Just for the record, I think that this estimate is pretty high and I’d be pretty surprised if it were true; I’ve talked to a few biosecurity friends about this and they thought it was too high. I’m worried that this answer has been highly upvoted but there are lots of people who think it’s wrong. I’d be excited for more commenters giving their bottom line predictions about this, so that it’s easier to see the spread.
Wei_Dai, are you open to betting about this? It seems really important for us to have well-calibrated beliefs about this.
Yeah, I kind of wrote that in a hurry to highlight the implications of one particular update that I made (namely that if hospitals are overwhelmed the CFR will become much higher), and didn’t mean to sound very confident or have it be taken as the LW consensus. (Maybe some people also upvoted it for the update rather than for the bottom line prediction?)
I do still stand by it in the sense that I think there’s >50% chance that global death rate will be >2.5%. Instead of betting about it though, maybe you could try to convince me otherwise? E.g., what’s the weakest part of my argument/model, or what’s your prediction and how did you arrive at it?
Epistemic status: I don’t really know what I’m talking about. I am not at all an expert here (though I have been talking to some of my more expert friends about this).
EDIT: I now have a Guesstimate model here, but its results don’t really make sense. I encourage others to make their own.
Here’s my model: To get such a large death toll, there would need to be lots of people who need oxygen all at once and who can’t get it. So we need to multiply the proportion of people who might have be infected all at once by the fatality rate for such people. I’m going to use point estimates here and note that they look way lower than yours; this should probably be a Guesstimate model.
Fatality rate
This comment suggests maybe 85% fatality of confirmed cases if they don’t have a ventilator, and 75% without oxygen. EDIT: This is totally wrong, see replies. I will fix it later. Idk what it does to the bottom line.
But there are plausibly way more mild cases than confirmed cases. In places with aggressive testing, like Diamond Princess and South Korea, you see much lower fatality rates, which suggests that lots of cases are mild and therefore don’t get confirmed. So plausibly there are 4x as many mild cases as confirmed cases. This gets us to like 3% fatality rate (again assuming no supplemental oxygen, which I don’t think is clear and I expect someone else to be able to make progress on forecasting if they want).
How many people get it at once
(If we assume that like 1000 people in the US currently have it, and doubling time is 5 days, then peak time is like 3 months away.)
To get to overall 2.5% fatality, you need more than 80% of living humans to get it, in a big clump such that they don’t have oxygen access. This probably won’t happen (20%), because of arguments like the following:
This doesn’t seem to have happened in China, so it seems possible to prevent.
China is probably unusually good at handling this, but even if only China does this
Flu is spread out over a few months, and it’s more transmissible than this, and not everyone gets it. (Maybe it’s because of immunity to flu from previous flus?)
If the fatality rate looks on the high end, people will try harder to not get it
Other factors that discount it
The warm weather might make it get a lot less bad. (10% hail mary?)
Effective countermeasures might be invented in the next few months. Eg we might need to notice that some existing antiviral is helpful. People are testing a bunch of these, and there are some that might be effective. (20% hail mary?)
Conclusion
This overall adds up to like 20% * (1-0.1-0.2) = 14% chance of 2.5% mortality, based on multiplications of point estimates which I’m sure are invalid.
In places with aggressive testing, like Diamond Princess and South Korea, you see much lower fatality rates, which suggests that lots of cases are mild.
With South Korea, I think most cases have not had enough time to progress to fatality yet. With Diamond Princess, there are 7 deaths out of 707 detected cases so far, with more than half of the cases still active. I’m not sure how you concluded from this “that lots of cases are mild”. Please explain more? That page does say only 35 serious or critical cases, but I suspect this is probably because the passengers are now spread all over the world and updates on them (e.g. progressing to serious or critical) are no longer being provided (unless someone dies).
So plausibly there are 4x as many mild cases as severe cases. This gets us to like 3% fatality rate (again assuming no supplemental oxygen, which I don’t think is clear and I expect someone else to be able to make progress on forecasting if they want).
Also don’t understand this part. “4x as many mild cases as severe cases” is compatible with what I assumed (10%-20% of all cases end up severe or critical) but where does 3% come from?
Update on Diamond Princess: as of now, Wikipedia says that the death toll is 14, or 2% of the passengers who tested positive within the first month. However, the dead all seem to have been elderly (there were many elderly passengers, as expected for a cruise liner). More specifically, 11 of them were over 70, another was over 60, and two others were of undisclosed age due to family wishes.
I don’t know how to adjust those results for demographics, and of course you can’t use them to predict what would happen without hospital care. But it’s a promising sign (relative to Wei’d predictions) that we’ve made it this far without anything obviously worse than what happened in Italy and Spain, and even those have seen far less than 0.1% of their population die. NYC is estimated to have a 20% rate of infection, and it too has had less than 0.1% of its population die (though this may rise somewhat, as their wave of cases crested fairly recently).
I’ve now made a Guesstimate here. I suspect that it is very bad and dumb; please make your own that is better than mine. I’m probably not going to fix problems with mine. Some people like Daniel Filan are confused by what my model means; I am like 50-50 on whether my model is really dumb or just confusing to read.
Also don’t understand this part. “4x as many mild cases as severe cases” is compatible with what I assumed (10%-20% of all cases end up severe or critical) but where does 3% come from?
Yeah my text was wrong here; I meant that I think you get 4x as many unnoticed infections as confirmed infections, then 10-20% of confirmed cases end up severe or critical.
For what it’s worth I don’t see why the guesstimate makes sense—it assumes that the only people who die are those who get the disease during oxygen shortages, which seems wrong to me. [EDIT: it’s possible that I’m confused about what the model means, the way to check this would be to see if I believe something false about it and then correct my belief]
My impression is that the WHO has been dividing up confirmed cases into mild/moderate (≈80%) and severe/critical (20%). The guesstimate model assumes that there are 80% “mild” cases, and 20% “confirmed” cases, which is inconsistent with WHO’s terminology. If you got the 80%-number from WHO or some other source using similar terminology, I’d recommend changing it. If you got it from a source explicitly talking about asymptomatic cases or so-mild-that-you-don’t-go-to-the-doctor, then it seems fine to keep it (but maybe change the name).
Edit: Wikipedia says that Diamond Princess had 392⁄705 asymptomatic cases by 26th February. Given that some of the patients might go on to develop symptoms later on, ≈55% might be an upper bound of asymptomatic cases?
Most people infected with COVID-19 virus have mild disease and recover. Approximately 80% of laboratory confirmed patients have had mild to moderate disease, which includes non-pneumonia and pneumonia cases, 13.8% have severe disease (...) and 6.1% are critical (...). Asymptomatic infection has been reported, but the majority of the relatively rare cases who are asymptomatic on the date of identification/report went on to develop disease. The proportion of truly asymptomatic infections is unclear but appears to be relatively rare and does not appear to be a major driver of transmission.
How much oxygen is there to go round? Why think that everyone getting sick in one month will exhaust supplies but not if everyone gets sick in six months? I’d guess that there is very little oxygen to go round.
Am I correct that you’re assuming a percentage chance of access to oxygen or a ventilator, rather than a cut off after which we run out of ventilators?
This comment suggests maybe 85% fatality of confirmed cases if they don’t have a ventilator, and 75% without oxygen.
I don’t understand how you get those kinds of numbers from the fb-comment, they’re way too high. Maybe you mean fatality of severe or critical cases, or survival rates rather than fatality rates. Do you mind clarifying?
Flu is spread out over a few months, and it’s more transmissible than this, and not everyone gets it. (Maybe it’s because of immunity to flu from previous flus?)
Are you saying that the flu is more transmissible than corona? I think I’ve read that corona is spreading faster, but I don’t have a good source, so I’d be curious if you do.
Just for the record, I think that this estimate is pretty high and I’d be pretty surprised if it were true; I’ve talked to a few biosecurity friends about this and they thought it was too high. I’m worried that this answer has been highly upvoted but there are lots of people who think it’s wrong. I’d be excited for more commenters giving their bottom line predictions about this, so that it’s easier to see the spread.
Wei_Dai, are you open to betting about this? It seems really important for us to have well-calibrated beliefs about this.
Yeah, I kind of wrote that in a hurry to highlight the implications of one particular update that I made (namely that if hospitals are overwhelmed the CFR will become much higher), and didn’t mean to sound very confident or have it be taken as the LW consensus. (Maybe some people also upvoted it for the update rather than for the bottom line prediction?)
I do still stand by it in the sense that I think there’s >50% chance that global death rate will be >2.5%. Instead of betting about it though, maybe you could try to convince me otherwise? E.g., what’s the weakest part of my argument/model, or what’s your prediction and how did you arrive at it?
Epistemic status: I don’t really know what I’m talking about. I am not at all an expert here (though I have been talking to some of my more expert friends about this).
EDIT: I now have a Guesstimate model here, but its results don’t really make sense. I encourage others to make their own.
Here’s my model: To get such a large death toll, there would need to be lots of people who need oxygen all at once and who can’t get it. So we need to multiply the proportion of people who might have be infected all at once by the fatality rate for such people. I’m going to use point estimates here and note that they look way lower than yours; this should probably be a Guesstimate model.
Fatality rate
This comment suggests maybe 85% fatality of confirmed cases if they don’t have a ventilator, and 75% without oxygen. EDIT: This is totally wrong, see replies. I will fix it later. Idk what it does to the bottom line.
But there are plausibly way more mild cases than confirmed cases. In places with aggressive testing, like Diamond Princess and South Korea, you see much lower fatality rates, which suggests that lots of cases are mild and therefore don’t get confirmed. So plausibly there are 4x as many mild cases as confirmed cases. This gets us to like 3% fatality rate (again assuming no supplemental oxygen, which I don’t think is clear and I expect someone else to be able to make progress on forecasting if they want).
