### Part of the Covid Mortality Puzzle

We would like to know the mortality rate, the percentage of people who get the disease who die as a result. That requires two numbers: number infected and number dead as a result.

The best estimates of number infected come from seroprevalence studies, testing a random sample of people for evidence that they have had the disease. There has been a good deal of discussion of the results, which generally indicate a much larger number, up to ten times as large, as the number of recorded cases.

I have not seen a careful discussion of problems with the other number. Under current circumstances, I think it unlikely that many deaths in developed countries will be missed, since the symptoms that suggest Covid are obvious and tests available. But we might err in the other direction, by counting deaths due to other causes but occurring to people infected with Covid. As a number of people have pointed out hospitals have a financial incentive to classify a death whose cause is ambiguous as due to Covid.

How large could that effect be?

I start with a high value of number infected in the U.S. — ten times the number of known cases, or 28 million. Assume, for simplicity, that those infections were spread out evenly over a period of four months and that each would test positive for a month. Then the number who would test positive at any given time was 7 million, or about 2% of the population.

I start with a high value of number infected in the U.S. — ten times the number of known cases, or 28 million. Assume, for simplicity, that those infections were spread out evenly over a period of four months and that each would test positive for a month. Then the number who would test positive at any given time was 7 million, or about 2% of the population.

The U.S. mortality rate from all causes is 2,813,503 per year. I want to know how many of those would have died from causes other than Covid, over a four month period, while infected, so I multiply by .02 for number infected, divide by 3 for a third of a year of mortality. The result comes to about 19,000.

That should be an upper bound on by how much we are overcounting covid mortality by classifying deaths of people infected with Covid but due to other causes as due to Covid. The current count for total deaths in the U.S. due to Covid is 131,000. Assuming I haven't made any mistakes in my very rough calculation, that might be too high, but not by very much.

Readers are welcome to point out errors in either the logic or the numbers I am using, remembering that what I am looking for is an upper bound on the overcount.