REVISED ESTIMATES (INDICATED BY STRIKETHROUGHS) TO ADJUST FOR THE ADDITION OF DATA THROUGH APRIL 1, 2020, INCLUDING PREVIOUSLY MISSING DATA FOR THE STATE OF WASHINGTON.
Using some simple linear models of the rates of growth in U.S. coronavirus cases and deaths, I predicted that cases would top out at 250,000 and deaths wouldn’t exceed 10,000. I assumed that
lockdowns, quarantines, and social distancing continue for at least two more weeks, and assuming that there isn’t a second wave of COVID-19 because of early relaxation or re-infection.
I also said that, in any event,
the final numbers will be well below the totals for the swine-flu epidemic of 2009-10 (59 million and 12,000) but you won’t hear about it from the leftist media.
Is it time for me to back off my bold predictions, in light of the “official” estimate of 100,000 to 240,000 deaths that was announced at yesterday’s White House briefing? Probably.
First, let’s look at the numbers:
- The Spanish flu pandemic of 1918-19 resulted in a maximum of 675,000 deaths out of 29 million U.S. cases — a fatality rate of 2.4 percent.
- The H1N1 pandemic of 2009-10 resulted in 12,000 deaths out of 59 million U.S. cases — a fatality rate of 2/100 of one percent.
- COVID-19 is (thus far) more lethal than the two earlier pandemics — 4.6 percent of the number of cases reached 5 days earlier. (A 5-day lag yields the strongest correlation between new cases and new deaths.)
Rounding up to 5 percent — and assuming that the rate remains constant — a total of 100,000 deaths means a total of 2 million cases, and a total of 240,000 deaths means a total of 4.8 million cases. As of today, the number of cases is somewhere above 200,000. Will the number of cases increase 10-fold to 24-fold, or more? Will the fatality rate rise?
Lacking detailed knowledge of how the official estimates are derived, I computed non-linear estimates of the rates at which new cases and new deaths will occur, based on statistics through
March 31, 2020 (though numbers for Washington haven’t been posted for three days) April 1, 2020. The rate of increase in new cases declines gradually (the function is a decaying exponential) and never reaches zero, but approaches it by the end of June 2020. The rate at which new cases yield new deaths declines gradually, from a base of 5.8 6.6 percent, as the number of new cases increases (the relationship is a power function with an exponent of less than 1).
The bottom line: By July 1, 2020, the total number of cases in the U.S.
will may reach 800,000 870,000, resulting in 35,000 40,000 deaths. That’s a fatality rate of about 4.3 4.6 percent per case and 1/100 12/1,000 of 1 percent of the country’s population.
Again, I assume that lockdowns, quarantines, and social distancing continue (though for how long I can’t say). I also assume that there won’t be a second wave of COVID-19 because of re-infections or an early relaxation of precautions.
Why is my revised and more sophisticated estimate of the number of deaths so much lower than the official one? It’s probably true that the official estimate simulates the spread of the contagion, whereas my general model doesn’t do that. But my guess is that the official estimate has been inflated to scare people into staying at home, which will reduce the rate at which new cases arise and prevent the number of deaths from reaching 100,000 or more.