A link between the incidence of coronavirus infections and high pollen counts in the air has been found in a new international study spanning dozens of countries.
High pollen counts, partially affected by air humidity and temperature, contributed to a more than 40-percent increase in coronavirus infection frequency, the study found.
Exposure to pollen weakens the immune system's defence reactions against certain seasonal viruses and can impair the ability to fight them, according to the University of Turku and the Finnish Meteorological Institute (FMI), which issued a joint statement about the study's findings.
In most cases, infection frequency increased four days after the peak pollen concentration, which roughly corresponds to the incubation period of the coronavirus. However, the phenomenon is not entirely linked to people who suffer from pollen allergies. Several other factors affect coronavirus infection frequency, according to the statement.
The statement was timed to predate Europe's pollen season and potentially limit people's exposure to it.
"It's important to pay particular attention to times when pollen concentrations are high. Exposure to pollen should be reduced, for example, by avoiding outdoor activities when pollen concentrations are high or by protecting the respiratory tract", FMI research professor Mikhail Sofiev who analysed the research data, told national broadcaster Yle.
The study also assessed the impact of the numerous restrictive measures taken to contain the spread of the virus in spring 2020.
"Restrictive measures halved the frequency of infections, compared to situations where no measures were taken, despite high levels of pollen in the air. During periods of restrictions, people are likely to be less exposed to both the virus and pollen that weakens the immune system. In the absence of restrictive measures, high concentrations of pollen can increase the frequency of infections significantly", the joint statement said.
Over 150 researchers participated in the study that compiled research material from 31 countries.
Finland, one of the least-hit Scandinavian countries, has seen over 63,100 cases of COVID-19, with 776 deaths. However, as the infection rates continue to increase, with the latest daily record of 797 cases last week, Finland has been re-introducing some of the restrictions, including the closure of bars and restaurants. The country recently entered its second state of emergency and embarked on another partial lockdown.