Post #1216: COVID-19 Delta wave, is this the peak?

Posted on August 19, 2021

Today the U.S. stands at 43.5 new COVID-19 cases per 100,000 population per day.  That’s not materially different from yesterday.  That figure grew just 13% over the last seven days.

There are still a lot of states where new case counts are rising.  But as of today, we have six states where new case counts have fallen over the past seven days.

More importantly, if we focus on the half-dozen states that collectively account for half of all new U.S. COVID-19 cases, four of them appear to have reached a peak.

It’s fairly clear that the top of the U.S. Delta wave is not far off.  We’ll only know in hindsight, but it might even be today.

If you’re not vaccinated yet, don’t get vaccinated for the Delta wave.  It’s way too late for that.  Get vaccinated in anticipation of the U.S. winter wave.

Data source for this and other graphs of new case counts:  Calculated from The New York Times. (2021). Coronavirus (Covid-19) Data in the United States. Retrieved 8/18/2021, from”  The NY Times U.S. tracking page may be found at

As you can see from the graph above, the U.S. line is almost horizontal at the right-hand end.  By eye, you might imagine that turning downward now, or you might see it as likely to drift upward for a few days yet.  Either way, the peak appears near.

You can get to the same conclusion by looking at the trend in the trailing seven-day growth rate, graphed below.  Continue the blue line out, by eye, for another seven days.  (More-or-less to the extreme right edge of the graph.)  To me, that surely looks like it will have hit zero by then.

It’s not even very hard to understand why we’re seeing this.  We’re seeing peaks in most all the states that matter, in terms of new U.S. COVID-19 cases.  Below you see the six states accounting for half of new U.S. COVID-19 cases in the past week.  I’d say that four out of six are flat — at their peak — right now.

Obviously, it’s too soon to declare victory and go home.  But absent some absolutely unprecedented change in the trends, the U.S. as a whole is at or near the peak of the Delta wave now.

I will note that this is significantly earlier than I would have guessed.  A few days ago, it still looked like the peak would be maybe three weeks from now.  I’m not unhappy to have been wrong.