The world is probably going to lose 5 2.5-10% of its population (380 190-760 million, see here for the reason for my edit), worse than the Spanish flu even on a percentage basis. I didn’t realize this until now (or rather, these facts didn’t become salient until now), but the current CFR estimates for COVID-19 are based on hospitals not being overwhelmed, whereas Spanish flu CFR was based on hospitals being overwhelmed (plus they didn’t have the life-saving technology we have today anyway, like oxygen concentrator and mechanical ventilator). If hospitals are overwhelmed, which seems very likely at this point, most of the people needing to be hospitalized (10-20% of infected, which will themselves be ~50% of world population according to epidemiologists) will probably die. See Forget about mortality rate, this is why you should be worried about coronavirus for more details but I actually arrived at this conclusion myself shortly before coming across that. My own realization was triggered by reading this post.
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.
I think the estimates in your links are not central estimates, even conditioning on 10% of the world being infected. The analysis in the Medium article basically assumes the worst case on every axis. So yeah, that will look pretty bad. And I think it is a good way to get a picture of what the right tail on this looks like. But it’s pretty far from the most likely outcome. Mitigating factors that are ignored:
Related to the above, we’re starting to get a sense of how it spreads, which should help us to slow the spread
Fatality rates so far may be much smaller than these worst case estimates, if the number of mild cases that were not detected is large. This is more likely to be true in Wuhan, where capacity for testing may have been stressed as well as capacity for treating. It is also more likely in the worlds where where ~50% of people become infected
Most published estimates of R0 are closer to the smaller end of the scale reported in that Medium article (2-2.5 from the WHO, 2-3 from JAMA, vs 1.4-3.8), and for comparison to influenza, 1.28 is on the smaller end of flu outbreak R0 estimates (~1.5 for the 2009 outbreak, and why did he use a point value with three significant figures for such an imprecisely measured thing?)
Any measure to slow down the virus will spread out the stress to hospitals. It’s not as if we’ll wake up one morning and half of all people in our town will be infected. We should be less concerned about how many people will be infected and more concerned about how many people will be infected at once.
Warmer weather usually makes these things less bad, which may slow the spread over the coming months
If it looks like I’m reaching for arguments for not being worried, that’s because I kind of am (though I do think everything I said here is true). But that’s how the Medium article reads to me. It is very unlikely that all of the bad things will happen and none of the good things will happen.
It seems like your arguments can be summed up as “if we slow the spread enough, hospitals won’t be overwhelmed” but the US only has 924,107 beds in total, and if each case takes 4 weeks to recover (“People with more severe cases generally recover in three to six weeks.”) we can treat 11 million people or 3.4% of the population over a year, but that would mean death rates from other diseases would rise a lot since those patients wouldn’t have beds. Many countries do have a lot more beds per capita than the US (which surprises and confuses me) but presumably they’re almost all being used already?
ETA: Actually the limiting factor probably isn’t hospital beds but equipment for treating respiratory disease. For example according to this paper:
The median number of full-feature mechanical ventilators per 100,000 population for individual states is 19.7 (interquartile ratio 17.2-23.1)
This works out to be about 65,000 in the whole country which is a small fraction of what’s needed to treat the number of people who will need them (.05 * .5 * 327e6 = 8,175,000) even spread out over a year or two.
I’m also arguing that we might just have many fewer severe cases than these right-tail estimates are indicating. So far, Hubei has only had .1% of their population get confirmed cases, for example, and I think that many scenarios in which >10% of people are infected globally are ones in which the actual number of cases in Hubei is much larger than .1%.
I also think there are more reasons for expecting fewer severe cases in many parts of the world than in China, like the increased prevalence of smoking in China, relative to places like the US.
in which the actual number of cases in Hubei is much larger than .1%.
I think Wei Dai’s position is compatible with there being 10x as many undiagnosed cases in Hubei as diagnosed ones. But maybe you’re suggesting that it could be more like 50x?
10x currently seems like the right ballpark to me.
Those predictions are based on 80% of cases being mild. My claim is that if 90% of cases are undiagnosed, then substantially less than 20% will be severe.
As things get out of hand, I would expect countries to throw a ton of money at it, basically like declaring war. When a ton of money is thrown at it, will hospitals still be overwhelmed?
For many places, like the US, needing approvals is more of a problem than cost, when it comes to building new hospitals or ventilators or so on. It seems quite possible that the regulations will shift as a result of the experience here.
