Face Coverings Are Key to Thwarting the Spread of COVID-19

Study: Airborne transmission is the most dominant route for spreading COVID-19.

Posted Jun 12, 2020

A new study identifies airborne transmission via respiratory aerosols as a highly virulent and dominant route for the spread of coronavirus disease 2019 (COVID-19). Based on these findings, the authors state: "Our analysis reveals that the difference with and without mandated face covering represents the determinant in shaping the trends of the pandemic worldwide."

This paper (Zhang et al., 2020) by a team of researchers led by a Texas A&M University professor of atmospheric sciences, Renyi Zhang, reports that wearing a face mask in public significantly decreases someone's risk of being infected with the COVID-19 (SARS-CoV-2) virus. These findings were published on June 11 in the journal Proceedings of the National Academy of Sciences.

"Our results clearly show that airborne transmission via respiratory aerosols represents the dominant route for the spread of COVID-19," Zhang said in a news release. "The results should send a clear message to people worldwide—wearing a face mask is essential in fighting the virus." 

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In addition to self-isolation, social distancing, and frequent hand washing, the researchers conclude that wearing face masks in public also helps to thwart the interhuman transmission of the SARS-CoV-2 virus.

"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, prior to the development of a vaccine," the authors state. 

This study suggests that wearing face masks in public can help to prevent large droplets and small aerosols from an infected person reaching the human respiratory tract of others. "Human atomization of virus-bearing particles occurs from coughing/sneezing and even from normal breathing/talking by an infected person," the authors explain.

Face coverings also reduce the odds of uninfected people inhaling tiny atmospheric particles that contain the virus when an infected person near them is breathing or talking. When someone inhales virus-bearing aerosols, the SARS-CoV-2 virus deposits directly along the human respiratory tract. "The enormous scope and magnitude of the COVID-19 outbreak reflect not only a highly contagious nature but also exceedingly efficient transmission for SARS-CoV-2," the authors write. 

"Minute atmospheric particles (aerosols) that infected people emit when talking can remain in the atmosphere tens of minutes and can travel tens of feet," senior author Mario Molina said in the news release. Molina is a professor at the University of California, San Diego (UCSD) and a co-recipient of a Nobel Prize in Chemistry (1995) for his "work in atmospheric chemistry, particularly concerning the formation and decomposition of ozone."

"Our work suggests that the failure in containing the propagation of COVID-19 pandemic worldwide is largely attributed to the unrecognized importance of airborne virus transmission," Zhang concluded. "Social-distancing and washing our hands must continue, but that's not sufficient enough protection. Wearing a face mask as well as practicing good hand hygiene and social distancing will greatly reduce the chances of anyone contracting the COVID-19 virus."

UPDATE (June 30, 2020): This study (Zhang et al., 2020) has become controversial. On June 18, a group of scientists filed a formal request with the editorial board at the Proceedings of the National Academy of Sciences to have this study retracted. The uproar isn't so much about whether or not face masks help to thwart the spread of SARS-CoV-2 (they do); the scientists asking for a retraction took issue the study's underlying methodology and expressed other concerns. Renyi Zhang and Mario Molina issued a response letter defending their study


Renyi Zhang, Yixin Li, Annie L. Zhang, Yuan Wang, and Mario J. Molina. "Identifying Airborne Transmission as the Dominant Route for the Spread of COVID-19." PNAS (First published: June 11, 2020) DOI: 10.1073/pnas.2009637117