Yesterday the Arizona Daily Star ran an article on covid-19, saying that its incidence increased ten days after Governor Ducey lifted the order closing non-essential businesses. Ten days was chosen, the article said, because that was the accepted interval between exposure and the development of symptoms. (They were a little mistaken: it’s more like five days average for symptoms to develop, plus five days average for testing results to be posted. But ten days is a good interval.

I responded with a letter to the editor, which I doubt they will publish, pointing out that by the same standard the demonstration/riot downtown on May 31 had a much worse effect. Which is just commonsense. Which is more likely to pass a respiratory virus, having your hair cut by a barber wearing a mask, or standing shoulder-to-shoulder for hours in a crowd of chanting and shouting people?

Here are my figures, taken from the Arizona Dep’t of Health Services website. I take the numbers and rate of daily increase for one day before and after the tenth day:

Business reopening, May 16

May 29: 56 new cases, 2.6% increase
May 30: 78 ” ” 3.4%
May 31: 14 ” ” 0.5%

Demonstrations/riot, May 31

June 9 189 new cases, 6% increase
June 10 129 ” ” 4%
June 11 149 ” ” 4%