Followup Study Submitted: “Pollen Explains Flu-Like and COVID-19 Seasonality”

Avatar for Martijn Hoogeveen

Our followup study to explain the seasonality for COVID-19 by looking at pollen, its antiviral and immuno-activating (hay fever) properties, has just been concluded. We also controlled for meteorological variables as solar radiation, relative humidity and temperature, and analyzed their interaction with pollen and flu-like incidence as well. The preliminary study is already published by Elsevier Science’s Science of The Total Environment.

An interview in De Telegraaf, most read newspaper in The Netherlands, with a bit provocative title invoked big online discussions. Someone posted an English translation of this De Telegraaf article. The item became De Telegraaf’s most read article, the same what happened with the FD item after the preliminary study one month earlier. Next RTL News had an item (@2m10s) about it as well. It’s clear that COVID-19, hay fever, and multi-cycle pandemics are big subjects, as is the riddle of flu-like-seasonality. We identified the predictor.

The followup study is submitted on May 19, 2020, and is now under review by the respective journal. But, we can at least share the abstract of the paper written with my co-authors Eric van Gorp, professor virology at Erasmus MC, and Ellen Hoogeveen, epidemiologist/internal medicine at Jeroen Bosch Ziekenhuis. The new study is not yet online, but here’s the abstract:

Abstract “Pollen Explains Flu-Like and COVID-19 Seasonality in The Netherlands

By Martijn Hoogeveen (corresponding author), Eric van Gorp & Ellen Hoogeveen.

Current models for flu-like epidemics insufficiently explain multi-cycle seasonality. Meteorological factors alone do not predict seasonality, given substantial climate differences between countries that are subject to flu-like epidemics or COVID-19. Pollen is documented to be antiviral and allergenic, play a role in immuno-activation, and seems to create a bio-aerosol lowering the reproduction number of flu-like viruses. Therefore, we hypothesize that pollen may explain seasonality of flu-like epidemics including COVID-19.
In this follow-up study, the Pollen-Flu Seasonality Theory is tested for 2016-2020 flu-like seasons, including the COVID-19 pandemic, in The Netherlands with its 17 million inhabitants. We combined changes in flu-like incidence per 100K/Dutch citizens with weekly pollen counts and meteorological data for the same period. Finally, a predictive model is tested using pollen and meteorological threshold values displaying inhibitory effects on flu-like incidence.
We found a highly significant inverse association of -.38 between pollen and changes in flu-like incidence corrected for incubation period, confirming our expectations for the 2019/2020 COVID-19 season. We found that our predictive model has the highest inverse correlation with changes in flu-like incidence of -.48 when pollen thresholds of 610 total grains/m3 per week, 120 allergenic grains/m3 per week, and a solar radiation threshold of 510 J/cm2 are passed. The passing of at least the pollen thresholds preludes the beginning and end of flu-like seasons. Solar radiation is a supportive factor, temperature makes no difference, and relative humidity even associates with flu-like incidence increases and pollen reductions.
We conclude that pollen is a predictor for the inverse seasonality of flu-like epidemics including the COVID-19 pandemic, and solar radiation is a co-inhibitor. The observed seasonality of COVID-19 during Spring, suggests that COVID-19 may revive in The Netherlands after week 33, the start being preceded by the relative absence of pollen, and follows standard pollen-flu seasonality patterns.

Avatar for Martijn Hoogeveen

Founder and CEO of Icecat NV. Investor through iMerge. PhD Multimedia at Delft University of Technology. Former Professor at Open University Netherlands/Technical Sciences & Environment.

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