an overview of particles generated in clinical settings and how size influences their distribution, concentration, and generation route. A wide array of pertinent particle characterization and counting methods are reviewed, along with their working range, reliability, and limitations. This is followed by a focus on the effectiveness of personal protective equipment (PPE) and face shields in protecting patients and dentists from aerosols. Direct studies on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are still limited, but the literature supports the use of masks as an important and effective non-pharmaceutical preventive measure that could reduce the risk of contracting a respiratory infection by up to 20%. In addition to discussing about PPE used by most dental care professionals, this review describes other ways by which dental offices can protect patients and dental office personnel, which includes modification of the existing room design, dental equipment, and heating, ventilation, and air conditioning (HVAC) system. More affordable modifications include positioning a high-efficiency particulate air (HEPA) unit within proximity of the patient’s chair or using ultraviolet germicidal irradiation in conjunction with ventilation. Additionally, portable fans could be used to direct airflow in one direction, first through the staff working areas and then through the patient treatment areas, which could decrease the number of airborne particles in dental offices. This review concludes that there is a need for greater awareness amongst dental practitioners about the relationship between particle dynamics and clinical dentistry, and additional research is needed to fill the broad gaps of knowledge in this field.
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Affiliation(s)
- Darya Dabiri
- Department of Dentistry, Division of Pediatric Dentistry, University of Toledo, Toledo, OH, United States
- Correspondence: Darya Dabiri,
| | - Samuel Richard Conti
- Department of Biological Sciences, University of Toledo, Toledo, OH, United States
| | - Niloufar Sadoughi Pour
- Department of Mechanical, Industrial and Manufacturing Engineering (MIME), University of Toledo, Toledo, OH, United States
| | - Andrew Chong
- Department of Cariology, Restorative Sciences & Endodontics, University of Michigan, Ann Arbor, MI, United States
| | - Shaahin Dadjoo
- Department of Orthodontics and Dentofacial Orthopedics, The Eastman Institute for Oral Health, University of Rochester, Rochester, NY, United States
| | - Donya Dabiri
- Department of Dentistry, Division of Pediatric Dentistry, University of Toledo, Toledo, OH, United States
| | - Carol Wiese
- Department of Dentistry, Division of Pediatric Dentistry, University of Toledo, Toledo, OH, United States
| | - Joyce Badal
- Department of Medicine, University of Toledo, Toledo, OH, United States
| | | | - Heather Raquel Conti
- Department of Biological Sciences, University of Toledo, Toledo, OH, United States
| | - Travis Roger Taylor
- Department of Medical Microbiology and Immunology, University of Toledo, Toledo, OH, United States
| | - George Choueiri
- Department of Mechanical, Industrial and Manufacturing Engineering (MIME), University of Toledo, Toledo, OH, United States
| | - Omid Amili
- Department of Mechanical, Industrial and Manufacturing Engineering (MIME), University of Toledo, Toledo, OH, United States
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Short-range exposure to airborne virus transmission and current guidelines. Proc Natl Acad Sci U S A 2021; 118:2105279118. [PMID: 34465564 DOI: 10.1073/pnas.2105279118] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
After the Spanish flu pandemic, it was apparent that airborne transmission was crucial to spreading virus contagion, and research responded by producing several fundamental works like the experiments of Duguid [J. P. Duguid, J. Hyg. 44, 6 (1946)] and the model of Wells [W. F. Wells, Am. J. Hyg. 20, 611-618 (1934)]. These seminal works have been pillars of past and current guidelines published by health organizations. However, in about one century, understanding of turbulent aerosol transport by jets and plumes has enormously progressed, and it is now time to use this body of developed knowledge. In this work, we use detailed experiments and accurate computationally intensive numerical simulations of droplet-laden turbulent puffs emitted during sneezes in a wide range of environmental conditions. We consider the same emission-number of drops, drop size distribution, and initial velocity-and we change environmental parameters such as temperature and humidity, and we observe strong variation in droplets' evaporation or condensation in accordance with their local temperature and humidity microenvironment. We assume that 3% of the initial droplet volume is made of nonvolatile matter. Our systematic analysis confirms that droplets' lifetime is always about one order of magnitude larger compared to previous predictions, in some cases up to 200 times. Finally, we have been able to produce original virus exposure maps, which can be a useful instrument for health scientists and practitioners to calibrate new guidelines to prevent short-range airborne disease transmission.
