Why do you keep hearing that the US third wave of COVID-19 is getting worse, when most of the states appear to have peaked? Like so:
The answer is that the US totals reflect the US population. And the (mostly) upper-Midwest and Mountain states that have peaked are all low-population states. There was a lot of COVID-19 activity there, but there aren’t a lot of people.
By contrast, over one-third of the US population lives in just five states (CA, TX, FL, NY, TX, PA). And in those states, you are still seeing a broadly-based and slow ramp-up of COVID-19 activity. I would say that they show almost weirdly similar paths, given how different those five states are from one another.
In fact, we have to broaden the view to the top ten states (encompassing more than half the US population) before we pick up even one of those Midwest states where there appears to be a clear peak in COVID-19 activity. In the graph below, the top line is Illinois.
And so the third wave of COVID in the US has this odd multi-part nature.
First, there were crazily high growth rates for daily new COVID cases in a cluster of Midwest/Mountain states. That’s the peak of the mountain on the first graph above. All the states where the growth rate at some point exceeded 100 new cases/100,000 population/day.
Those high rates of growth seems to have “burnt out” for the time being. Most of those states appear to have peaked just prior to Thanksgiving. Why those peaks were so nearly synchronous is something of a mystery, and probably always will be. But, for at least one state — North Dakota — enough people got infected during that period that they have plausibly reached COVID-19 herd immunity, or close to it (see Post #901).
But where the bulk of US residents live, we’ve seen nothing quite so dramatic. Instead, as winter slowly settles in, the COVID-19 new infection rates have slowly risen.
What’s I find particularly odd is that “winter” means different things, weather-wise, in those different states (CA, TX, FL, NY, TX, PA). And yet, the lines on the graph look almost identical.
NY, PA, and TX all have what I would call a “traditional east coast” winter climate. If you were to look up today’s forecast for Dallas and for Philadelphia, you would be hard-pressed to tell which was which without the labels.
Florida spans everything from more-or-less that climate (in central Florida) to a subtropical climate in South Florida. And yet, the entire state shows high rates of COVID-19 activity.
California, or at least Southern California, is hot and dry right now, having recorded zero precipitation for November, and frequently recording outdoor relative humidity below 20% (due in part to Santa Ana winds).
And yet, we’re seeing more-or-less the same slow rise in new cases in all five states. I guess that’s just another seemingly random aspect of this pandemic.