Pollen count linked to coronavirus infections

A higher pollen count in the air may result in higher coronavirus infections, according to a worldwide study that included researchers from Leiden University Medical Center (LUMC), Elkerliek Hospital, and Wageningen University & Research in the Netherlands.

As with other infections like the cold virus, it seems that pollen exposure reduces the immune system's ability to block a Covid-19 infection, both in people who suffer from hay fever and people who do not have a pollen allergy, according to the researchers.

During the first outbreak of the coronavirus, it was noticeable in several countries that the number of Covid-19 infections only really started to climb after the pollen concentration increased. A team of 150 scientists therefore decided to examine pollen counts from 130 pollen counting stations in 31 countries, including the Netherlands, and compare that to coronavrus infection numbers, LUMC said in a statement.

They found that, on average, Covid-19 contamination figures increased four days after pollen concentrations increased by 100 pollen per cubic meter. This effect halved after the introduction of a lockdown, but the reinforcing effect of pollen was still visible. The fact that infection rates only increased four days after pollen concentrations went up, is in line with the 4 to 5 days incubation period of the coronavirus.

The researchers stressed that the positive correlation between pollen and Covid-19 is not because pollen helps spread the virus, but rather because pollen weakens people's resistance to infections.

LUMC suggested further to find out whether this also applies to the Dutch situation, and whether the link found is causal.