I also thought that in Lombardia, the estimates given by Ioannidis are rapidly trending toward coming in contradiction with SIR models. :( Lombardia has a population of 11 million people and 2,500 reported deaths. Some doctors are raising alarm that many deaths are going undetected because people are dying at a rate that’s 4 times higher than the same month last year. In addition, the death counts always lags behind because some people are sick for a long time before they die (though maybe this start to be the case less strongly in conditions of extreme hospital overstrain). All of this suggests that an estimate of 10,000 deaths for Lombardia alone might soon prove to be accurate. But according to the IFR provided by Ioannidis, this would correspond to an expected 8 million people infected (72% of the population). I don’t understand SIR models well enough to calculate what the R0 would have to be for 72% of a population to get infected. I suspect that Covid-19′s R0 is high enough to be consistent with this, but it wouldn’t leave a lot of room for estimation errors.
That said, I think the above calculation is naive, so the argument doesn’t work (at least not in this crude form). If hospitals become as overwhelmed as they are in Italy, I’m sure that even someone with Ioannidis’ view would expect the IFR for Lombardy to become a lot higher than 0.125% because a lot of people aren’t getting life-saving hospital attention.
So, this means that Lombardy isn’t necessarily a knockdown argument against Ioannidis’s estimate in the same way South Korea is. However, I think Ioannidis’s estimate would have counterintuitive implications for the percentage of people infected in Lombardy. It would have to be in the double digits already at the very least. The most trustworthy estimate I saw about Wuhan suggested that only 5% of its population had the virus. However, there’s some disagreement about this, and the people who tend to argue for an unusually low IFR also tend to argue that there’s a giant iceberg of undetected asymptomatic cases.
UPDATE: I just realized something: I read somewhere recently that Italy is doing 30,000 tests a day by now, and that about 25% of them are positive. This seems to be in contradiction with Ioannidis’s estimate because his view should imply that, if there’s some kind of selection at all for who they are testing (as opposed to just testing members of the population at random), then we should expect to see more positive test results than 25%. (Why? Because if we assume that hospital overstrain increases his death rate estimate by a factor of 7x (which is a really large adjustment!), the death count estimates for Lombardy combined with Ioannidis’s estimates would still suggest that above 10% of the population would have the virus. Such high numbers would only be consistent with reality if most people had relatively mild symptoms or no symptoms at all, so assuming that there’s substantial pre-selection on who is getting tested (as opposed to random testing, which would be odd), a rate of 25% positive tests would be implausibly low for the scenario where >10% of the region were infected. So, to conclude, I think one can plausibly construct a case against Ioannidis’s estimates based solely on common sense and numbers from Lombardia. I probably haven’t quite succeeded at making this case in a watertight way, but I think you might be right with your intuition. This is just one more reason why the 0.125% estimate is completely absurd.
I also thought that in Lombardia, the estimates given by Ioannidis are rapidly trending toward coming in contradiction with SIR models. :( Lombardia has a population of 11 million people and 2,500 reported deaths. Some doctors are raising alarm that many deaths are going undetected because people are dying at a rate that’s 4 times higher than the same month last year. In addition, the death counts always lags behind because some people are sick for a long time before they die (though maybe this start to be the case less strongly in conditions of extreme hospital overstrain). All of this suggests that an estimate of 10,000 deaths for Lombardia alone might soon prove to be accurate. But according to the IFR provided by Ioannidis, this would correspond to an expected 8 million people infected (72% of the population). I don’t understand SIR models well enough to calculate what the R0 would have to be for 72% of a population to get infected. I suspect that Covid-19′s R0 is high enough to be consistent with this, but it wouldn’t leave a lot of room for estimation errors.
That said, I think the above calculation is naive, so the argument doesn’t work (at least not in this crude form). If hospitals become as overwhelmed as they are in Italy, I’m sure that even someone with Ioannidis’ view would expect the IFR for Lombardy to become a lot higher than 0.125% because a lot of people aren’t getting life-saving hospital attention.
So, this means that Lombardy isn’t necessarily a knockdown argument against Ioannidis’s estimate in the same way South Korea is. However, I think Ioannidis’s estimate would have counterintuitive implications for the percentage of people infected in Lombardy. It would have to be in the double digits already at the very least. The most trustworthy estimate I saw about Wuhan suggested that only 5% of its population had the virus. However, there’s some disagreement about this, and the people who tend to argue for an unusually low IFR also tend to argue that there’s a giant iceberg of undetected asymptomatic cases.
UPDATE: I just realized something: I read somewhere recently that Italy is doing 30,000 tests a day by now, and that about 25% of them are positive. This seems to be in contradiction with Ioannidis’s estimate because his view should imply that, if there’s some kind of selection at all for who they are testing (as opposed to just testing members of the population at random), then we should expect to see more positive test results than 25%. (Why? Because if we assume that hospital overstrain increases his death rate estimate by a factor of 7x (which is a really large adjustment!), the death count estimates for Lombardy combined with Ioannidis’s estimates would still suggest that above 10% of the population would have the virus. Such high numbers would only be consistent with reality if most people had relatively mild symptoms or no symptoms at all, so assuming that there’s substantial pre-selection on who is getting tested (as opposed to random testing, which would be odd), a rate of 25% positive tests would be implausibly low for the scenario where >10% of the region were infected. So, to conclude, I think one can plausibly construct a case against Ioannidis’s estimates based solely on common sense and numbers from Lombardia. I probably haven’t quite succeeded at making this case in a watertight way, but I think you might be right with your intuition. This is just one more reason why the 0.125% estimate is completely absurd.