publication . Article . Preprint . 2021

Evolution of spray and aerosol from respiratory releases: theoretical estimates for insight on viral transmission

P. M. de Oliveira; L. C. C. Mesquita; Savvas Gkantonas; Andrea Giusti; Epaminondas Mastorakos;
Open Access English
  • Published: 20 Jan 2021 Journal: Proceedings. Mathematical, Physical, and Engineering Sciences, volume 477, issue 2,245 (issn: 1364-5021, eissn: 1471-2946, Copyright policy)
  • Publisher: The Royal Society Publishing
  • Country: United Kingdom
By modelling the evaporation and settling of droplets emitted during respiratory releases and using previous measurements of droplet size distributions and SARS-CoV-2 viral load, estimates of the evolution of the liquid mass and the number of viral copies suspended were performed as a function of time from the release. The settling times of a droplet cloud and its suspended viral dose are significantly affected by the droplet composition. The aerosol (defined as droplets smaller than 5 μ m) resulting from 30 s of continued speech has O(1 h) settling time and a viable viral dose an order-of-magnitude higher than in a short cough. The time-of-flight to reach 2 m is only a few seconds resulting in a viral dose above the minimum required for infection, implying that physical distancing in the absence of ventilation is not sufficient to provide safety for long exposure times. The suspended aerosol emitted by continuous speaking for 1 h in a poorly ventilated room gives 0.1–11% infection risk for initial viral loads of 10 8 – 10 10   copies ml l − l , respectively, decreasing to 0.03–3% for 10 air changes per hour by ventilation. The present results provide quantitative estimates useful for the development of physical distancing and ventilation controls.
Fields of Science and Technology classification (FOS)
01 natural sciences, 0103 physical sciences, 010305 fluids & plasmas, 03 medical and health sciences, 0302 clinical medicine, 030212 general & internal medicine
free text keywords: 1006, 26, 1009, 73, Research Article, respiratory releases, viral transmission, COVID-19, General Physics and Astronomy, General Engineering, General Mathematics, 01 Mathematical Sciences, 02 Physical Sciences, 09 Engineering, Environmental science, Air changes per hour, Respiratory system, Atmospheric sciences, Evaporation, Aerosol, Settling, Viral load, Settling time, Ventilation (architecture), law.invention, law, Droplet size, Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), Viral transmission
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