## LESSWRONGLW

The Diamond Princess cohort has 705 positive cases, of which 4 are dead and 36 serious or critical. In China, the reported ratio of serious/critical cases to deaths is about 10:1, so figure there will be 3.6 more deaths. From this we can estimate a case fatality rate of 7.6/705 ~= 1%. Adjust upward to account for cases that have not yet progressed from detection to serious, and downward to account for the fact that the demographics of cruise ships skew older. There are unlikely to be any undetected cases in this cohort.

5steve21523moHang on, maybe I'm being stupid, but I don't get the 3.6. Why not say 36+4=40 serious/critical cases and the 10%=4 of them have already passed away?

You're right, adding deaths+.1*serious the way I did seems incorrect. But, since not all of the serious cases have recovered yet, that would seem to imply that the serious:deaths ratio is worse in the Diamond Princess than it is in China, which would be pretty strange. It's not clear to me that the number of serious cases is as up to date as the number of positive tests.

So, widen the error bars some more I guess?

4Dagon3moHow many passengers were exposed? Capacity of 2670, I haven't seen (and haven't looked that hard) how many actual passengers and crew were aboard when the quarantine started. So maybe over 1/4 of exposed became positive, 6% of that positive become serious, and 10% of that fatal. Assuming it escapes quarantine and most of us are exposed at some point, that leads to an estimate of 0.0015 (call it 1/6 of 1%) of fatality. Recent annual deaths are 7.7 per 1000, so best guess is this adds 20%, assuming all deaths happen in the first year and any mitigations we come up with don't change the rate by much. I don't want to downplay 11.5 million deaths, but I also don't want to overreact (and in fact, I don't know how to overreact usefully). I'd love to know how many of the serious cases have remaining disability. Duration and impact of survival cases could easily be the differences between unpleasantness and disruption that doubles the death rate, and societal collapse that kills 10x or more as the disease directly.