Identifying airborne transmission as the dominant route for the spread of COVID-19
- aDepartment of Atmospheric Sciences, Texas A&M University, College Station, TX 77843;
- bDepartment of Chemistry, Texas A&M University, College Station, TX 77843;
- cDepartment of Chemistry, College of Natural Sciences, The University of Texas at Austin, Austin, TX 78712;
- dDivision of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125;
- eDepartment of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA 92093
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Contributed by Mario J. Molina, May 16, 2020 (sent for review May 14, 2020; reviewed by Manish Shrivastava and Tong Zhu)

Significance
We have elucidated the transmission pathways of coronavirus disease 2019 (COVID-19) by analyzing the trend and mitigation measures in the three epicenters. Our results show that the airborne transmission route is highly virulent and dominant for the spread of COVID-19. The mitigation measures are discernable from the trends of the pandemic. Our analysis reveals that the difference with and without mandated face covering represents the determinant in shaping the trends of the pandemic. This protective measure significantly reduces the number of infections. Other mitigation measures, such as social distancing implemented in the United States, are insufficient by themselves in protecting the public. Our work also highlights the necessity that sound science is essential in decision-making for the current and future public health pandemics.
Abstract
Various mitigation measures have been implemented to fight the coronavirus disease 2019 (COVID-19) pandemic, including widely adopted social distancing and mandated face covering. However, assessing the effectiveness of those intervention practices hinges on the understanding of virus transmission, which remains uncertain. Here we show that airborne transmission is highly virulent and represents the dominant route to spread the disease. By analyzing the trend and mitigation measures in Wuhan, China, Italy, and New York City, from January 23 to May 9, 2020, we illustrate that the impacts of mitigation measures are discernable from the trends of the pandemic. Our analysis reveals that the difference with and without mandated face covering represents the determinant in shaping the pandemic trends in the three epicenters. This protective measure alone significantly reduced the number of infections, that is, by over 75,000 in Italy from April 6 to May 9 and over 66,000 in New York City from April 17 to May 9. Other mitigation measures, such as social distancing implemented in the United States, are insufficient by themselves in protecting the public. We conclude that wearing of face masks in public corresponds to the most effective means to prevent interhuman transmission, and this inexpensive practice, in conjunction with simultaneous social distancing, quarantine, and contact tracing, represents the most likely fighting opportunity to stop the COVID-19 pandemic. Our work also highlights the fact that sound science is essential in decision-making for the current and future public health pandemics.
Footnotes
- ↵1To whom correspondence may be addressed. Email: renyi-zhang{at}tamu.edu or mjmolina{at}ucsd.edu.
Author contributions: R.Z. designed research; R.Z., Y.L., and Y.W. performed research; R.Z., Y.L., Y.W., and M.J.M. analyzed data; and R.Z., A.L.Z., and M.J.M. wrote the paper.
Reviewers: M.S., Pacific Northwest National Laboratory; and T.Z., Peking University.
The authors declare no competing interest.
This article contains supporting information online at https://www.pnas.org/lookup/suppl/doi:10.1073/pnas.2009637117/-/DCSupplemental.
- Copyright © 2020 the Author(s). Published by PNAS.
This open access article is distributed under Creative Commons Attribution License 4.0 (CC BY).
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