As we have discussed in these pages, the CFR (case fatality rate) for COVID-19 is extremely difficult to calculate. We have a rough estimate of the numerator (deaths). But even that may be off, because of the difference between dying “with” COVID-19 and dying “of” COVID-19. In other words, if a person who was going to die of cancer today anyway gets COVID-19 an hour before he dies, is it correct to say he died of the virus just because he had it when he died. This is not theoretical. The Health Minister of Italy said the virus fatality number in his country is certainly overstated for this reason.
For all the problems the numerator has, they pale in comparison to the denominator. I think it is fair to say that any estimate of the actual number of cases out there borders on wild speculation, no matter the good faith and expertise of the researcher making the calculations. We know that “cases presenting for treatment” would be way too low, because most cases don’t present for treatment. We know that “all those that test positive” is too low, because the rate of testing is both uneven geographically and limited numerically for logistical reasons.
Now we have this study out of Stanford to really throw a monkey wrench into the calculations. Very briefly, they tested a large sample of people in an attempt to get a handle on the incidence of the virus in the wild. It turns out that way more people had the virus and did not even know it that was previously thought. Read the study. But here’s the bottom line: The denominator may be understated by a factor of up to 85.
So, if the previous estimate of the CFR was 2%, the actual CFR may be 2% divided by 85.