It’s not the mortality rate, stupid!

From the leader of the Free World to the world press to more than one researcher, there has been a focus on something called the mortality rate of the new viral disease, COVID-192. We are told that whether we should worry or not worry depends on whether the new(ish)3 infection does or does not cause many more deaths than traditional infections like the flu, a number apparently to be arrived at by dividing the number of fatalities by the number of infected (or ill or diagnosed) people. If this number is comparable to the flu, then we are supposed to take a break from worrying. On the other hand, if it is significantly higher, then we should go back to worrying. Or instead of flu, we are told to think of the number of people who die in car crashes divided by the total number of people driving or riding in an automobile. These are the supposedly key numbers we heard and read about when the question of locking down arose in the past couple of months. They are now red-hot again as the issue of what to do next (for example, relax the lock-down or maybe make it stricter?) becomes urgent.