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Abstract
The host-to-host transmission of respiratory infectious diseases is fundamentally enabled by the interaction of pathogens with a variety of fluids (gas or liquid) that shape pathogen encapsulation and emission, transport and persistence in the environment, and new host invasion and infection. Deciphering the mechanisms and fluid properties that govern and promote these steps of pathogen transmission will enable better risk assessment and infection control strategies, and may reveal previously underappreciated ways in which the pathogens might actually adapt to or manipulate the physical and chemical characteristics of these carrier fluids to benefit their own transmission. In this article, I review our current understanding of the mechanisms shaping the fluid dynamics of respiratory infectious diseases.
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Affiliation(s)
- Lydia Bourouiba
- The Fluid Dynamics of Disease Transmission Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA;
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Katre P, Banerjee S, Balusamy S, Sahu KC. Fluid dynamics of respiratory droplets in the context of COVID-19: Airborne and surfaceborne transmissions. PHYSICS OF FLUIDS (WOODBURY, N.Y. : 1994) 2021; 33:081302. [PMID: 34471333 PMCID: PMC8404377 DOI: 10.1063/5.0063475] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Accepted: 08/03/2021] [Indexed: 05/19/2023]
Abstract
The World Health Organization has declared COVID-19 a global pandemic. Several countries have experienced repeated periods of major spreading over the last two years. Many people have lost their lives, employment, and the socioeconomic situation has been severely impacted. Thus, it is considered to be one of the major health and economic disasters in modern history. Over the last two years, several researchers have contributed significantly to the study of droplet formation, transmission, and lifetime in the context of understanding the spread of such respiratory infections from a fluid dynamics perspective. The current review emphasizes the numerous ways in which fluid dynamics aids in the comprehension of these aspects. The biology of the virus, as well as other statistical studies to forecast the pandemic, is significant, but they are not included in this review.
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Affiliation(s)
- Pallavi Katre
- Department of Chemical Engineering, Indian Institute of Technology Hyderabad, Sangareddy 502285, Telangana, India
| | - Sayak Banerjee
- Department of Mechanical and Aerospace Engineering, Indian Institute of Technology Hyderabad, Sangareddy 502285, Telangana, India
| | - Saravanan Balusamy
- Department of Mechanical and Aerospace Engineering, Indian Institute of Technology Hyderabad, Sangareddy 502285, Telangana, India
| | - Kirti Chandra Sahu
- Department of Chemical Engineering, Indian Institute of Technology Hyderabad, Sangareddy 502285, Telangana, India
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Shen J, Kong M, Dong B, Birnkrant MJ, Zhang J. A systematic approach to estimating the effectiveness of multi-scale IAQ strategies for reducing the risk of airborne infection of SARS-CoV-2. BUILDING AND ENVIRONMENT 2021; 200:107926. [PMID: 33967376 PMCID: PMC8084626 DOI: 10.1016/j.buildenv.2021.107926] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Revised: 04/04/2021] [Accepted: 04/24/2021] [Indexed: 05/05/2023]
Abstract
The unprecedented coronavirus disease 2019 (COVID-19) pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has made more than 125 million people infected and more than 2.7 million people dead globally. Airborne transmission has been recognized as one of the major transmission routes for SARS-CoV-2. This paper presents a systematic approach for evaluating the effectiveness of multi-scale IAQ control strategies in mitigating the infection risk in different scenarios. The IAQ control strategies across multiple scales from a whole building to rooms, and to cubical and personal microenvironments and breathing zone, are introduced, including elevated outdoor airflow rates, high-efficiency filters, advanced air distribution strategies, standalone air cleaning technologies, personal ventilation and face masks. The effectiveness of these strategies for reducing the risk of COVID-19 infection are evaluated for specific indoor spaces, including long-term care facility, school and college, meat plant, retail stores, hospital, office, correctional facility, hotel, restaurant, casino and transportation spaces like airplane, cruise ship, subway, bus and taxi, where airborne transmission are more likely to occur due to high occupancy densities. The baseline cases of these spaces are established according to the existing standards, guidelines or practices. Several integrated mitigation strategies are recommended and classified based on their relative cost and effort of implementation for each indoor space. They can be applied to help meet the current challenge of ongoing COVID-19, and provide better preparation for other possible epidemics and pandemics of airborne infectious diseases in the future.
