Wildfire smoke likely increased risk of Covid in Nevada, study finds

In 2020, California endured the worst fire season in its history as three of the four largest fires ever recorded burned through the state.

Now researchers are learning how those fires may have contributed to the ongoing Covid-19 pandemic in Nevada.

New research published in the Journal of Exposure Science and Environmental Epidemiology suggests  long-term exposure to wildfire smoke may make the virus particularly deadly.

The research team, led by the Center for Genomic Medicine at the Desert Research Institute (DRI), analyzed the relationship between fine particles called PM2.5 found in air pollution and Covid-19 test positivity data from Renown Health, a health provider serving Northern Nevada, Lake Tahoe, and northeast California.

The increase of PM 2.5 from wildfire smoke was responsible for a nearly 18% increase in the number of Covid-19 cases that occurred during a period of prolonged smoke that took place between Aug. 16 and Oct. 10, 2020, according to the study.

The City of Reno was exposed to higher concentrations of the PM2.5 particulate for longer periods of time in 2020 than other nearby metropolitan areas, including San Francisco, said researchers.

“Our results showed a substantial increase in the COVID-19 positivity rate in Reno during a time when we were affected by heavy wildfire smoke from California wildfires,” said Daniel Kiser, co-lead author of the study and assistant research scientist of data science at DRI. “This is important to be aware of as we are already confronting heavy wildfire smoke from the Beckwourth Complex fire and with COVID-19 cases again rising in Nevada and other parts of the Western U.S.”

There is a growing consensus among researchers that air pollution, specifically PM2.5, exacerbates respiratory illness such as pneumonia and acute bronchitis by impairing the immune response.

Researchers at Harvard University’s T.H. Chan School of Public Health found similar results in a study of county-level data that suggested that even a small increase in the long term exposure of PM2.5 was associated with a 11% increase in the COVID-19 mortality rate.

The new research by DRI controlled for additional variables such as the general prevalence of the virus, air temperature, and the number of tests administered, in an area that was heavily impacted by wildfire smoke, building on previous studies in San Francisco and Orange County. 

“We believe that our study greatly strengthens the evidence that wildfire smoke can enhance the spread of SARS-CoV-2,” said Gai Elhanan, co-lead author of the study and associate research scientist of computer science at DRI. “We would love public health officials across the U.S. to be a lot more aware of this because there are things we can do in terms of public preparedness in the community to allow people to escape smoke during wildfire events.”