Scientists have found a connection between the appearance of pollen in the air and the end of the respiratory illness season. They believe that the body’s immune system begins to respond to an allergen and better copes with viruses.

Modern models of influenza epidemics do not sufficiently explain its seasonality, which makes it more difficult to predict new outbreaks. After the start of the Covid-19 pandemic, the issue of more accurate modeling has become more acute. Scientists from the Open University of the Netherlands and the Erasmus Medical Center have revealed a pattern between the seasonality of diseases of this type. The main results are described in the preprint of the article published on the medRxiv.

“Meteorological factors alone, including related phenomena, do not predict seasonality, given the significant climatic differences between countries affected by influenza or Covid-19 epidemics,” the authors say. They suggest that pollen may explain the seasonality of epidemics, including Covid-19. This allergen plays a role in the activation of immunity and, apparently, creates a bioaerosol that reduces the rate of reproduction of viruses.

Specialists studied seasonal patterns of the spread of respiratory diseases for the years 2016-2020 and compared them with the plots of pollen in the Netherlands. Then they compared the incidence of influenza per 100 thousand inhabitants with weekly allergen concentrations and meteorological data.

As a result, it was possible to identify the dependence of the spread of viruses on the presence of pollen in the air: its appearance indicated the end of the flu-like illness season – and vice versa. The dependence was more noticeable after taking into account the incubation time of the virus. Also, its distribution was slowed down by solar activity: moreover, air temperature, scientists note, does not matter, in contrast to air humidity, which is associated with an increase in morbidity.

Explain the spread of the virus only by weather conditions is impossible, the researchers say. WHO notes that exposure to the body of the sun or high temperature does not prevent the risk of getting sick, in addition, Covid-19 is distributed regardless of the climate. Nevertheless, pollen and dry weather can actually destroy micro drops that contain the virus and thus slow down its spread a little.

The group concluded that pollen could predict the end of the respiratory illness season and that solar radiation affects the incidence rate. The authors believe that their study will help build a model of the seasonality of the disease and predict its outbreaks in the future.

According to preliminary findings, the distribution of coronavirus will decrease in summer and grow in autumn and winter when flowering ends. In particular, scientists suggest that in the Netherlands a new outbreak will begin 33 weeks after the concentration of pollen in the air decreases.