The flow physics of COVID-19
TL;DR: In this article, the authors summarized what we know and what we need to learn about the science underlying these issues so that we are better prepared to tackle the next outbreak of COVID-19 or a similar disease.
Abstract: Flow physics plays a key role in nearly every facet of the COVID-19 pandemic. This includes the generation and aerosolization of virus-laden respiratory droplets from a host, its airborne dispersion and deposition on surfaces, as well as the subsequent inhalation of these bioaerosols by unsuspecting recipients. Fluid dynamics is also key to preventative measures such as the use of face masks, hand washing, ventilation of indoor environments and even social distancing. This article summarizes what we know and, more importantly, what we need to learn about the science underlying these issues so that we are better prepared to tackle the next outbreak of COVID-19 or a similar disease.
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TL;DR: For society to resume, measures designed to reduce aerosol transmission must be implemented, including universal masking and regular, widespread testing to identify and isolate infected asymptomatic individuals.
Abstract: Masks and testing are necessary to combat asymptomatic spread in aerosols and droplets Respiratory infections occur through the transmission of virus-containing droplets (>5 to 10 µm) and aerosols (≤5 µm) exhaled from infected individuals during breathing, speaking, coughing, and sneezing. Traditional respiratory disease control measures are designed to reduce transmission by droplets produced in the sneezes and coughs of infected individuals. However, a large proportion of the spread of coronavirus disease 2019 (COVID-19) appears to be occurring through airborne transmission of aerosols produced by asymptomatic individuals during breathing and speaking (1—3). Aerosols can accumulate, remain infectious in indoor air for hours, and be easily inhaled deep into the lungs. For society to resume, measures designed to reduce aerosol transmission must be implemented, including universal masking and regular, widespread testing to identify and isolate infected asymptomatic individuals.
689 citations
TL;DR: In this article, the authors discuss current evidence regarding the transmission of respiratory viruses by aerosols-how they are generated, transported, and deposited, as well as the factors affecting the relative contributions of droplet-spray deposition versus aerosol inhalation as modes of transmission.
Abstract: The COVID-19 pandemic has revealed critical knowledge gaps in our understanding of and a need to update the traditional view of transmission pathways for respiratory viruses. The long-standing definitions of droplet and airborne transmission do not account for the mechanisms by which virus-laden respiratory droplets and aerosols travel through the air and lead to infection. In this Review, we discuss current evidence regarding the transmission of respiratory viruses by aerosols-how they are generated, transported, and deposited, as well as the factors affecting the relative contributions of droplet-spray deposition versus aerosol inhalation as modes of transmission. Improved understanding of aerosol transmission brought about by studies of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection requires a reevaluation of the major transmission pathways for other respiratory viruses, which will allow better-informed controls to reduce airborne transmission.
492 citations
TL;DR: Research findings on the physics of aerosol and droplet dispersion relevant to the hypothesized aerosol transmission of SARS-CoV-2 during the current pandemic are provided.
324 citations
TL;DR: The role of building ventilation on the possible pathways of airborne particles and the fluid mechanics of the processes involved in indoor transmission of SARS-CoV-2 are discussed.
Abstract: Although the relative importance of airborne transmission of the SARS-CoV-2 virus is controversial, increasing evidence suggests that understanding airflows is important for estimation of the risk of contracting COVID-19. The data available so far indicate that indoor transmission of the virus far outstrips outdoor transmission, possibly due to longer exposure times and the decreased turbulence levels (and therefore dispersion) found indoors. In this paper we discuss the role of building ventilation on the possible pathways of airborne particles and examine the fluid mechanics of the processes involved.
271 citations
TL;DR: In this paper, the authors derived an indoor safety guideline that would impose an upper bound on the cumulative exposure time, the product of the number of occupants and their time in an enclosed space, and demonstrate how this bound depends on the rates of ventilation and air filtration, dimensions of the room, breathing rate, respiratory activity and face mask use of its occupants.
