As record-breaking wildfires rage across the western U.S., environmental and public health professionals are assessing its impacts on COVID-19 symptoms, spread, and safety precautions.

Causing 6.5 million deaths every year, air pollution is the world’s fourth-largest threat to human health. Wildfire smoke contains pollutants that cause lung inflammation, compromised immune function and increased susceptibility to respiratory infections—like COVID-19.

Cloth face coverings used to slow the spread of coronavirus offer only minimal protection against pollutants in wildfire smoke (they don’t capture the smallest particles). And recent research offers a clear link between long-term exposure to pollution and COVID-19 mortality.

Amid the raging fires, tens of thousands have been forced to evacuate their homes across California, Oregon and Washington. But because COVID-19 is airborne and easily spread in close quarters, shelters pose great risks as well.

“The last thing we want to have happen is people to remain in the path of a wildfire…because they think it’s safer to do that than risk a shelter,” said Brad Kieserman, vice president of disaster operations and logistics for the American Red Cross.

Firefighters are in a particularly tough position. Typical working conditions make social distancing and hand washing difficult, enabling the virus to spread quickly in fire camps. But if firefighters are quarantined, they are not available for emergency calls.  

As wildfire and pandemic conditions continue to change rapidly, the full fallout of the disasters remains to be seen.

Said Clackamas County, Oregon health officer, Sarah Present: “This is a once-in-a-lifetime smoke event in the middle of a once-in-a-lifetime pandemic. I’ve never seen a public health situation like this.”