Wildfire smoke linked to 19,000 additional Covid cases in US West and 700 deaths

‘It’s a horrible combination – together, the wildfires and Covid-19 make us even sicker’

Wildfire smoke is linked to at least 19,000 additional cases of Covid-19 on the West Coast, and 700 subsequent deaths, a study has revealed.

The paper, published on Friday in the journal Science Advances, explores how last year’s unprecedented wildfire season worsened the impacts of the pandemic.

The research tracks increased infections during times of heavy smoke in 50 counties on the West Coast - California, Oregon, and Washington.

The biggest increases in infections related to wildfire smoke were found in the Sierra Nevada foothills and Central Valley in California. The Bay area also experienced spikes.

From March to December 2020, 1,754 cases were linked to wildfire smoke in Sonoma County, north of San Francisco, making up 13.1 per cent of total cases in the state.

The county with the highest share of cases related to wildfire smoke was Butte County with 17.3 per cent.

More than half of the 22 Covid deaths in Calaveras County were associated with smoke. Fresno saw 131 deaths caused by smoke-linked Covid-19 infections, and Alameda had 110 people.

These areas battled massive wildfires in 2020, exacerbated by the climate crisis.

The study’s authors say the correlation between smoke and Covid-19 is not a coincidence. Since the start of the pandemic, several studies have found that exposure to wildfire smoke makes you more susceptible to Covid-19.

Some scientists also think it’s possible that smoke particles could carry the virus.

The 2021 fire season is shaping up to be another disastrous period for western states, while the highly transmissible Delta variant continues to sweep across parts of the US.

“It’s a horrible combination,” researcher Francesca Dominici told the San Francisco Chronicle. “Together, the wildfires and Covid-19 make us even sicker.”

The researchers compared Covid data from 92 counties during periods of clear skies, compared when wildfire smoke permeated the air.

Areas closest to wildfires last year were found to have the strongest link between smoke and Covid-19.

Mendocino County suffered the August Complex, the largest wildfire in the state’s history. Some 14.6 per cent of Covid-19 cases in the county were linked to wildfire smoke.

Sacramento County had the highest number of smoke-linked Covid cases at 4,639.

Factors which made areas more likely to have high numbers of Covid-19 cases also made them vulnerable to wildfire smoke, the researchers said. These included the county’s demographic make-up along with the number of residents with pre-existing medical conditions and access to healthcare.

The study noted that in several counties, like San Francisco, the precautions that people took against Covid-19 - such as staying at home, buying air filters and wearing masks outdoors - also protected them against wildfires.

During the 2020 wildfire season in California, 4.1 million acres burned.

“This study is just one more set of evidence that we have to be doubling down on our efforts to reduce catastrophic wildfire risk,” professor of medicine at the University of California, John Balmes, told theChronicle.