Abstract: The current revival of the American economy is being predicated on social distancing, specifically the Six-Foot Rule, a guideline that offers little protection from pathogen-bearing aerosol droplets sufficiently small to be continuously mixed through an indoor space. The importance of airborne transmission of COVID-19 is now widely recognized. While tools for risk assessment have recently been developed, no safety guideline has been proposed to protect against it. We here build on models of airborne disease transmission in order to derive an indoor safety guideline that would impose an upper bound on the "cumulative exposure time," the product of the number of occupants and their time in an enclosed space. We demonstrate how this bound depends on the rates of ventilation and air filtration, dimensions of the room, breathing rate, respiratory activity and face mask use of its occupants, and infectiousness of the respiratory aerosols. By synthesizing available data from the best-characterized indoor spreading events with respiratory drop size distributions, we estimate an infectious dose on the order of 10 aerosol-borne virions. The new virus (severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2]) is thus inferred to be an order of magnitude more infectious than its forerunner (SARS-CoV), consistent with the pandemic status achieved by COVID-19. Case studies are presented for classrooms and nursing homes, and a spreadsheet and online app are provided to facilitate use of our guideline. Implications for contact tracing and quarantining are considered, and appropriate caveats enumerated. Particular consideration is given to respiratory jets, which may substantially elevate risk when face masks are not worn.
245 citations
References
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TL;DR: Aerosol and Surface Stability of SARS-CoV-2 In this research letter, investigators report on the stability of Sars-CoVs and the viability of the two virus under experimental conditions.
Abstract: Aerosol and Surface Stability of SARS-CoV-2 In this research letter, investigators report on the stability of SARS-CoV-2 and SARS-CoV-1 under experimental conditions. The viability of the two virus...
7,412 citations
Book•
27 Jul 1982
TL;DR: Properties of Gases Uniform Particle Motion Particle size Statistics Straight-Line Acceleration and Curvilinear Particle motion Adhesion of Particles Brownian Motion and Diffusion Thermal and Radiometric Forces Filtration Sampling and Measurement of Concentration Respiratory Deposition Coagulation Condensation and Evaporation Atmospheric Aerosols Electrical Properties Optical Properties Bulk Motion of aerosols Dust Explosions Bioaerosols Microscopic measurement of Particle Size Production of Test aerosols Appendices Index Index
Abstract: Properties of Gases Uniform Particle Motion Particle Size Statistics Straight-Line Acceleration and Curvilinear Particle Motion Adhesion of Particles Brownian Motion and Diffusion Thermal and Radiometric Forces Filtration Sampling and Measurement of Concentration Respiratory Deposition Coagulation Condensation and Evaporation Atmospheric Aerosols Electrical Properties Optical Properties Bulk Motion of Aerosols Dust Explosions Bioaerosols Microscopic Measurement of Particle Size Production of Test Aerosols Appendices Index
5,208 citations
TL;DR: Results of an analysis of nasal and throat swabs from 17 patients in Zhuhai, China, who had received a diagnosis of Covid-19 and found SARS-CoV-2 Viral Load in Upper Respiratory Specimens positive.
Abstract: SARS-CoV-2 Viral Load in Upper Respiratory Specimens The authors report results of an analysis of nasal and throat swabs from 17 patients in Zhuhai, China, who had received a diagnosis of Covid-19....
4,236 citations
TL;DR: This study describes possible transmission of novel coronavirus disease 2019 (COVID-19) from an asymptomatic Wuhan resident to 5 family members in Anyang, a Chinese city in the neighboring province of Hubei.
Abstract: This study describes possible transmission of novel coronavirus disease 2019 (COVID-19) from an asymptomatic Wuhan resident to 5 family members in Anyang, a Chinese city in the neighboring province of Hubei.
3,818 citations
Book•
01 Jan 1999
TL;DR: Aerosol Technology, Second Edition as mentioned in this paper is the #1 guide to aerosol science and technology and has been the text of choice among students and professionals who need to acquire a thorough working knowledge of modern aerosol theory and applications.
Abstract: The #1 guide to aerosol science and technology -now better than everSince 1982, Aerosol Technology has been the text of choice among students and professionals who need to acquire a thorough working knowledge of modern aerosol theory and applications. Now revised to reflect the considerable advances that have been made over the past seventeen years across a broad spectrum of aerosol-related application areas - from occupational hygiene and biomedical technology to microelectronics and pollution control -this new edition includes:* A chapter on bioaerosols* New sections on resuspension, transport losses, respiratory deposition models, and fractal characterization of particles* Expanded coverage of atmospheric aerosols, including background aerosols and urban aerosols* A section on the impact of aerosols on global warming and ozone depletion.Aerosol Technology, Second Edition also features dozens of new, fully worked examples drawn from a wide range of industrial and research settings, plus new chapter-end practice problems to help readers master the material quickly.
3,237 citations