New study shows a 17.7 percent increase in COVID-19 cases after a prolonged forest fire smoke event in 2020 in Reno, New York.

Credit: U.S. Department of Agriculture

Reno, Nevada (July 15, 2021) – Wildfire smoke can greatly increase susceptibility to SARS-CoV-2, the virus that causes COVID-19, according to a new study from the Center for Genomic Medicine at the Desert Research Institute (DRI), Washoe County Health District (WCHD) and Renown Health (Renown) in Reno, New York.

In a study earlier this week in the Journal of Exposure Science and Environmental Epidemiology, the DRI-led research team set out to investigate whether smoke from forest fires in the western United States in 2020 was linked to an increase in SARS-CoV-2 infections in Reno.

To investigate this, the study team used models to analyze the relationship between particulate matter (PM 2.5) from forest fire smoke and SARS-CoV-2 test positivity rate data from Renown Health, a large, integrated health network for Nevada, Lake Tahoe . and Northeast California.

According to their findings, PM 2.5 from forest fire smoke was responsible for a 17.7 percent increase in the number of COVID-19 cases that occurred during an extended smoking period between August 16 and October 10, 2020.

“Our results showed a significant increase in the COVID-19 positivity rate in Reno during a time we were exposed to heavy forest fire smoke from California forest fires,” said Daniel Kiser, MS, study co-lead author and data science research fellow at DRI . “This is important to note as we have already faced heavy wildfire smoke from the Beckwourth Complex fire and COVID-19 cases are increasing again in Nevada and other parts of the western US.”

Reno, located in Washoe County (population 450,000) in northern Nevada, was exposed to higher levels of PM2.5 for longer periods in 2020 than other nearby metropolitan areas, including San Francisco. Reno experienced 43 days of increased PM2.5 during the study period, as opposed to 26 days in the San Francisco Bay Area.

“We had a unique situation here in Reno last year where we were exposed to more wildfire smoke than in many other areas, including the Bay Area,” said Gai Elhanan, MD, co-lead author of the study and associate research scientist on computer science DRI. “We are in a valley between the mountains that limits the spread of pollutants and potentially increases exposure, making it even more important for us to understand the effects of smoke on human health.”

The new research by Kiser and Elhanan builds on previous studies in San Francisco and Orange Counties by controlling additional variables such as the general prevalence of the virus, air temperature, and the number of tests performed in a location badly affected by wildfire smoke .

“We believe our study strengthens the evidence that forest fire smoke can promote the spread of SARS-CoV-2,” Elhanan said. “We’d love to see US health officials become much more aware of this because there are things we can do about community public readiness to help people escape the smoke in forest fires.”


More information:

Other study authors are William Metcalf (DRI), Brendan Schnieder (WCHD) and Joseph Grzymski, a corresponding author (DRI / Renown).

This research was funded by Renown Health and the Governor of Nevada’s Coronavirus Relief Fund, the Office of Economic Development.

The full text of the study “SARS-CoV-2 Test Positive Rate in Reno, Nevada: Association with PM2.5 During the 2020 Wildfire Smoke Events in the Western United States” is available from the Journal of Exposure Science and Environmental Epidemiology: https: // /Items/s41370-021-00366-w

About DRI

The Desert Research Institute (DRI) is a recognized world market leader in basic and applied environmental research. Committed to scientific excellence and integrity, DRI faculties, students who work with them, and staff have developed scientific knowledge and innovative technologies in research projects around the world. Since 1959, the DRI’s research has expanded scientific knowledge on topics ranging from the effects of humans on the environment to the effects of the environment on humans. DRI’s powerful science and inspirational solutions support Nevada’s diverse economy, provide science-based education, and educate policy makers, business leaders, and community members. With locations in Las Vegas and Reno, DRI serves as the nonprofit research arm of the Nevada System of Higher Education. Further information is available at http: //

About Renomme Health

Renown Health is the area’s largest local nonprofit integrated health network serving Nevada, Lake Tahoe, and northeast California. With a diverse workforce of more than 7,000 employees, Renown has fostered a longstanding culture of excellence, determination and innovation. The organization includes a trauma center, two acute care hospitals, a children’s hospital, a rehabilitation clinic, a group of doctors and an emergency care network, as well as the largest non-profit insurance company in the region, Hometown Health. Renowned is currently enrolling in the world’s largest community-based genetic population health study, the Healthy Nevada Project®. More information is available at

Via the Air Quality Management Department in Washoe County’s Health District

The Air Quality Management Division (AQMD) implements clean air solutions that protect the quality of life for citizens of Reno, Sparks, and Washoe Counties through community partnerships, programs and services such as air surveillance, approval and compliance, planning, and public education. To learn more, please visit

https: // /Forest fire-smoke-exposure-associated-with-increased-risk-of-infection-covid-19 /


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