In the last two weeks (ending November 21), US COVID stats continued to be driven by a major outbreak in the central part of the country, with relatively modest spread in the coastal regions.

These time-lapse maps from the New York Times show how the current outbreak started in the Upper Mississippi River valley and spread from there.  Just note the NYT changed its color coding between the second and third maps which make the outbreak appear worse.  Nonetheless, the sequence clearly shows the geographic pattern of the current outbreak.

Hospitalizations

There was another large increase in the number of COVID patients hospitalized in the US, shattering the previous records.  Total hospitalizations and ICU bed usage jumped by just under 50%.  More ominously ventilator use increased by over 70%.

One difference in this surge in hospitalizations and the previous two is that this one is geographically disbursed.  The numbers were up just about everywhere in the country but most dramatically in the Midwest and the Great Plains.  As a result, there are relatively few areas where hospital capacity is truly overwhelmed.  There are a some, like Wisconsin and El Paso, that are seriously stressed but nothing like what we saw in New York in the spring.

There was perhaps a very faint light at the end of the tunnel toward the end of the two-week period as the growth in hospitalizations began to slow.  Some hot spots saw their numbers begin to level out or even decline.  For example, hospitalizations in Wisconsin and El Paso both declined about 10% in the last week.

Fatalities

Average daily fatalities also increased, moving from 900¹ in the previous two-week period to 1,270 over the last two weeks and accelerating.  The average for the last seven days was 1,440.  This is still well below the highs of over 2,000 daily fatalities in the spring, and like hospitalizations were disbursed over a much larger geographic area.

The 30-day lagging fatality rate has moved up slightly over 2%.  I continue to believe we are going to see that drop as the large increase in testing/cases works its way into the denominator.  The IHME model has once again slightly raised its year-end fatality estimate, now pegging it at almost 337,000.  That implies over 2,000 fatalities per day between now and the end of year.

Testing/New Cases/Positivity

US testing increased another 25% over the last two weeks, averaging nearly 1.6 million tests per day.  Saturday set a new record of 1,977,440 test results returned.  We will almost certainly see the 2 million mark passed this week.

The number of new positive cases jumped again, 91,000→153,000 (+69%).  The ratio of tests coming back with a positive result moved up from 7.3% to 9.8%.  Since the increase in positive test results outstripped the increase in new tests by a little more than a 2-to-1 ratio, it is fair to assume that about a third of the new positive tests can be explained by increased testing, about two-thirds is likely due to a more rapid spread of the virus.

Summary

The different regions in the U.S. basically fall into two categories at this point.  The Northeast and the Sunbelt, which saw their big surges in the spring and summer, respectively – and the middle part of the country that is experiencing a major surge now.  The future course of the pandemic will be controlled by two factors.

First, will the outbreaks in the middle of country follow the same basic bell curve we saw in the Northeast and the Sunbelt outbreaks?  Farr’s Law holds that they will.  If that is the case, then the question become s how close they are to the peak of the curve and how steep will the decline down the back side of the curve be.

The second question is whether the areas that saw a large surge earlier are susceptible to another one.  That will depend on whether there is enough naturally acquired immunity to offset the rate at which social interaction is returning to normal.

Unfortunately, we do not know the answer to either question.  My guess is that the outbreaks in the middle part of the country will wane over the next month, similar to what we saw in the Northeast and the Sunbelt.  Whether the regions that had a surge in the spring and summer will see another is, I think, much more of an open question.

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Note 1 – I reported to you two weeks ago that the average daily fatalities for that week was 870.   However, in the interim, several states revised their fatality counts, raising it to 900.