This is an edited response to a COVID-19 misinformer I wrote on Facebook earlier tonight. She claimed that the fatality rate for COVID-19 was only 0.0001, and I called her out on it.

I don’t know where you got that fatality rate [of 0.0001], but it is very clearly wrong. You or whomever did the calculation did it incorrectly (or it’s a hell of typo).

Per the CDC, fatality rate (or more specifically, case-fatality rate) is the number of deaths due to a particular condition divided by the total number of people who have that condition. In this case that would be the total number of deaths from COVID-19 divided by the number of people who have been infected. In mathematical terms, that would be the following equation:

$CFR=\frac{Deaths\:due\:to\:COVID19}{Total\:Cases\:of\:COVID19}$

Per the link you provided, 130,133 people have died from COVID-19 thus far, so we know the # of COVID deaths. You claim the CFR is 0.0001, or one death for every 10000 cases. If we rearrange the equation to solve for the unknown (Total # of COVID cases), we get the following:

$Total\:Cases\:of\:COVID19=\frac{Deaths\:due\:to\:COVID19}{0.0001}$

Or, more simply, we can multiply the # of COVID deaths by 10,000. 130,133 * 10,000 is 1,301,330,000. That’s 1.30 billion people in the US alone who would have to have been infected for this many deaths to have occurred.

Except the population of the US was only 328.2 million in 2019, about 4.0 times less than the number of cases needed to produce your death rate.

Let’s assume it was a typo and you added a zero – the real fatality rate should have been 0.001. That would mean the total number of cases would have to be 130 million people. That’s about 40% of the entire country. Possible, but extremely unlikely given epidemiological studies suggest that we’re undercounting cases by 5-10x (and more likely closer to the 5x).

The CDC also counts the number of COVID cases, and we’re at about 3 million today [7/7/2020]. If we’re off by 5x, that means we could actually have had as many as 15 million cases, of which 12 million we didn’t count. But let’s assume that the lower estimate of the undercount is wrong – that we’ve actually had 30 million cases in the US. What would the death rate be then?

$\frac{130,133\:deaths\:from\:COVID19}{30\:million\:cases}=0.0043$

That’s 43 times the fatality rate you claim.

If we compare COVID-19 deaths to US influenza and pneumonia deaths, we see that COVID-19 has already killed more than double the number of people in the US as influenza and pneumonia combined did in 2017 (per this link). And we’re at the midpoint of the year, we never properly squelched the first wave, never mind a likely second wave this fall. We’ll be lucky if the deaths only double by the end of December given the way things are going right now.

And if they only double, that will make COVID-19 the third most lethal condition in 2020 behind only heart disease and the sum total of all cancers.

You are wrong, or the source of that number is wrong and you didn’t bother to sanity check it. Either way your error is propagating misinformation that is destroying lives and killing people. Please stop.