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The more pollen in the air, the more corona infections there are

The more pollen in the air, the more corona infections there are. A worldwide study shows this.

The coronavirus may benefit from a weakened immune system due to exposure to pollen. This is not only the case with hay fever patients, but also for people who are not allergic. The Leiden University Medical Center (LUMC), the Elkerliek hospital and Wageningen University & Research, among others, were involved in a major study from the Netherlands. The results are published today in the scientific journal PNAS.

Corona benefits from pollen

It was already known that exposure to pollen in the spring reduces the immune system against viral infections in the respiratory tract. This is the case, for example, with the cold virus. This effect occurs both in people who are allergic to pollen and people who are not allergic. During the outbreak of the coronavirus, it was noticeable that in several countries the acceleration in the increase in the number of infections only started when the pollen concentration increased. As a result, researchers suspected that the coronavirus could also benefit from a weakened immune system due to pollen exposure. Last summer, the Netherlands had its last pollen peak at the end of July.

Worldwide more pollen, more infections

To find out, a team of 150 scientists examined pollen counts from 130 pollen counting stations in 31 countries, including the Netherlands. This pollen effect was visible all over the world at the start of the epidemic. The study shows that the contamination rates increased after an increase in the concentration of pollen four days earlier. The contamination figures increased by an average of 4 percent when the pollen concentration increases by 100 pollen per cubic meter. After the introduction of a lockdown, this effect halved, but the reinforcing influence of pollen was still visible.

Also the case in the Netherlands?

This reinforcing effect was also visible in the Netherlands, but this has weakened after strict statistical testing. Several rigorous statistical tests were used to investigate whether there was a link between pollen and COVID-19. A challenging analysis, the researchers found, because it involves a large amount of information and many different factors that determine the degree of infection of the corona virus. In addition, data collection for this study stopped after April 8, as a result of which a large part of the spring pollen peak in the Netherlands was not included in the analysis. Partly because of this, the relationship between pollen and COVID-19 could not be clearly demonstrated in the Netherlands.

Follow-up research on pollen needed

The article in PNAS thus suggests that pollen exposure is contributing to the increase in corona infection rates in many countries. Whether this also applies to the Dutch situation will have to be further investigated. It must also be investigated whether the relationship found is causal. International studies are underway in which cells from the lung are exposed to pollen and the corona virus. Studies like this make it much easier to determine whether exposure to pollen actually weakens the body’s defense mechanism against the virus.

Testing for complaints

The complaints of hay fever can be confused with the complaints of COVID-19. Most of the time, hay fever does not cause a fever or a loss of smell; these are symptoms of corona. The government’s advice ‘if you think about testing, get tested’ also applies now.

Hay fever is more than just sniffling a little

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More corona infections due to pollen in the air


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