Seasonality of common human coronaviruses (other than COVID-19) in Stockholm, Sweden. Source:
Potential impact of seasonal forcing on a SARS-CoV-2 pandemic DOI: https://doi.org/10.4414/smw.2020.20224 Publication Date: 16.03.2020 Swiss Med Wkly. 2020;150:w20224 Neher Richard A., Dyrdak Robert, Druelle Valentin, Hodcroft Emma B. Albert J.
Part 3 of my hard winter postings is about, well, winter. You’re probably starting to see some newspaper coverage of the recent up-ticks in cases here and in Europe. People are speculating that this may be due to the change in the weather.
The long and the short of it is that in a cold climate (as pictured above), every common human coronavirus exhibits a wintertime peak. (As do most strains of flu.) So it would not be surprising if that were also true of COVID-19.
I did a brief review of the mechanisms behind this in the middle of Post #829, including a quick-and-dirty review of the scholarly literature. The quick upshot is that the environment that maximizes your risk of transmission of COVID-19 is cold, dry, stagnant air. In short, for avoiding COVID-19, the warmer, the wetter, and the windier the better.
And so, as temperatures fall, and relative humidity declines, and we move inside, opportunities for COVID-19 infections increase.
Not much you can do about it, as a population. For sure, I’ll be running a humidifier all winter. And I note that one of the advantages of wearing a mask, in public, is that it keeps your nasal membranes from drying out, which is an advantage in avoiding infection (on top of the filtration ability of the mask).
But in the end, it’s all a game of probabilities. And so far, everything I’ve read — from the actual behavior of other members of this family of viruses in Stockholm, to the measured survival times of COVID-19 under varying conditions of heat and humidity — suggests that we’re like to see greater rates of transmission as we head into winter. At least in the colder parts of the U.S.