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Affiliation(s)
- Jialei Shen
- Department of Mechanical and Aerospace Engineering, Syracuse University, 263 Link Hall, Syracuse, NY, 13244, USA
| | - Meng Kong
- Department of Mechanical and Aerospace Engineering, Syracuse University, 263 Link Hall, Syracuse, NY, 13244, USA
| | - Bing Dong
- Department of Mechanical and Aerospace Engineering, Syracuse University, 263 Link Hall, Syracuse, NY, 13244, USA
| | | | - Jianshun Zhang
- Department of Mechanical and Aerospace Engineering, Syracuse University, 263 Link Hall, Syracuse, NY, 13244, USA
- School of Architecture and Urban Planning, Nanjing University, 22 Hankou Road, Nanjing, Jiangsu Province, 210093, China
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46
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Maggiolo D, Sasic S. Respiratory droplets interception in fibrous porous media. PHYSICS OF FLUIDS (WOODBURY, N.Y. : 1994) 2021; 33:083305. [PMID: 34471337 PMCID: PMC8404382 DOI: 10.1063/5.0060947] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Accepted: 07/17/2021] [Indexed: 05/14/2023]
Abstract
We investigate, by means of pore-scale lattice Boltzmann simulations, the mechanisms of interception of respiratory droplets within fibrous porous media composing face masks. We simulate the dynamics, coalescence, and collection of droplets of the size comparable with the fiber and pore size in typical fluid-dynamic conditions that represent common expiratory events. We discern the fibrous microstructure into three categories of pores: small, large, and medium-sized pores, where we find that within the latter, the incoming droplets tend to be more likely intercepted. The size of the medium-sized pores relative to the fiber size is placed between the droplet-to-fiber size ratio and a porosity-dependent microstructural parameter L ϵ * = ϵ / ( 1 - ϵ ) , with ϵ being the porosity. In larger pores, droplets collection is instead inhibited by the small pore-throat-to-fiber size ratio that characterizes the pore perimeter, limiting their access. The efficiency of the fibrous media in intercepting droplets without compromising breathability, for a given droplet-to-fiber size ratio, can be estimated by knowing the parameter L ϵ * . We propose a simple model that predicts the average penetration of droplets into the fibrous media, showing a sublinear growth with L ϵ * . Permeability is shown also to scale well with L ϵ * but following a superlinear growth, which indicates the possibility of increasing the medium permeability at a little cost in terms of interception efficiency for high values of porosity. As a general design guideline, the results also suggest that a fibrous layer thickness relative to the fiber size should exceed the value L ϵ * in order to ensure effective droplets filtration.
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47
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De-Leon H, Pederiva F. Statistical mechanics study of the introduction of a vaccine against COVID-19 disease. Phys Rev E 2021; 104:014132. [PMID: 34412259 DOI: 10.1103/physreve.104.014132] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Accepted: 06/23/2021] [Indexed: 12/11/2022]
Abstract
By the end of 2020, a year since the first cases of infection by the Covid-19 virus have been reported; several pharmaceutical companies made significant progress in developing effective vaccines against the Covid-19 virus that has claimed the lives of more than 10^{6} people over the world. On the other hand, there is growing evidence of re-infection by the virus, which can cause further outbreaks. In this paper, we apply statistical physics tools to examine theoretically the vaccination rate required to control the pandemic for three different vaccine efficiency scenarios and five different vaccination rates. Also, we study the effect of temporal restrictions or reliefs on the pandemic's outbreak, assuming that re-infection is possible. When examining the efficiency of the vaccination rate of the general population in preventing an additional outbreak of the disease, we find that a high vaccination rate (where 0.3% of the population is vaccinated daily, which is equivalent to ≈10^{6} vaccine doses in the United States daily) is required to gain control over the spread of the virus without further restrictions.
