A new European study has investigated potential correlation between high concentrations of airborne pollen and high rates of infection with SARS-CoV-2 – the virus that causes COVID-19 – while a new computer model suggests tree pollen could facilitate transmission of the virus in a crowd of people gathered outdoors.
Physicists at the University of Nicosia in Cyprus, who modelled pollen spread from a willow tree through a nearby crowd with each person at least 2 metres apart at a wind speed of 4km/ hour, have claimed 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’, reported medicalnewstoday.com.
The model simulated movement of 10,000 individual grains of pollen through groups of either 11 or 97 people around 20 metres from the tree.
The larger crowd temporarily trapped the airflow and the pollen i carried, which ‘would have the effect o increasing potential contacts between pollen grains and the tiny droplets of saliva generated when people talk, cough and so on’.
Assuming the virus can ride on pollen grains, the results published in the journal Physics of Fluids suggest the pollen ‘could carry the virus from one person to others in a crowd’.
Researchers Professor Talib Dbouk and Professor Dimitris Drikakis were inspired to conduct their study after noticing correlations between airborne concentrations of willow oak and white willow pollen in the US in March-May 2020 and SARS-CoV-2 infection rates.
Professor Drikakis commented: ‘People should avoid crowd gatherings close to some types of plants or trees known to be very active in pollen grains release during pollination season’.
Other research linking pollen levels to SARS-CoV-2 transmission includes a March 2021 study published in pnas.org which found airborne pollen concentrations in 31 countries accounted for 44% of the variability in SARS-CoV-2 infection rates.
However, German scientists at the Helmholtz Centre for Environmental Research in Leipzig, who analysed pollen from local air samples and conducted lab tests on purified pollen found ‘no evidence the pollen could carry or transmit SARS-Cov-2’.
While lead researcher Dr Susanne Dunker said they were ‘unable to completely rule out the possibility’ that pollen can transmit SARS-CoV-2, ‘we could only show that both do not form a ‘stable connection’ when co-incubated in a suspension’.
With other research suggesting an alternative suggestion for correlation between pollen levels and COVID-19 is that ‘immune reactions to pollen can make individuals more susceptible to infection’, editors at medicalnewstoday.com summed up: ‘More research is necessary to disentangle the relationship between pollen and SARS-CoV-2.’
