Post #1106: COVID-19 trend to 4/11/2021

Posted on April 12, 2021


Opinions vary on what’s going to happen next in the U.S. fourth wave of COVID-19.  At one end of the spectrum, there’s the CDC director, talking up “impending doom” from the U.S. fourth wave.  And you’ll see sporadic newspaper stories where some expert will opine that a massive U.S. fourth wave of COVID-19 is approaching.  Or might be approaching.  Or at least remains enough of a likelihood that you should keep up your COVID-19 hygiene and get yourself vaccinated.

My post today is a reaction to a news article proclaiming that we’re all going to go the way of Michigan.  With, as far as I can tell, zero hard analysis to back that up.  Certainly, nothing like a statistical analysis of the state-level data (Post #1101), or a detailed outline of the factors that make Michigan particularly vulnerable (Post #1105).

Near as I can tell, that’s straight-up fear-based journalism.  The article more-or-less blames the people of Michigan for being a bunch of COVID-19 hygiene slackers.  When, in fact, that’s just not objectively true.   Or, at least, they’re no worse than 35 or so other states.

Source:  Carnegie-Mellon University COVIDCAST, accessed 4/12/2021.

And so, this post is my way of saying that I disagree.  I disagree with “impending doom”.  I disagree that all U.S. states will inevitably follow in the footsteps of Michigan.

In this post, I present the usual update on trend.  And, for what it’s worth, give you my assessment of the situation.  In a nutshell, I still think that the U.S. fourth wave of COVID-19 will be the “fizzling out” wave.

Gaining coherence, but not momentum

If I had to sum it up, it looks like the U.S. fourth wave of COVID-19 is only just now starting to gain some coherence.  More U.S. states are now moving into a slow upward trend in new COVID-19 cases per day.  As a result, what was chaotic at the start of the U.S. fourth wave is now starting to look like a national trend.  Nothing nearly as clear as the U.S. third wave.

But the key is that it’s a slow trend, and that, Michigan (and possibly Minnesota) aside, there are few places that look remotely like an outbreak.

Or maybe that’s just my imagination.  See for yourself (below).  To me, looks like most of the states are starting to show an upward trend.  But outside of maybe two states, nothing like a massive fourth wave of COVID-19.

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 4/12/2021.  The NY Times U.S. tracking page can be found at

The U.S. as a whole is showing a 10 percent per week increase in daily new COVID-19 cases.  Most of the regions are trending upward.  But most aren’t trending upward very fast.

Other items of note

1:  California data anomaly.  There’s a sharp uptick in cases in California, but that’s just a data reporting anomaly, per their state dashboard.  CA is so large that this probably bumps the national number up a bit.  The rest of the Pacific region is showing a clear upward trend.

2: Michigan gets a little break, Minnesota does not.  Probably just random variation.  Note  that the clear majority of Midwest states are now rending modestly upward.  My last post on trends outlined why I think Michigan is such an outlier, starting with the low fraction of the population immune to COVID-19 via prior infection (Post #1105).

3:  Florida showing a clear but slow increase.   But you need to keep in mind that as of April 6, almost 70 percent of Florida cases were the more-contagious U.K. variant B.1.1.7  (Per the Helix® COVID-19 Surveillance Dashboard. Accessed at on 4/12/2021.)  I think it’s safe to say that, by now, three-quarters of new cases in Florida are the U.K. variant.  So, if that trend is about as bad as it gets in the typical state, the U.S. fourth wave will be nothing like the third.

4:  No trend in Texas.  You’d be hard-pressed to say that Texas has anything resembling an upward trend.  And Texas is near the top of the list for prevalence of the U.K. variant.  As of April 5, 68% of new cases were the U.K. variant (five-day moving average, per the Helix dashboard cited above).  So, ditto the comment about Florida.

5:  Colorado splits away from the rest of the Mountain states.  Coincidence or not, Colorado is also the Mountain region state with the highest prevalence of the U.K. variant B.1.1.7. (see below).    And, much like Michigan, it was relatively unscathed in the first rounds of COVID-19.  (As of 3/1/2021, 7.9% of CO residents had been diagnosed with COVID-19, roughly halfway between the Michigan figure of 6.5% and the U.S. state median of 9.2%).  And it’s what I would classify as a cold-climate state.


Source: CDC.  NOTE that these numbers are about six weeks old, and that the percentages will have increased substantially by now.

But unlike Michigan, Colorado does not appear to have opened all of their grade schools yet (per this newspaper reporting).  That differs from Michigan, where the outbreak has centered around high school students, and young adults.

So Colorado situation is similar to Michigan in some respects, and different in others.  Not quite as high a proportion of the U.K. variant, not quite as low a fraction already immune to COVID-19 via infection, and the schools are not quite as open as they are in Michigan.

6:  New York and New Jersey take a pause.  Is that it?  Is that the fourth wave for those states? Wouldn’t that be nice, if true.

7:  The elderly continue to get vaccinated.  The fraction vaccinated continues to grow by a half-percentage-point per day.  This is now far higher than anyone would have predicted based on survey data.  Recall that those vaccine counts are a lot odder than you might think, and that the growth rates for these see-saw over the course of a week (Post #1094).  But it’s undeniable that we still have not reached the upper limit of COVID-19 vaccine acceptance in the elderly.


My crude little statistical analysis (Post #1101) lines up with the current story on COVID-19.  Near as I can tell, we are in a race between the spread of the more-infectious U.K variant B.1.1.7, and the immunity of the population via prior infection and current vaccination.

But, that’s as far as I think that story can be pushed.  It’s a race.

Part of the issue is that the vaccine isn’t as effective as it has been touted, for stopping the pandemic.  That has nothing to do with medicine, and everything to do with behavior.  It was targeted first at the elderly, but it’s the young who by-and-large are currently spreading the virus.  And it’s a pretty good guess that it’s been taken first by the cautious, health-conscious fraction of the population that would have been least likely to spread disease in the first place (as argued in Post #1080).

So it’s a race between B.1.1.7 and vaccination.  And vaccination has those handicaps.

Even with that, of those descriptions of the likely future, at the start of this post,  I’m only buying into the last one.  Don’t let your guard down, and get vaccinated.  That’s just common sense. I don’t think you need a doomsday scenario to sell that to the average American.

I don’t think there’s going to be a massive fourth wave.  I said that almost six weeks ago, and I haven’t seen anything yet to change my mind.  At this point, if you look at the most populous U.S. states, and look for a trend in daily new COVID-19 cases, you have, in order:

  • California — no upward trend yet.
  • Texas – saturated with B.1.1.7, slight downward trend.
  • Florida – saturated with B.1.1.7, slight upward trend.
  • New York — slight downward trend.
  • Pennsylvania — no trend.

Michigan is an outlier, and I think they are suffering from a unique combination of circumstances (Post #1105).  To be clear, I don’t think Michigan is the bellwether for the U.S. as a whole.  I think it just has an unfortunate combination of bad luck and bad decisions regarding schools.

In short, I think the pandemic is in the process of fizzling out in the U.S.  Sure, the trend is up, and more states seem to be joining that trend.  But most of those trends are quite slight.  No matter how I look at it, I just can’t see the current situation as some sort of gathering storm.

Instead, I think that all we need to do is keep up the COVID-19 hygiene and wait for a large enough fraction of the population to be vaccinated.  That sort of common sense isn’t anywhere near scary enough to make the newspapers.  But after poring over the numbers, and doing a few bits of statistical analysis, it remains the best description I can offer for the current situation.