THERE appears to be a correlation between high concentrations of airborne pollen and high rates of infection with SARS-CoV-2, which is the virus that causes Covid-19.
A new computer model suggests that tree pollen could facilitate the transmission of the virus in a crowd of people gathered outdoors.
The model assumes that the virus can hitch a ride on pollen grains, though there is currently no direct evidence that this can happen.
An alternative explanation for the correlation between pollen levels and Covid-19 is that immune reactions to pollen can make individuals more susceptible to infection.
Two physicists have claimed that physical distancing rules designed to curb the spread of Covid-19 may be inadequate for people standing outdoors near major pollen sources such as trees and grass.
The researchers at the University of Nicosia in Cyprus modeled the spread of pollen from a willow tree through a nearby crowd of people, each standing at least 2 meters apart, at a wind speed of 4 kilometers per hour.
The model simulated the movement of 10,000 individual grains of pollen through groups of either 11 or 97 people around 20 meters from the tree.
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The scientists found that the larger crowd of people temporarily trapped the airflow and the pollen it carried.
This would have the effect of increasing potential contacts between pollen grains and the tiny droplets of saliva generated when people talk, cough, and so on.
Assuming that the virus can hitch a ride on pollen grains, the results suggest that the pollen could carry the virus from one person to others in the crowd.
Talib Dbouk, Ph.D., and Dimitris Drikakis, Ph.D., from the university’s Defence and Security Research Institute conducted the study, which has been published in the journal Physics of Fluids.
The researchers point out that droplets of saliva are relatively heavy and evaporate rapidly, whereas pollen grains contain little water, are lighter, and can travel tens of kilometers.