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.

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.

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.

On days with high pollen counts, try to stay indoors to limit your exposure as much as possible.

When you’re outdoors, wear a mask during pollen season. Pollen grains are large enough that almost any mask designed for allergies will work to keep them out.

Mild cases of COVID-19 could also be mistaken for allergies.

As the climate changes, we’re seeing three things that relate specifically to pollen.

One is an earlier start to pollen season. Spring changes are starting earlier, and there are signals globally of exposure to pollen earlier in the season.

As you move toward the poles, where temperatures are rising faster, we found that the season is becoming even more pronounced.

Third, more pollen is being produced. Colleagues and I described all three changes in a paper published in February.

These changes in the pollen season have been underway for several decades. When my colleagues and I looked back at as many different records of pollen keeping as we could locate since the 1970s, we found solid evidence suggesting that these shifts have been happening for at least the past 30 to 40 years.

I’ve been studying climate change for 30 years. It’s so endemic of the current environment that it’s going to be hard to look at any medical issue without at least trying to understand whether climate change has already affected it or is going to do so.

(This is an opinion piece and the views expressed above are the author’s own. The Quint neither endorses nor is responsible for them. This article was originally published on The Conversation. Read the original article here.)