One Hundred Twenty Million Deaths?

Could two billion people die from COVID-19? It’s not likely, but according to a recent statistical study of 71 historical contagious disease epidemics by Pasquale Cirillo and Nassim Taleb, there have been two historical epidemics that when adjusted to the current world population, would be the current equivalent of more than two billion deaths. Both were outbreaks of the plague.

The first was the Plague of Justinian that took place over a period of 8 years beginning in 541 AD. It affected Europe, the Middle East, and other countries that border the Mediterranean. This outbreak of the plague is estimated to have killed between 25 and 100 million people at a time when the population of the known world was 200 million people. Re-sized for today’s population, that is 900 million – 3.6 billion. The middle of this range is approximately 2.2 billion.

The second was another outbreak of the plague that occurred from 1331 to 1353. Known as the Black Death, it killed between 75 and 200 million people throughout Europe, Northern Africa, the Middle East, and Central Asia at a time when the known world’s population was less than 400 million. Scaling up an average estimate of the number of deaths to today’s population, it is the equivalent of 2.7 billion deaths in today’s world.

Hopefully COVID-19 won’t result in billion of deaths, but examples like these show just how bad a pandemic can be. As of July 13, 2020, COVID-19 is estimated to have resulted in 578,000 deaths worldwide, including 139,000 deaths in the United States. Taken in an historical context, half a million deaths is slightly less than the median for all 71 data points in Cirillo and Taleb’s study, which only included epidemics that resulted in at least 1,000 deaths.

Not only have there been 578,000 deaths, but there is currently no end in sight. Progress is being made on a vaccine by several groups, but on July 13th there were 3,719 deaths worldwide and 465 in the United States. How many more are likely? Taking into account the fact that there have been 577,000 deaths worldwide and using the statistical methods that Cirillo and Taleb present in their paper, the average total expected is 120 million. If the proportion of U.S. deaths continues to stay at 25% of the world total, that is 30 million deaths in the United States due to COVID-19. Note that this is a very simple analysis that does not take into account the possibility of a vaccine, does not considers the impact of therapeutic measures to reduce the mortality rate, and does not consider the impact of social distancing, mask wearing, or other preventive measures.

Another way to estimate the possible number of eventual deaths in the U.S. due to COVID-19 is to use an historical analogy, such as the Spanish flu epidemic of 1918-1920. This severe flu outbreak killed 0.6% of the U.S. population. Taken as a percent of today’s population, that is about 2 million people. That is more than 10 times the current number of deaths, but a real possibility.

Recently, epidemiologists at Columbia University estimated the fatality rate due to the COVID-19 outbreak in New York City this past Spring. In their study, they estimated the infection mortality rate to be 1.45%. If every person in the U.S. were to contract the disease, that could mean as many as 5 million deaths due to COVID-19.

Due to the extreme amount of variation in the historical data, an accurate forecast is difficult, and this is not analysis meant to be a forecast. Phenomena like epidemics are subject to such extreme variation that it is almost impossible to accurately forecast them more than a few weeks out. Rather, this kind of analysis is something that we should keep in mind as we prepare to send students back to school this fall and as we venture out into the world. Looking at these extreme risks, known as tail risks, is something commonly done by casualty insurance companies that are exposed to potentially tremendous liabilities due to natural disasters such as hurricanes and earthquakes. Until a vaccine is developed, we are exposed to the tremendous risk of COVID-19 and we need to do everything we can to guard against this possibility.

Wearing masks, for example, is a cheap, effective action we can all take. Japan has had less than 1,000 deaths and is more densely populated than the United States. However, they never shut down their economy. Instead, they have been universally wearing masks for several months. Without more risk mitigation or a vaccine in the near future, millions of deaths from COVID-19 in the U.S. could occur.