Post #882: Does mask use really reduce COVID-19 spread?

Posted on October 28, 2020

Source:  Mid-July mask use data from   NY Times poll.  Case counts from Virginia Department of Health.  Data points are counties (plus independent cities) of Virginia with 25,000 or more population.

Yeah, correlation is not causation.  But it’s an amazement to me, given quality and age of the mask use data, that you can see any correlation at all between mask use and the rate of new infections.

That NY Times poll shows that about 67% of Virginians who responded to the survey said they “always” wore masks when out of the house.  The prediction from that regression line is that if we could add 33% to those who “always” wore them, new cases / 100,000 / day would drop by 10 percentage points.  It would all-but-eliminate the new cases in Virginia.

Not gonna happen.

But I’m really showing this now, to put down a marker.  If my hypothesis about dry air is right (Post #880) — dry indoor air plus no masks explains both Wave 2 and Wave 3 of the U.S. pandemic — then our Virginia case counts are going to start climbing as the outside air temperatures drop, and indoor air relative humidity drops.  But that should hit the low-mask-use areas hardest.  So I’m getting set up to test that, sometime around New Year’s Day.