There remains substantial uncertainty about the dynamic of the COVID-19 pandemic. Some of this uncertainty is related to the novelty of the virus, and some is related to lags in testing, such as in the U.S.
The latter implies that the recent increase in the number of confirmed cases in the U.S.—which doubled between March 23 and March 26—reflects the spread of the virus as well as the increasing intensity of the testing campaign. As we noted in a previous blog post “COVID-19 and the Importance of Testing,” the number of confirmed cases alone is not sufficient to understand the scope of the pandemic. In this post, we document COVID-19-related deaths (instead of confirmed cases) in a few countries and use those data to provide projections for the U.S.
The figure below shows COVID-19-related deaths per 10 million people for a few countries, as of March 26. Day 1 is the day when that country’s COVID-19-related death rate reached 1 per 10 million people.
Mortality in Spain and Italy are orders of magnitude higher than in China and South Korea. By Day 10, the death-to-population ratio in Italy was more than 3 times that of China or South Korea. For Spain, it was even higher.
We used the figure above to build projections for the U.S. for two extreme scenarios: South Korea and Italy/Spain. Our thought experiment is as follows: What would the number of COVID-19-related deaths in the U.S. be in the coming days (that is, from Day 15 onward) if the death-to-population ratio was the same as in South Korea or Italy from their Day 15 onward? (Recall that because both South Korea and Italy had their first death earlier than the U.S., their Day 15 has already passed.)
Consider the U.S. on Day 14, which would be March 24. A total of 706 people had died by then. With the U.S. population at 327 million, the number of deaths was 22 per 10 million people. The figure below projects COVID-19-related deaths in the U.S. if the country experiences similar death-to-population ratios as a few other countries.
Day 14 in South Korea was March 7, and the death-to-population ratio was 8.6 per 10 million people on that day. In the U.S., this ratio would represent 282 deaths. Thus, under the South Korea scenario, the U.S. would have seen 282 deaths by March 24. Going forward, the death-to-population ratio in South Korea on Day 15 was 9.8. When applied to the U.S. population, it would represent 321 deaths.
Similarly, Day 14 in Italy was March 8, and the death-to-population ratio on this day was 61. Applying this ratio to the U.S. would yield 1,995 deaths.
The South Korea scenario implies the least number of deaths in the United States, 22 deaths per 10 million by April 8, or 712 total deaths. (The South Korea scenario is unrealistic since the U.S. has more deaths already.) The Italy and Spain scenarios imply a large and fast growing number of deaths. In the projection based on Italy, the total number of deaths by April 8 would be 37,169.
1 As we noted in a previous blog post “COVID-19 and the Importance of Testing,” the number of confirmed cases alone is not sufficient to understand the scope of the pandemic.