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Pollen can raise your risk of COVID-19 – and the season is getting longer thanks to climate change

Pollen can suppress how the body’s immune system responds to viruses. Callista Images via Getty Images

Pollen can raise your risk of COVID-19 – and the season is getting longer thanks to climate change

Pollen can suppress how the body’s immune system responds to viruses. Callista Images via Getty Images

Pollen can raise your risk of COVID-19 – and the season is getting longer thanks to climate change

Pollen can suppress how the body’s immune system responds to viruses. Callista Images via Getty Images

Pollen can raise your risk of COVID-19 – and the season is getting longer thanks to climate change

Pollen can suppress how the body’s immune system responds to viruses. Callista Images via Getty Images

Pollen grains are large enough that almost any mask designed for allergies will work to keep them out.

Lewis Ziska, Columbia University

Exposure to pollen can make you more susceptible to COVID-19, and it isn’t just a problem for people with allergies, new research released March 9 shows. Plant physiologist Lewis Ziska, a co-author of the new peer-reviewed study and other recent research on pollen and climate change, explains the findings and why pollen seasons are getting longer and more intense.

What does pollen have to do with a virus?

The most important takeaway from our new study is that pollen can be a factor in exacerbating COVID-19.

A couple years ago, my coauthors showed that pollen can suppress how the human immune system responds to viruses. By interfering with proteins that signal antiviral responses in cells lining the airways, it can leave people more susceptible to potentially a whole host of respiratory viruses, such as the flu virus and other SARS viruses.

In this study, we looked specifically at COVID-19. We wanted to see how the number of new infections changed with the rise and fall of pollen levels in 31 countries around the world. We found that, on average, about 44% of the variability in COVID-19 case rates was related to pollen exposure, often in synergy with humidity and temperature.

The infection rates tended to rise four days after a high pollen count. If there was no local lockdown, the infection rate increased by an average of about 4% per 100 pollen grains in a cubic meter of air. A strict lockdown cut the increase by half.

This pollen exposure isn’t just a problem for people with hay fever. It’s a reaction to pollen in general. Even types of pollen that typically don’t cause allergic reactions were correlated with an increase in COVID-19 infections.

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