You can't take a case into account until you know its outcome. What am I missing?
0. https://medical-dictionary.thefreedictionary.com/lethality+r...
The correct way to calculate A's case fatality rate would be to select a cohort, Group B, for example: everyone infected in the first week. And calculate:
(deaths in Group B by Feb 9th) / (deaths in Group B by Feb 9th + recovered in Group B by Feb 9th)
An incorrect way to calculate A's case fatality rate would be:
(deaths by Feb 9th) / (deaths by Feb 9th + recovered by Feb 9th)
This is incorrect because "deaths by Feb 9th" includes all deaths from people infected between Jan 1st and Feb 2nd, while "recovered by Feb 9th" only counts the recovered patients who were infected between Jan 1st and Jan 9th. The above equation basically expands to:
(deaths in Group C by Feb 9th) / (deaths in Group C by Feb 9th + recovered in Group D by Feb 9th)
Where:
Group C: infected between Jan 1st and Feb 2nd
Group D: infected between Jan 1st and Jan 9th
Since disease A is spreading exponentially, it's clear that Group C is a few orders of magnitude larger than Group D.
No idea where you got that 30% from. Even in Wuhan, with its medical infrastructure close to the breaking point, we are talking about 4.9%.
31,211 confirmed cases and 637 deaths in China. Makes a rate of roughly 2.04%. And I trust the WHO to get the calculation behind that right.
Another stat is that there are roughly 700 deaths and 2400 recoveries, which would indicate a mortality rate of 23%. Of course, this suffers from the same delay issue as the 2% calculation (T_death < T_recovery). But the possible range is 2% < M_rate < 23%
This paper gives a discussion of different biases:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4504518/
There's a standard paper on this topic the authors I forget atm but all estimates will be biased. The best estimates are sort of unintuitive and account for estimated time-to-death and the time since diagnosis.
According to https://coronavirus.app/ we have 34955 infected, 726 dead, 2287 recovered as of now. Total resolved cases are dead + recovered, which is 3013. Fatality rate is 726 / 3013 = 24.1%. At the time of my original post it was 30%.