As I write this, on March 29, 2020, according to the World Health Organization, there have been 634,835 confirmed cases of Covid-19, the disease caused by the SARS-CoV-2 virus, leading to 29,891 deaths. In the USA, there have been 103,321 confirmed cases and 1,668 deaths. In the coming weeks, even with the quarantines and shelter-in-place orders—the effects of which will take weeks to be seen—these figures are going to look tiny.
Since worldwide testing has tended to have been directed at those with severe symptoms, it’s not known with great accuracy what the true mortality rate is, that’s the rate that people who become infected with the SARS-CoCV-2 virus end up dying from the infection. However, a reasonable estimate now places it somewhere between 0.5 and 1%. Some estimates are even lower than 0.5%.
Our measurement of the number of people who have died is clearly much more accurate than our measurement of the number of people who have been infected. With the lowest estimated mortality rate of 0.5%, we can generate a potentially more accurate assessment of the number current infections: 5,978,200 worldwide (almost ten times the confirmed number) and 333,600 in the USA (over three times the confirmed number).
You might protest that 0.5% is underestimating the mortality rate. Okay, so let’s use the estimated upper bound of 1%. That yields 2,989,100 infections worldwide (almost five times the confirmed number) and 166,800 infections in the USA (1.6 times the confirmed number). Remember that these are reasonable estimates of the number of people who have been infected right now.
In the USA, the number of deaths has been doubling every four days. At this rate of exponential growth, without an intervention, in 28 days (on April 26, 2020), after seven doublings, the numbers, using the 0.5% mortality rate, will be 128 times larger (128 is 2⁷): 42,700,800 infected (13% of the population) and 213,504 dead.
If the medical system is overwhelmed, which it probably would be, then the average mortality rate would climb due to lack of treatment, including the lack of respirators. One percent of 42,700,800 infected is 427,008 dead.
The incubation period is around 5 days, and the time from showing symptoms to dying from the disease may be around 10 days. This means that the people who are dying today in the USA were probably infected before any shelter-in-place orders when into effect.
Some of the exponential growth will be limited by the fact that approximately half of the US population is now under shelter-in-place orders, but the effect of that will take a few weeks to become apparent as the death toll caused by the existing infections is revealed.
What I’m taking away from this analysis is a sobering reassessment of the critical importance of us all following the prescribed interventions: stay home, wash your hands, and don’t touch your face.
Check the CDC website for more information.
Read the follow-up here: