Corona current: pollen count could increase the risk of infection

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New study
Corona current: pollen count could increase the risk of infection

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Stephanie Pingel

by Stephanie Pingel

A new study shows that the number of corona infections increases on days with high pollen count. But how big is the risk really?

Spring is a double-edged sword: some are happy about rising temperatures and blooming flowers, others complain of allergy symptoms such as runny nose, itchy eyes and the urge to sneeze due to the strong pollen count. But what does the upcoming pollen season mean for the spread of the coronavirus? A team of international researchers headed by the Technical University of Munich (TUM) and the Helmholtz Zentrum München compared data from more than 31 countries. The result of the study: On days with a particularly large amount of pollen dust, the risk of being infected with coronavirus increases. It does not matter whether you have an allergy yourself.

More infections from pollen?

The investigation is limited to a period from mid-March to May of last year. At this time, the first corona wave reached Europe and North America, and the pollen count increased at the same time. With a lot of pollen in the air, the number of infections rose on average over the following four days. In general, the researchers compared the following data:

  • Weather data
  • Corona measures used and reported infection numbers
  • Information on pollen count

In general, the pollen count, together with temperature and humidity, can explain an average of 44 percent of the variance in infection rates in different regions, according to the scientists in the specialist magazine PNAS to report. It also played a role whether the region in question was in a lockdown: in some German cities, up to 500 pollen per cubic meter was collected per day. At the same time, the coronavirus infections rose by more than 20 percent. If lockdown regulations were in effect during the same period, the number of infections was halved on average with a comparably high pollen concentration.

Immune system is distracted

But why does the pollen count affect the infection process? The researchers suspect that the immune system, when pollen is flying, focuses more on this pollen and less on viruses, found in the airways. The body then produces, among other things, fewer so-called antiviral interferons, which play a major role in eliminating the viruses. By distracting the pollen, the viruses have an easier time. The study result fits in with existing studies, according to which this effect also occurs with cold viruses.

Several possible influencing factors as a weakness of the study

However, the study has a weakness typical of such studies: even when the researchers use all available verifiable data, there is no proof between cause and effect. What specifically means here Although it can be observed that the pollen count and the increased number of infections correlate, it cannot be proven that the more frequent infections are actually due to the pollen. There are various possible influencing factors here – for example the lockdown mentioned above, the weather situation, which favored the pollen count, or sunshine, which increasingly lured people outside.

This could also explain the second wave of infections in autumn and winter, when the pollen count is rather low. Study author Stefanie Gilles from the Technical University of Munich said this when asked by the Mirror: "Sars-CoV-2 infections are not caused by pollen, but by contact with infected people. Falling temperatures and the corresponding behavior of people (i.e. staying in closed, heated rooms with poor ventilation) lead – presumably – to higher infection rates in the Autumn and winter, as we know from other respiratory viruses. During this period, pollen does not play a role. "

The researchers are therefore aware of the general problem. However, the fact that, despite all these possible influencing factors, a connection between the pollen count and the increased number of infections has been established is what the experts rate as proof of their theory. That is why it makes sense, especially for high-risk groups, to pay attention to the pollen forecast in the next few months and to stay at home earlier on days with high pollen counts. If this cannot be avoided, so-called dust filter masks can also help.

Swell: spiegel.de, tagesschau.de, PNAS

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