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HomeCoronavirusAirborne transmission is dominant route for spread of COVID-19 — US analysis

Airborne transmission is dominant route for spread of COVID-19 — US analysis

A study by a team of researchers led by a Texas A&M University professor has found that not wearing a face mask dramatically increases a person's chances of being infected by the COVID-19 virus.

Dr Renyi Zhang, Texas A&M distinguished professor of atmospheric sciences and the Harold J Haynes chair in the College of Geosciences, and colleagues from the University of Texas, the University of California-San Diego and the California Institute of Technology examined the chances of COVID-19 infection and how the virus is easily passed from person to person. From trends and mitigation procedures in China, Italy and New York City, the researchers found that using a face mask reduced the number of infections by more than 78,000 in Italy from April 6-May 9 and by over 66,000 in New York City from 17 April-9 May.

"Our results clearly show that airborne transmission via respiratory aerosols represents the dominant route for the spread of COVID-19," Zhang said. "By analysing the pandemic trends without face-covering using the statistical method and by projecting the trend, we calculated that over 66,000 infections were prevented by using a face mask in little over a month in New York City. We conclude that wearing a face mask in public corresponds to the most effective means to prevent inter-human transmission.

"This inexpensive practice, in conjunction with social distancing and other procedures, is the most likely opportunity to stop the COVID-19 pandemic. Our work also highlights that sound science is essential in decision-making for the current and future public health pandemics."

One of the paper's co-authors, Mario Molina, is a professor at the University of California-San Diego and a co-recipient of the 1995 Nobel Prize in Chemistry for his role in understanding the threat to the Earth's ozone layer of human-made halocarbon gases.

"Our study establishes very clearly that using a face mask is not only useful to prevent infected coughing droplets from reaching uninfected persons, but is also crucial for these uninfected persons to avoid breathing the minute atmospheric particles (aerosols) that infected people emit when talking and that can remain in the atmosphere tens of minutes and can travel tens of feet," Molina said.

Zhang said that many people in China have worn face masks for years, mainly because of the bad air quality of the country. "So people there are sort of used to this," he said. "Mandated face-covering helped China in containing the COVID-19 outbreak."

Zhang said the results should send a clear message to people worldwide – wearing a face mask is essential in fighting the virus.

"Our work suggests that the failure in containing the propagation of COVID-19 pandemic worldwide is largely attributed to the unrecognised importance of airborne virus transmission," he said. "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."

The study was funded by the Robert A Welch Foundation.

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 78,000 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.

Authors
Renyi Zhang, Yixin Li, Annie L Zhang, Yuan Wang, Mario J Molina

[link url="https://www.sciencedaily.com/releases/2020/06/200612172200.htm"]Texas A&M University material[/link]

 

[link url="https://www.pnas.org/content/early/2020/06/10/2009637117"]Proceedings of the National Academy of Sciences abstract[/link]

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