Pollen exposure weakens the immunity against certain seasonal
respiratory viruses by diminishing the antiviral interferon response. Here we investigate whether the same applies to the
pandemic severe acute respiratory syndrome coronavirus 2
(SARS-CoV-2), which is sensitive to antiviral interferons, if infection waves coincide with high airborne pollen concentrations. Our
original hypothesis was that more airborne pollen would lead to
increases in infection rates. To examine this, we performed a crosssectional and longitudinal data analysis on SARS-CoV-2 infection,
airborne pollen, and meteorological factors. Our dataset is the
most comprehensive, largest possible worldwide from 130 stations, across 31 countries and five continents. To explicitly investigate the effects of social contact, we additionally considered
population density of each study area, as well as lockdown effects,
in all possible combinations: without any lockdown, with mixed
lockdown−no lockdown regime, and under complete lockdown.
We found that airborne pollen, sometimes in synergy with humidity and temperature, explained, on average, 44% of the infection
rate variability. Infection rates increased after higher pollen concentrations most frequently during the four previous days. Without lockdown, an increase of pollen abundance by 100 pollen/m3
resulted in a 4% average increase of infection rates. Lockdown
halved infection rates under similar pollen concentrations. As
there can be no preventive measures against airborne pollen exposure, we suggest wide dissemination of pollen−virus coexposure dire effect information to encourage high-risk individuals
to wear particle filter masks during high springtime pollen
concentrations.
COVID-19 | pollen | viral infection | aerobiology