A study released last week suggests that the presence of pollen can make a person more susceptible to the COVID-19 virus.
The report looked at the link between the powdery substance produced by plants and how it exacerbated the novel coronavirus that has killed more than 500,000 in the United States.
According to the study, pollen allows the COVID-19 virus to gain a foothold when it suppresses the immune system’s response to the virus.
One of the study’s authors explained that researchers wanted to see how the number of new infections changed with the rise and fall of pollen levels in 31 countries around the world.
Lewis Ziska, associate professor of environmental health sciences at Columbia University, said, “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 study, published in the Proceedings of the National Academy of Sciences, looked at not only pollen levels, but such metrics as population density, temperature, lockdown restrictions and the amount of humidity on a certain day.
What the researchers found was that when pollen in an area spiked, infections spiked as well. The pollen seems to rile the immune system.
“When we inhale pollen, they end up on our nasal mucosa and here, they diminish the expression of genes that are important for the defense against airborne viruses,” Stefanie Gilles, one of the study’s authors and chair of environmental medicine at the Technical University of Munich in Germany, said in a news conference.
The reason pollen seems to be linked to an increase in COVID-19 infections, researchers said, is that pollen may cause the body to drop its defenses against the airborne virus that causes the infection.
“If you’re in a crowded room and other people are there that are asymptomatic, and you’ve just been breathing in pollen all day long, chances are that you’re going to be more susceptible to the virus,” Ziska said. “Having a mask is obviously really critical in that regard.”
Some researchers have pushed back on the study’s findings, according to WebMD.
“Just because two things happen at the same time doesn’t mean that one causes the other,” said Martijn Hoogeveen, a professor of technical sciences and environment at The Open University in the Netherlands.
Hoogeveen has also recently published a study showing that the arrival of pollen season in the Netherlands coincides with the end of flu season. The COVID-19 infection trends tend to follow a similar pattern, Hoogeveen said.
“Spring changes are starting earlier,” Lewis said in a post on The Conversation. “There are signals globally of exposure to pollen earlier in the season.”
He added that the season is also getting longer and more pollen is being produced.
“The time you’re exposed to pollen, from spring, which is primarily driven by tree pollen, to the summer, which is weeds and grasses, and then the fall, which is primarily ragweed, is about 20 days longer in North America now than it was in 1990. As you move toward the poles, where temperatures are rising faster, we found that the season is becoming even more pronounced.”
The three factors, Lewis said, lead to a worse outcome for humans.
“As climate change drives pollen counts upward, that could potentially result in greater human susceptibility to viruses.”
Lewis said the best way for people to protect themselves is to wear a mask when pollen levels are high.
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