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Message: <blockquote data-quote="Celebrim" data-source="post: 7942729" data-attributes="member: 4937">So, let's look at today's numbers for South Korea.They have 8162 cases, of which only 76 have died. That makes for a transient case fatality ratio of 0.9%. (Notice that it has climbed by 0.3% since the article you quoted. This is not unexpected, and I think you'll soon see why.)So how do we know that it will converge (or in this case climb) to 3.4%?Well, so far of the 8162 cases, 834 people have recovered and are free from the illness. That means that there are 834 + 76 closed cases, or 910 cases that are complete. Of those 910 cases that are complete, 8.3% have died. That 8.3% number is the current mortality rate in South Korea. Recall that I told you that at the time the CFR was 0.6% the mortality rate was actually a scary sounding 24%. But it's decline down to at present 8.3% is also not unexpected.What is going on here?Well, there are 7253 cases of people that have neither gotten well nor died. Some of those people will get better, and some of them will die. When all the cases are closed, we'll know the final mortality rate - predicted to be around 3.4%. The two numbers are converging toward some number between them, and the reason they have the particular pattern they do is that this disease takes longer to recover from on average than it does to kill you. It usually takes 20-40 days to recover. But it usually only takes 12-17 days to die. So deaths tend to be front loaded resulting in a high mortality rate in the early going (governed by a ratio of deaths to recoveries). But transient case fatality ratios tend to be very low if you are finding the cases quickly, because the deaths lag symptoms by such a long length of time.Oh no, it is MUCH worse if you do nothing.  The highest observed rates have been around 5.9% in Wuhan itself where the medical system all but collapsed and they were forced to provide only triage to the most ill patients.   In theory, if you could do nothing at all, the mortality rate could be much higher than that.   About 10% of patients get very very ill and have to be on oxygen for 2-4 weeks.  That's why the talk about ventilators is so important and everyone is talking about "flattening the curve".(Now, all that said there are some weird data sets out there that seem to show you can get significantly below 3.4% mortality rate, though I don't think South Korea is necessarily one of them.  However, the two data sets that I know of that suggest that have some huge problems.)</blockquote>

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