How 2 Million American Lives Were Saved

It was predicted early in the year that COVID-19 could kill as many as 2.2 million Americans. A variety of other models showed between 1 and 2 million fatalities, and they received frontpage news coverage for days and weeks. But 9 months into this pandemic, we haven’t witnessed it.

Is the answer to this question, as some cult-like thought circles espouse, that COVID-19 kills ‘virtually’ nobody? Or perhaps that medical professionals intentionally inflate or even encourage COVID deaths? No. If you think that, clear it from your mind entirely.

The real answer is the compound growth effect— and more specifically, how protective measures affect rates of spread.

Infectious diseases reproduce in an exponential fashion due to the fact that each additional infected person is contagious. If on average each person infected with pathogen X spreads it to 1.5 persons over the course of their illness, which for the sake of argument, is one week, than the reproduction rate (R0) of the illness is 1.5, or a compound annual growth rate of 50 percent per week.

With this rate of reproduction of the virus, the number of cases grows from 1 to 130 over the span of twelve weeks. If the population afflicted were to have immediately taken protective measures, varying in efficacy, but reducing the mean reproduction rate to 1.3 (a two-fifths reduction in the rate of spread), the number of cases would have only been 23— that is to say, a 40 percent reduction in rate of spread resulted in 82 percent fewer cases. A four-fifths reduction in rate of spread would have resulted in 98 percent fewer cases.

Two put things in better perspective, 82 and 98 percent fewer cases is approximately one-fifth and one-fortieth the number of cases, respectively. This is a demonstration of a simple mathematical fact… that linear changes to compound growth rates have exponential effects.

Chart from my Google Spreadsheet demonstration of this effect, which can be found here.

That being said, an important idea is proven as a result. The first is that protective measures are effective on the aggregate— even if a cotton mask reduces the rate of spread by only 5 percent, and the unmitigated reproduction rate is 2, the reduction in case numbers and thus fatalities over ten compounding periods is 22 percent. Over twenty compounding periods (say, a year or so), the reduction is 40 percent.

We can stop the spread of the virus, and it wasn’t necessary, frankly, to trot out this short essay demonstration when in fact we can observe the effects of public health vigilance in large, densely populated countries such as Japan and Taiwan.

The virus can be starved of hosts in a month’s long totalitarian shut down. Or the spread curve can be flattened as to reduce the burden on hospitals, save and prolong lives, and delay major spread until the adoption of an effective vaccine or inoculant. So no, COVID is not ‘inevitable’ or ‘unstoppable’ and not everyone has to get it for this pandemic to end.

Main photo source. No changes made.

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