## Tuesday, January 28, 2020

### Estimating the mortality rate of CoV2019

The original news reports misidentified CoV2019 as SARS. That is understandable because they are both coronavirus.

SARS had 8098 documented cases and 774 documented fatalities for a mortality rate of approximately 10%. The mortality rate increased rapidly for people over fifty and was said to exceed 50% mortality for people over 60.

Compare that to a typical year of the seasonal flu. The seasonal flu might kill a half million people globally every year. If that mortality rate was extended to a population of 8089 then there is a flip-of-the-coin chance that one person would die. The other side of the coin is that nobody would die.

Very big difference between half-a-person and 774 people.

Let's extend the rate seasonal flu rate to 11 million, the population of Wuhan, China. In that case almost 800 people would die. That sounds like a lot of people but consider that an average of 400 people die every 24 hours in a population of 11 million and the fatalities due to the seasonal flu are spread over three months.

Other factors that dilute the impact of deaths from the seasonal flu is that many of those people die three weeks after getting the flu due to secondary complications like pneumonia and many of those who die due to the seasonal flu are already in frail health and the flu was the last straw.

The videos coming out of Wuhan suggest that CoV2019 is striking down otherwise healthy people. It is dropping them like a bolt-from-the-blue.

One of the difficulties in getting a handle on the mortality rate of a rapidly growing epidemic is that one cannot simply divide the number of dead by the number of patients.

The reason is that the population of patients includes the person diagnosed yesterday and we won't know if he "survived" for about forty days* due to complications and secondary infections.

So it is impossible to calculate a fatality rate until
-You have solid, not politically tainted counts
-You have enough history to estimate the mortality curve. That is, "50% of the fatalities occur in the first 16 days after diagnosis" kind of information.
-You have enough history so you can take a snap-shot of a cohort of patients and then count how many are still alive sixteen days later.

The bottom line is that it is way too soon to quantify the fatality rate of CoV2019 but anecdotal evidence is that it is at least ten times higher than seasonal flu and may be a thousand times higher than that. Time will tell.

*I want to embellish the "forty day" number. Suppose one of the complications of this virus is renal (kidney) failure. The disease loads the blood with the cellular trash. They lodge in the kidneys. The cellular flotsam is saturated with viral fingerprints. The immune system goes nuts and nukes the kidneys as collateral damage.

If that happened today, the patient would be put on dialysis three times a week and could live for twenty years.

If that were even a slightly common side effect to CoV2019, then there are not enough dialysis machines and people start dying from renal failure weeks after they were "cured" of CoV2019.

That is just ONE possible wave of delayed mortality.