Post #1105: COVID-19 trend to 4/9/2021, Michigan as a perfect storm

Posted on April 10, 2021

Source for this and all other graphs of new cases:  Calculated from The New York Times. (2021). Coronavirus (Covid-19) Data in the United States. Retrieved 4/10/2021.  The NY Times U.S. tracking page can be found at

I think the graph above appropriately characterizes the situation.  There’s an outbreak in Michigan.  And everything else is a jumble of modest up or down trends.  The resulting U.S. average result is still “no trend to speak of”, as shown below.

But why is Michigan so different?

First, per my analysis, based on the most recent CDC data on the new variants, the underlying story here really is a race between the more-infectious U.K. COVID-19 variant (B.1.1.7) and COVID-19 immunity via prior infection and vaccination. Anything I said to the contrary, before that, is obsolete based on the newer, more complete information from CDC (Post #1101).

The only thing my analysis adds is that there appears to be a difference between the warm-climate states and the cold-climate states.  Florida and Texas have nearly as much incidence of the U.K. variant as Michigan and Minnesota.  But they have nothing like the sharp upward trend in new cases currently observed in Michigan.  So the story isn’t as sample as the U.K. variant being a huge problem.  Something more is needed to get an Michigan-like outbreak, versus a Florida-like slight upward trend.

Maybe that’s worth graphing.  Here are the top five states, in terms of incidence of the U.K. variant, per the U.S. CDC:

Interestingly, those states sort out in very nearly their rank by existing COVID-19 immunity from prior infections.   Like so:

And so, if I had to guess why Michigan is so different, it’s a perfect storm.  It combines the highest rate of incidence of the U.K. variant, the lowest rate of existing immunity to COVID-19, and a cool climate.  (The last one appeared as an independent predictor of an upward trend, in my statistical analysis, independent of immunity via prior infections.)

In one of those sad, ironic twists, their success in avoiding infections from the garden-variety COVID-19 variant earlier in the pandemic has left them open to a massive outbreak from the U.K. variant late in the pandemic.

But my upbeat conclusion is that we are unlikely to see the rest of the states take off as Michigan has.  I.e., still no evidence suggesting a big fourth U.S. wave, despite what’s occurring in Michigan.

Instead, Michigan’s outbreak seems to be the result of  factors unique to that situation.  They have just, unfortunately, maxed out on all the risk factors this time around:  High U.K. variant incidence, low existing immunity via prior infections, and cool climate.

Helix corporation data and the current incidence of the U.K. variant by states.

As an interesting side note, the state cross-section of the Helix Corporation data on U.K. variant incidence seem to line up nicely with the CDC data.  (The advantage of the Helix data is that they are timely, where the CDC data are more than a month old).

As of April 6, 2021 reporting data, Helix now shows that about 80% of new cases in Michigan are the U.K. variant.  Versus about 75% for Minnesota, and maybe 70% for Florida or Texas.  But they also shows that about 65% of all U.S. cases are now the U.K. variant.  So these states remain ahead of the pack, in terms of the incidence of the U.K. variant, but not by a whole lot.

But that’s good news.  Once you’re at the point where almost two-thirds of new cases are the new variant, but there’s no strong trend, and vaccinations continue to increase (below), it gets really hard to argue that there should be some huge U.S. fourth wave.  As I said almost a month ago, I just don’t think that’s going to happen.

Data sourced from the Helix® COVID-19 Surveillance Dashboard. Accessed at on 4/10/2021.

The elderly are still getting vaccinated.

If you want to read more detail on what’s behind these numbers, see Post #1094.  In particular, the rate of increase see-saws with a regular weekly pattern.  That said, on average, another half-percent of the elderly got vaccinated, per day, for the past three days.  FWIW, that final number of 77.4 already exceeds anything I thought was remotely plausible, based on all existing survey information.

Maybe when push comes to shove, people will do the responsible thing?  Hard to believe, yet it might be true.