Beggs, C.B.; Abid, R.; Motallebi, F.; Samad, A.; Venkatesan, N.; Avital, E.J. Airborne Transmission of SARS-CoV-2: The Contrast between Indoors and Outdoors. Fluids2024, 9, 54.
Beggs, C.B.; Abid, R.; Motallebi, F.; Samad, A.; Venkatesan, N.; Avital, E.J. Airborne Transmission of SARS-CoV-2: The Contrast between Indoors and Outdoors. Fluids 2024, 9, 54.
Beggs, C.B.; Abid, R.; Motallebi, F.; Samad, A.; Venkatesan, N.; Avital, E.J. Airborne Transmission of SARS-CoV-2: The Contrast between Indoors and Outdoors. Fluids2024, 9, 54.
Beggs, C.B.; Abid, R.; Motallebi, F.; Samad, A.; Venkatesan, N.; Avital, E.J. Airborne Transmission of SARS-CoV-2: The Contrast between Indoors and Outdoors. Fluids 2024, 9, 54.
Abstract
Covid-19 is an airborne disease, with the vast majority of infections occurring indoors. By comparison, little transmission occurs outdoors. Here, we investigate the airborne transmission pathways that differentiate the indoors from outdoors, and conclude that profound differences exist, which help to explain why SARS-CoV-2 transmission is much more prevalent indoors. Near and far-field transmission pathways are discussed along with factors that affect infection risk, with aerosol concentration, air entrainment, thermal plumes, and occupancy duration all identified as being influential. In particular, we present the fundamental equations that underpin the Wells-Riley model, and show the mathematical relationship between inhaled virus particles and quanta of infection. A simple model is also presented for assessing infection risk in spaces with incomplete air mixing. Transmission risk is assessed in terms of aerosol concentration using simple 1D equations, followed by a description of thermal plume-ceiling interactions. With respect to this, we present new experimental results using Schlieren-visualisation and Computational Fluid Dynamics (CFD) based on the Eulerian-Lagrangian approach. Pathways of airborne infection are discussed, with the key differences identified between indoors and outdoors. In particular, the contribution of thermal and exhalation plumes is evaluated, and the presence of near-field/far-field feedback loop postulated, which is absent outdoors.
Keywords
SARS-CoV-2; aerosols; airborne transmission; infection risk; thermal plumes; ceilings; Wells-Riley; Schlieren; Computational Fluid Dynamics; near and far-field
Subject
Biology and Life Sciences, Virology
Copyright:
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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