17 to 18 percent of COVID-19 cases in Butte County, CA and Whitman County, WA, from March 15, 2020 to December 16, 2020, were associated with wildfire smoke, according to a recent study.
Harvard University researchers estimated that exposure to particulate matter in smoke which measures 2.5 micrometers across – PM2.5 – may have led to 19,742 excess cases of COVID-19 and 748 excess deaths from COVID-19 during the time period. The researchers linked an astonishing 41 percent of COVID-19 deaths during the time period in Butte County to high wildfire smoke levels.
The researchers compared daily changes in PM2.5 levels and the percentage increase in COVID-19 cases and deaths in counties affected by wildfires in California, Oregon and Washington, and found “strong evidence” of a link between PM2.5 increases and increases in COVID-19 cases and deaths.
The study noted that previous studies support the plausibility of the link between wildfire smoke and COVID-19 cases/deaths:
- A study published in March found that inhalation of wildfire smoke may increase the risk of COVID-19 illness because particulate matter may transport the virus and up-regulate angiotensin-converting enzyme II (ACE-2), allowing the virus responsible for COVID-19 to enter epithelial cells.
- A study published in October 2020 found that exposure to air pollution makes our immune systems focus on bacterial/allergic immune responses instead of antiviral responses, possibly making it easier for us to develop COVID-19 infections.
- A study published in November 2020 found that exposure to air pollution, especially NO2 and PM2.5, may increase COVID-19 infections and deaths, influence COVID-19 transmission, and worsen the prognosis of those infected by COVID-19.
- Studies published in June 2020 and January 2021 found that PM2.5 could transport the virus farther than normal.
- A study published in February found that a PM2.5 concentration increase of 220.71 percent led to increases of COVID-19 cases and deaths by 56.9 and 148.2 percent, respectively.
The U.S. Centers for Disease Control and Prevention says that wildfire smoke can make people more prone to COVID-19 infections.
Sarah Henderson, the British Columbia Centre for Disease Control’s scientific director of environmental health services, told National Geographic that some cells in our bodies have small hairs that expel invading viruses out of our body through mucus.
“That’s why you blow your nose,” Henderson said.
Henderson noted that PM2.5 may destroy and block these cells, making it easier for the virus responsible for COVID-19 to get into our bodies.
Henderson also said PM2.5 may cause the immune system to attack it when it gets into our lungs, distracting our immune system and making it easier for a COVID-19 infection to take hold in our bodies.