Spring is coming and with it the flowering of many trees and shrubs, the cause of many allergies. Sufferers know that exposure to pollen weakens immunity against some seasonal respiratory viruses and decreases the antiviral response of interferon.
Today, however, there is greater attention on the subject: a study published in Pnas has in fact investigated the association between SARS-CoV-2 infection and concentrations of airborne pollen. Can pollen exposure increase susceptibility to new coronavirus infection?
Pollen allergy: there are now more than one seasons at risk
by Paola Mariano
Athanasios Damialis of the University of Augusta and colleagues, authors of the study, conducted cross-sectional and longitudinal analyzes of data on pollen, meteorological factors and SARS-CoV-2 infection rates. The initiative kicked off when, between 10 and 14 March 2020, a large-scale heat wave kicked off the first major seasonal spike in tree pollen emissions across much of the Northern Hemisphere. This coincided with high infection rates of SARS-CoV-2, characteristic of the first exponential phase of the infection.
The survey carried out covered 130 regions in 31 countries on five continents. The relationships between daily pollen concentrations and SARS-Cov-2 infection rates were investigated. The analysis took into account multiple factors including temperature, humidity, population density and isolation status.
Pollen cocktail for early blooms and fine dust: the allergy season has already started
at ALESSANDRA CORICA
The results reveal that simultaneous exposure to SARS-CoV-2 (through other infected human carriers) and airborne pollen can, under “favorable” weather conditions, promote viral infection. Pollen, alone or in combination with temperature and humidity, could explain, on average, about 44% of the variability in the infection rate. According to the study, infection rates actually increased after higher pollen concentrations. At the same time, lock-down countries had daily infection rates equal to half that of countries not in isolation at similar pollen concentrations.
However, the authors point out that the correlations demonstrated suggest that pollen is a modulating factor for the progression of SARS-CoV-2 infection, but there is no evidence that airborne pollen grains are themselves carriers of particles of virus. Without contact, there is no risk of infection.
The good news? For those with spring-related allergies, this year will be better
FABIO DI TODARO
As for the future, it is not yet known whether other particles, meteorological variables and air pollutants could play a role in the spread of the covid. Although there is published evidence on the effects of various environmental parameters, such as nitrogen dioxide (NO2), particulate matter (PM2.5) and ultraviolet radiation. But for pollen, based on the results to date, since we cannot avoid their exposure, the only recommendation is to always use particle filter masks, even more so during the spring.
.