I previously documented the spike in COVID-19 cases that South Dakota is seeing in the weeks after the Sturgis bike rally, and how the host counties in particular are left with a nasty spike.
I noticed something today.
Today I noticed that the Midwest has had an increase of about 20% over the last week. I know that Sturgis draws a lot of visitors from the neighboring states, and that visitors from even farther away would be transiting through those states...I wondered if there was a pattern.
I looked up the COVID confirmed case rates for South Dakota and the states that border it (my experimental group!), checking the latest 7-day average vs. two weeks ago, about the earliest that a spike could possibly be detected.
I then pulled the numbers on all the other Midwest states, my control group.
South Dakota was, unsurprisingly, the one with the highest increase. But the average increase (simple mean of the state averages) was 56% over the last two weeks.
For the other midwestern states it was only a 9% increase, and the nation as a whole is down almost 20%.
Here's what the last month looks like visually. This plot includes all the midwest states, with Wyoming and Montana added.
Obviously, Sturgis isn't the only thing that happened in the Midwest in August, Iowa's storms on August 10-11 likely causes a lot of extra travel, and likely some delays in testing. And correlation doesn't prove causation. But it is suggestive - the Midwest is the only region rising, the rise is led by South Dakota and the states bordering it.