How many people get it at once
(If we assume that like 1000 people in the US currently have it, and doubling time is 5 days, then peak time is like 3 months away.)
To get to overall 2.5% fatality, you need more than 80% of living humans to get it, in a big clump such that they don’t have oxygen access. This probably won’t happen (20%), because of arguments like the following:
This doesn’t seem to have happened in China, so it seems possible to prevent.
China is probably unusually good at handling this, but even if only China does this
Flu is spread out over a few months, and it’s more transmissible than this, and not everyone gets it. (Maybe it’s because of immunity to flu from previous flus?)
If the fatality rate looks on the high end, people will try harder to not get it
Other factors that discount it
The warm weather might make it get a lot less bad. (10% hail mary?)
Effective countermeasures might be invented in the next few months. Eg we might need to notice that some existing antiviral is helpful. People are testing a bunch of these, and there are some that might be effective. (20% hail mary?)
Conclusion
This overall adds up to like 20% * (1-0.1-0.2) = 14% chance of 2.5% mortality, based on multiplications of point estimates which I’m sure are invalid.
With South Korea, I think most cases have not had enough time to progress to fatality yet. With Diamond Princess, there are 7 deaths out of 707 detected cases so far, with more than half of the cases still active. I’m not sure how you concluded from this “that lots of cases are mild”. Please explain more? That page does say only 35 serious or critical cases, but I suspect this is probably because the passengers are now spread all over the world and updates on them (e.g. progressing to serious or critical) are no longer being provided (unless someone dies).
Also don’t understand this part. “4x as many mild cases as severe cases” is compatible with what I assumed (10%-20% of all cases end up severe or critical) but where does 3% come from?
Update on Diamond Princess: as of now, Wikipedia says that the death toll is 14, or 2% of the passengers who tested positive within the first month. However, the dead all seem to have been elderly (there were many elderly passengers, as expected for a cruise liner). More specifically, 11 of them were over 70, another was over 60, and two others were of undisclosed age due to family wishes.
I don’t know how to adjust those results for demographics, and of course you can’t use them to predict what would happen without hospital care. But it’s a promising sign (relative to Wei’d predictions) that we’ve made it this far without anything obviously worse than what happened in Italy and Spain, and even those have seen far less than 0.1% of their population die. NYC is estimated to have a 20% rate of infection, and it too has had less than 0.1% of its population die (though this may rise somewhat, as their wave of cases crested fairly recently).
I’ve now made a Guesstimate here. I suspect that it is very bad and dumb; please make your own that is better than mine. I’m probably not going to fix problems with mine. Some people like Daniel Filan are confused by what my model means; I am like 50-50 on whether my model is really dumb or just confusing to read.
Yeah my text was wrong here; I meant that I think you get 4x as many unnoticed infections as confirmed infections, then 10-20% of confirmed cases end up severe or critical.
For what it’s worth I don’t see why the guesstimate makes sense—it assumes that the only people who die are those who get the disease during oxygen shortages, which seems wrong to me. [EDIT: it’s possible that I’m confused about what the model means, the way to check this would be to see if I believe something false about it and then correct my belief]
My impression is that the WHO has been dividing up confirmed cases into mild/moderate (≈80%) and severe/critical (20%). The guesstimate model assumes that there are 80% “mild” cases, and 20% “confirmed” cases, which is inconsistent with WHO’s terminology. If you got the 80%-number from WHO or some other source using similar terminology, I’d recommend changing it. If you got it from a source explicitly talking about asymptomatic cases or so-mild-that-you-don’t-go-to-the-doctor, then it seems fine to keep it (but maybe change the name).
Edit: Wikipedia says that Diamond Princess had 392⁄705 asymptomatic cases by 26th February. Given that some of the patients might go on to develop symptoms later on, ≈55% might be an upper bound of asymptomatic cases?
Some relevant quotes from WHO-report (mostly to back up my claims about terminology; Howie questions the validity of the last sentences further down in this thread):
How much oxygen is there to go round? Why think that everyone getting sick in one month will exhaust supplies but not if everyone gets sick in six months? I’d guess that there is very little oxygen to go round.
Am I correct that you’re assuming a percentage chance of access to oxygen or a ventilator, rather than a cut off after which we run out of ventilators?
I don’t understand how you get those kinds of numbers from the fb-comment, they’re way too high. Maybe you mean fatality of severe or critical cases, or survival rates rather than fatality rates. Do you mind clarifying?
Are you saying that the flu is more transmissible than corona? I think I’ve read that corona is spreading faster, but I don’t have a good source, so I’d be curious if you do.
Oh yeah I’m totally wrong there. I don’t have time to correct this now. Some helpful onlooker should make a Guesstimate for all this.
I indeed upvoted it for the update / generally valuable contribution to the discussion.