Aerosol transmission of SARS-CoV-2: physical principles and implications

Abstract

Evidence has recently emerged that SARS-CoV-2, the coronavirus that causes COVID-19, can be transmitted airborne in aerosol particles as well as in droplets of larger size or in surface deposits. This minireview outlines the underlying aerosol science, making links to meteorological aerosol research where some of the processes governing the size of aerosol and larger droplets are better understood. SARS-CoV-2 in aerosol form is emitted during normal breathing and speech by both asymptomatic and symptomatic people, remaining viable with a half-life of up to about an hour during which air movement can carry it considerable distances, although it simultaneously disperses. Evaporation reduces the size of the droplets, whereas coalescence increases the mean droplet size. Aerosol particles containing SARS-CoV-2 can also coalesce with pollution particulates, and pollution increases infection rates. The operation of ventilation systems in public buildings and transportation can create infection hazards via aerosols, but provides opportunities for reducing the risk of transmission in ways as simple as switching from recirculated to outside air. There are also opportunities to reduce the viability of SARS-CoV-2 in aerosol form with sunlight or UV lamps. The efficiency of masks for blocking aerosol transmission depends strongly on how well they fit. Research areas that urgently need further experimentation include the basis for variation in droplet size distribution, including droplets emitted by ‘superspreader’ individuals; the evolution of droplet sizes after emission and their dispersal by turbulence, which gives a different basis for social distancing.

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Identifiers

DOI

https://doi.org/10.3389/fpubh.2020.590041

Repository URI

http://eprints.gla.ac.uk/225905/