Biological fluid dynamics of airborne COVID-19 infection
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REVIEW
Biological fluid dynamics of airborne COVID‑19 infection Giovanni Seminara1,2 · Bruno Carli1,3 · Guido Forni1 · Sandro Fuzzi4 · Andrea Mazzino5,6 · Andrea Rinaldo1,7,8 Received: 30 June 2020 / Accepted: 21 July 2020 / Published online: 16 August 2020 © The Author(s) 2020
Abstract We review the state of knowledge on the bio-fluid dynamic mechanisms involved in the transmission of the infection from SARS-CoV-2. The relevance of the subject stems from the key role of airborne virus transmission by viral particles released by an infected person via coughing, sneezing, speaking or simply breathing. Speech droplets generated by asymptomatic disease carriers are also considered for their viral load and potential for infection. Proper understanding of the mechanics of the complex processes whereby the two-phase flow emitted by an infected individual disperses into the environment would allow us to infer from first principles the practical rules to be imposed on social distancing and on the use of facial and eye protection, which to date have been adopted on a rather empirical basis. These measures need compelling scientific validation. A deeper understanding of the relevant biological fluid dynamics would also allow us to evaluate the contrasting effects of natural or forced ventilation of environments on the transmission of contagion: the risk decreases as the viral load is diluted by mixing effects but contagion is potentially allowed to reach larger distances from the infected source. To that end, our survey supports the view that a formal assessment of a number of open problems is needed. They are outlined in the discussion. Graphic abstract
Keywords Respiratory emissions · Coughing, sneezing, speaking · Clouds, jets, puffs · Droplets · Distancing · Non-pharmaceutical protection measures Extended author information available on the last page of the article
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Whether generated by rotting matter or emanating from infected persons, animals, or objects, the venomous atoms would infect salubrious air and make it “miasmatic”—that is, poisonous. It was indeed the “corruption” of the air that, according to the doctors of the Renaissance, was the basic precondition for the outbreak of an epidemic of plague. Fighting the Plague in Seventeenth Century Italy, The University of Wisconsin Press, Madison 1981, p. 8. (Carlo Cipolla, 1922–2000, Linceo from 1987). (photo credit: National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health.)
1 Introduction In a report published by the US National Academy of Sciences (NAS) on the reuse of facemasks for the protection against respiratory viral infection, it is stated that: The public is likely to forgive lack of knowledge but will not be willing to trust public health officials in the next instance if they have in any way been misinformed or misled (National Academy of Sciences of the United States, 2006, p. 67) This statement poses an important question, that of information and citizens’ right to knowledge. Bearing
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