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Affiliation(s)
- Hilla De-Leon
- INFN-TIFPA Trento Institute of Fundamental Physics and Applications, Via Sommarive, 14, 38123 Povo, Trento, Italy
- European Centre for Theoretical Studies in Nuclear Physics and Related Areas (ECT*), Strada delle Tabarelle 286, I-38123 Villazzano, Trento, Italy
| | - Francesco Pederiva
- INFN-TIFPA Trento Institute of Fundamental Physics and Applications, Via Sommarive, 14, 38123 Povo, Trento, Italy
- Dipartimento di Fisica, University of Trento, via Sommarive 14, I-38123 Povo, Trento, Italy
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Crawford C, Vanoli E, Decorde B, Lancelot M, Duprat C, Josserand C, Jilesen J, Bouadma L, Timsit JF. Modeling of aerosol transmission of airborne pathogens in ICU rooms of COVID-19 patients with acute respiratory failure. Sci Rep 2021; 11:11778. [PMID: 34083700 PMCID: PMC8175584 DOI: 10.1038/s41598-021-91265-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Accepted: 05/11/2021] [Indexed: 01/06/2023] Open
Abstract
The COVID-19 pandemic has generated many concerns about cross-contamination risks, particularly in hospital settings and Intensive Care Units (ICU). Virus-laden aerosols produced by infected patients can propagate throughout ventilated rooms and put medical personnel entering them at risk. Experimental results found with a schlieren optical method have shown that the air flows generated by a cough and normal breathing were modified by the oxygenation technique used, especially when using High Flow Nasal Canulae, increasing the shedding of potentially infectious airborne particles. This study also uses a 3D Computational Fluid Dynamics model based on a Lattice Boltzmann Method to simulate the air flows as well as the movement of numerous airborne particles produced by a patient's cough within an ICU room under negative pressure. The effects of different mitigation scenarii on the amount of aerosols potentially containing SARS-CoV-2 that are extracted through the ventilation system are investigated. Numerical results indicate that adequate bed orientation and additional air treatment unit positioning can increase by 40% the number of particles extracted and decrease by 25% the amount of particles deposited on surfaces 45s after shedding. This approach could help lay the grounds for a more comprehensive way to tackle contamination risks in hospitals, as the model can be seen as a proof of concept and be adapted to any room configuration.
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Affiliation(s)
- Cyril Crawford
- Ecole Polytechnique, IP Paris, 91128, Palaiseau, France.
- Department of Civil and Environmental Engineering, Imperial College London, SW7 2AZ, London, UK.
| | | | - Baptiste Decorde
- Laboratoire d'Hydrodynamique (LadHyX), UMR 7646 CNRS-Ecole Polytechnique, IP Paris, 91128, Palaiseau, France
| | | | - Camille Duprat
- Laboratoire d'Hydrodynamique (LadHyX), UMR 7646 CNRS-Ecole Polytechnique, IP Paris, 91128, Palaiseau, France
| | - Christophe Josserand
- Laboratoire d'Hydrodynamique (LadHyX), UMR 7646 CNRS-Ecole Polytechnique, IP Paris, 91128, Palaiseau, France
| | | | - Lila Bouadma
- AP-HP, Bichat Claude Bernard Hospital, Medical and Infectious Diseases ICU (MI2), 75018, Paris, France
- Université de Paris, IAME, INSERM, 75018, Paris, France
| | - Jean-François Timsit
- AP-HP, Bichat Claude Bernard Hospital, Medical and Infectious Diseases ICU (MI2), 75018, Paris, France
- Université de Paris, IAME, INSERM, 75018, Paris, France
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49
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Ju JTJ, Boisvert LN, Zuo YY. Face masks against COVID-19: Standards, efficacy, testing and decontamination methods. Adv Colloid Interface Sci 2021; 292:102435. [PMID: 33971389 PMCID: PMC8084286 DOI: 10.1016/j.cis.2021.102435] [Citation(s) in RCA: 47] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2021] [Revised: 04/27/2021] [Accepted: 04/28/2021] [Indexed: 12/12/2022]
Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus responsible for the novel coronavirus disease 2019 (COVID-19), has caused a global pandemic on a scale not seen for over a century. Increasing evidence suggests that respiratory droplets and aerosols are likely the most common route of transmission for SARS-CoV-2. Since the virus can be spread by presymptomatic and asymptomatic individuals, universal face masking has been recommended as a straightforward and low-cost strategy to mitigate virus transmission. Numerous governments and public health agencies around the world have advocated for or mandated the wearing of masks in public settings, especially in situations where social distancing is not possible. However, the efficacy of wearing a mask remains controversial. This interdisciplinary review summarizes the current, state-of-the-art understanding of mask usage against COVID-19. It covers three main aspects of mask usage amid the pandemic: quality standards for various face masks and their fundamental filtration mechanisms, empirical methods for quantitatively determining mask integrity and particle filtration efficiency, and decontamination methods that allow for the reuse of traditionally disposable N95 and surgical masks. The focus is given to the fundamental physicochemical and engineering sciences behind each aspect covered in this review, providing novel insights into the current understanding of mask usage to curb COVID-19 spread.
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Affiliation(s)
- Jerry T J Ju
- Department of Mechanical Engineering, University of Hawaii at Manoa, Honolulu, HI 96822, United States
| | - Leah N Boisvert
- Department of Pediatrics, John A. Burns School of Medicine, University of Hawaii, Honolulu, HI 96826, United States
| | - Yi Y Zuo
- Department of Mechanical Engineering, University of Hawaii at Manoa, Honolulu, HI 96822, United States; Department of Pediatrics, John A. Burns School of Medicine, University of Hawaii, Honolulu, HI 96826, United States.
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50
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Liu K, Allahyari M, Salinas J, Zgheib N, Balachandar S. Investigation of theoretical scaling laws using large eddy simulations for airborne spreading of viral contagion from sneezing and coughing. PHYSICS OF FLUIDS (WOODBURY, N.Y. : 1994) 2021; 33:063318. [PMID: 34335006 PMCID: PMC8320469 DOI: 10.1063/5.0054651] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Accepted: 05/11/2021] [Indexed: 05/19/2023]
Abstract
Using a set of large eddy point-particle simulations, we explore the fluid dynamics of an ejected puff resulting from a cough/sneeze. The ejection contains over 61 000 potentially virus-laden droplets at an injection Reynolds number of about 46 000, comparable to an actual cough/sneeze. We observe that global puff properties, such as centroid, puff volume, momentum, and buoyancy vary little across realizations. Other properties, such as maximum extent, shape, and edge velocity of the puff, may exhibit substantial variation. In many realizations, a portion of the puff splits off and advances along a random direction, while keeping airborne droplet nuclei afloat. This peeled-off portion provides a mechanism for virus-laden droplets to travel over large distances in a short amount of time. We also observe that the vast majority of droplets remain suspended within the puff after all liquid has evaporated. The main objectives of the study are to (i) evaluate assumptions of Balachandar's et al. theory [Int. J. Multiphase Flow 132, 103439 (2020)], which include buoyancy effects, shape of the puff, and droplet evaporation rate, (ii) obtain values of closure parameters, which include location and time of the virtual origin, and puff entrainment and drag coefficients, and (iii) evaluate the accuracy of the theory in predicting the shape, size, and location of the puff, as well as droplet number density long after ejection. The theory adequately predicts global puff properties including size, velocity, and distance traveled, the largest size of droplets that exit the puff due to settling, and the droplet size distribution within the puff long after ejection.
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Affiliation(s)
- K. Liu
- Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida 32611, USA
| | - M. Allahyari
- Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida 32611, USA
| | - J. Salinas
- Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida 32611, USA
| | - N. Zgheib
- Author to whom correspondence should be addressed:
| | - S. Balachandar
- Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida 32611, USA
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