As the world warms, disasters collide. That’s happening right now, as health experts warn that exposure to wildfire smoke across North America increases the risks of catching COVID-19 and worsens the impacts for people who already have or are particularly susceptible to the virus.

"Exposure to air pollution from wildfire smoke can increase susceptibility to COVID and other respiratory diseases,” says Kristie Ebi, a climate and health professor at the University of Washington.

Here’s how it works: Wildfire smoke contains very small particles called PM 2.5, which can get inhaled and stuck in the body, causing irritation and ultimately affecting the immune system. These particles can "make you more prone to lung infections, including SARS-CoV-2, the virus that causes COVID-19,” warns the Centers for Disease Control and Prevention on its Wildfire Smoke and COVID-19 webpage.