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Edited by Peter B. Moore, Yale University, New Haven, CT, and approved August 15, 2020 (received for review June 11, 2020)
Abstract
To make the physics of person-to-person virus transmission from emitted droplets of oral fluid while speaking easily understood, we present simple and transparent algebraic equations that capture the essential physics of the problem. Calculations with these equations provide a straightforward way of determining whether emitted droplets remain airborne or rapidly fall to the ground, after accounting for the decrease in droplet size from water evaporation. At a relative humidity of 50%, for example, droplets with initial radii larger than about 50 μm rapidly fall to the ground, while smaller, potentially virus-containing droplets shrink in size from water evaporation and remain airborne for many minutes. Estimates of airborne virion emission rates while speaking strongly support the proposal that mouth coverings can help contain the COVID-19 pandemic.
Footnotes
- ↵1To whom correspondence may be addressed. Email: rnetz{at}physik.fu-berlin.de or eaton{at}nih.gov.
Author contributions: R.R.N. and W.A.E. designed research, performed research, analyzed data, and wrote the paper.
The authors declare no competing interest.
Data Availability.
All study data are included in the article.
- Copyright © 2020 the Author(s). Published by PNAS.
This open access article is distributed under Creative Commons Attribution License 4.0 (CC BY).
Physics of virus transmission by speaking droplets
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