Relying on data collected through April 5, I project about 920,000 cases and 54,000 deaths by the end of June. Figure 1 plots the projections by date. It is reassuring to see that the curve for cases resembles a Gompertz function, which is a classic descriptor of the growth of pandemics.
Notes about data: I use official statistics reported by States and the District of Columbia and compiled in Template:2019–20 coronavirus pandemic data/United States medical cases at Wikipedia. The statistics exclude cases and deaths occurring among repatriated persons (i.e., Americans returned from other countries or cruise ships). The source tables include the U.S. territories of Guam, the Northern Mariana Islands, Puerto Rico, and the Virgin Islands, but I have excluded them from my analysis. I would also exclude Alaska and Hawaii, given their distance from the coterminous U.S., but it would be cumbersome to do so. Further, both States have low numbers of cases and thus far only 10 deaths (6 in Alaska and 4 in Hawaii), so leaving them in has almost no effect on my analysis.
My method of projecting COVID-19 cases and deaths yields far fewer deaths than the official estimate issued by the White House: 100,000 to 240,000. 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.
RELATED CHARTS AND ANALYSIS
As indicated by Figure 2, the number of cases is 1/10th of 1 percent of the population of the U.S.; the number of deaths, 3/100th of 1 percent. Thus far 2.9 percent of cases have resulted in deaths, but the final fatality rate will be higher because new deaths lag new cases (as discussed later). Note the logarithmic scale on the vertical axis; every major division (e.g., 0.01%) is 10 times the preceding major division (e.g., 0.001%).
Figure 3 shows how the coronavirus outbreak compares with earlier pandemics when the numbers for those pandemics are adjusted upward to account for population growth since their occurrence. (Again, note that the vertical axis is logarithmic.) Thus far, the number of COVID-19 cases is only 1/2 of 1 percent of the number of swine-flu cases, but the number of COVID-19 deaths has reached 3/4 the number of swine-flu deaths. In the end, the U.S. fatality rate for the swine-flu pandemic was 2/100 of 1 percent; for the Spanish flu pandemic, 2 percent. The rate for the COVID-19 pandemic probably will be the highest of the three, but the the true toll won’t be known until there is a solid estimate of the number of deaths over and above the number that would have occurred normally during the period of COVID-19 outbreak in the U.S. (See this post by Dr. Roy Spencer.) Whatever the final toll, it will prove to be lower than the official tallies now in circulation, and thus lower than my projection.
As shown in Figure 4, the daily percentage changes in new cases and deaths have been declining generally since March 19. However, actual numbers of new cases and deaths probably won’t begin to drop for another several days.
New deaths necessarily lag new cases. The best fit between new cases and new deaths is a 6-day lag (Figure 5).
Figure 6 shows the tighter relationship between new cases and new deaths (especially in the past two weeks) when Figure 4 is adjusted to introduce the 6-day lag.
Figure 7 shows the similarly tight relationship that results from the removal of the 6 “hot spots” — Connecticut, Louisiana, Massachusetts, Michigan, New Jersey, and New York — which have the highest incidence of cases per capita.
Figures 6 and 7 give me added confidence that the crisis is about to reach its peak and begin to subside. Fingers crossed.