News – In the spring of 2020, the outbreak of coronavirus infection appeared to coincide with the pollen season of trees in the northern hemisphere. These observations prompted an international team of researchers to conduct a wide-ranging study: The scientists wanted to find out if there is a clear link between air pollen density and SARS-CoV-2 disease levels.
Pollen is an environmental factor that affects disease rates
Under the leadership of first author Athanasios Damialis, the team of Chair of Environmental Medicine at TUM collected data on air pollen concentrations, weather and SARS-CoV-2 diseases – noting the day-to-day variation of disease rates and the total number of positive tests. In their calculations, the team also included data on population density and the impact of locking measures. The 154 researchers analyzed pollen data from 130 stations in 31 countries on five continents.
The team showed that air pollen can account, on average, for 44 percent of the difference in disease rates, with humidity and air temperature also playing a role in some cases. At times without locking rules, disease rates were on average 4 percent higher with each increase of 100 grains of air pollen per cubic meter. In some German cities, concentrations of up to 500 grains of pollen per cubic meter per day were recorded during the study – leading to an overall increase in disease rates of more than 20 percent. In regions where locking rules were in place, however, the incidence of diseases was on average only half as high at relative pollen concentrations.
Air pollen weakens the immune response
High pollen concentrations lead to a weaker immune response in airways to viruses that can cause coughing and colds. When a virus enters the body, infectious cells usually secrete messenger proteins. This is also true with SARS-CoV-2. These proteins, called antiviral interferons, target nearby cells to increase their antiviral immunity to keep the invaders away. In addition, an appropriate inflammatory response is activated to fight the viruses.
But if air pollen density is high, and pollen grains are incorporated into the viral granules, fewer antiviral interferons will be formed. The beneficial inflammatory response itself is also affected. Therefore, on days with a high concentration of pollen, it can lead to an increase in the number of respiratory illnesses. This is also true for Covid-19. It does not matter if the different types of pollen are allergic.
“You can’t avoid air pollen,” said Stefanie Gilles, who is also the study’s first author. “Therefore, people in high-risk groups should be informed that high levels of air pollen accumulations lead to an increased susceptibility to viral respiratory tract diseases.” Athanasios Damialis affirms: “When ‘study the spread of SARS-CoV-2, environmental factors such as pollen must be taken into account. Increased awareness of these effects is an important step in preventing and reducing the effects of Covid-19. “
Grain seed masks provide protection
What can vulnerable people do to protect themselves? Claudia Traidl-Hoffmann, a former author and professor of environmental medicine, is advising people at risk to monitor pollen predictions over the coming months. Claudia Traidl-Hoffmann says: “Wearing a particulate seed mask when pollen density is high can keep both the virus and pollen out of the airways.”
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Further information:
Claudia Traidl-Hoffmann is Professor of Environmental Medicine and for several years has conducted research for several years with her team as part of TUM’s UNIKA-T research network. She is Head of the Chair of Environmental Medicine recently transferred to the Medical Faculty of Augsburg University. She is also Director of the Institute of Environmental Medicine at Helmholtz Zentrum München and Director of the University Patient Clinic for Environmental Medicine at Augsburg University Hospital. She also teaches at the Institute for Food and Health (ZIEL) at TUM, and at other institutions.