[nicolapede]

Given that it can take N weeks to die, wouldn't it make sense to calculate the mortality rate at a given time t as the number of deaths at time t divided by the number of reported infected people at time t-Nweeks ? (I am using N =3 for my back-of-the-envelope calculations).

[SpicyLemonZest]

No, since not everyone who dies will have had a confirmed case 3 weeks back - both because the actual time the disease takes is (almost surely) variable and because detection isn't perfect. The mortality rate in Iran is infinity by that metric, for example.