Makes sense. So with that expectation of more money and less regulations, how does that affect our expectation that hospitals will be overwhelmed, and thus that death rates will be higher?
Do you think shorting the market is a good idea still?
If 2.5 to 10% of the world population will indeed die, I cannot possibly see how the stock market would be low right now. A global recession or depression would result and that would be much worse than where it’s at now.
What’s your model for why 2.5-10% of the world dying causes a global recession? It’s plausible to me from the mortality demographics that the risk of death is much higher among older people, and the impact on the workforce will be small, on the order of 0.4% of the workforce for 2.5% of the population. So while it’s a bit morbid to think about, it is not obvious mortality causes a sustained economic downturn.
Widespread panic and quarantine also seems dangerous to the economy. But there was pretty strong panic in Hong Kong during SARS, and the result was a V-shaped recovery: a transient shock, followed by increased economic growth the following year. The current coronavirus will surely last longer and have more psychological weight due to the sheer number of deaths and global nature, but I don’t have a concrete picture of how that leads to a recession.
Is the 5-10% global mortality prediction conditional on COVID-19 infecting >10% of the world, or unconditional?
It’s more or less unconditional at this point, since it’s not clear what could stop the virus from infecting >10% of the world. If you watch the press conferences for the Seattle-area outbreak, the officials in charge are saying it’s unlikely that they can contain it.
What do you think of the prospects for antivirals like remdesivir to be tested and mass-produced? How much could they lower CFR?
I think the prospects are good for successful test but I don’t know about scaling up production. I’ve asked this myself in various places and have not gotten any answers.
Why do you think other predictions, such as those given by Metaculus 1, 2, 3 are much less pessimistic?
I don’t have time to go through all those comments to find out where people gave their reasons. If you’ve read them, can you point to some that give the best arguments for their predictions? Then I can compare with my reasons...
Do you think shorting the market is a good idea still?
Yes, if my prediction is right and the market has only priced in a much lower death rate. I’m not as confident about this as I was in my original bet though. ETA: Mainly because of uncertainty about antivirals.
I think that your estimate of 2.5-10% population loss is derived from (50% infected) * (10-20% “severely ill” from the JAMA article) * (50-100% of severely ill patients die with severe overcrowding). I think that the last 2 numbers are questionable. Worldometers says that 8% of current cases are “serious/critical”, which as I understand it is roughly the threshold for being in the ICU/requiring breathing machine in normal circumstances. To get a 10-20% case fatality rate, we would need most patients with serious cases to die (feasible given lack of breathing machines), as well as a few percent of non-critical patients.
Estimates I made seem to line up with a fatality rate of less than 10%. I expect around 70% of critical patients to die without critical equipment (ventilators/vasopressors), so as of writing my estimate is in the ballpark of the following three numbers:
Diamond Princess: (7 actual dead + (36 critical * 70%))/706 = 4.5%
World actual CFR adjusted with formula from here (3,119 dead) / (3,119 + 48,163 recovered) = 6%
Higher fatality rate for overcrowding pushes this up, but on the other hand I think there is huge under-reporting of minor cases, since most countries are not testing everyone who was exposed.
WHO Report source: 5% “needed artificial respiration” * 70% + (10% “needed O2″ but not artificial respiration) * (wild guess 30% of these patients die) = 6.5%
Basically I’m confused at the gap between these reference numbers and the 10-20% fatality rate that seems to be required for the upper end of that 2.5-10% global population loss estimate. Do you just expect overcrowding to cause much bigger problems than shortages of breathing machines and other such equipment?
Notably eg the Diamond Princess number (36) isn’t critical cases, but “serious/critical” cases. Do you expect 70% fatality without critical equipment for the entire “serious/critical” category, or just the “critical” sub-category?
Further, curious about if there are explicable reasons underlying your 70% estimate, cause I am trying to estimate this myself too. Notably, I’ve seen numbers from China that 50% of critically ill patients die *with* medical care.
The “serious/critical” category on worldometer seems to mean “intensive care”, or “critical” as defined in the WHO report. Singapore’s 6% “serious/critical” means ICU admission. China’s 8.5% is close to the 6.1% on the WHO report—see below. Italy’s 10% is also intensive care, though their criteria for ICU admission could be different. It’s possible that the Diamond Princess number uses different criteria; do you know that they do? Anyway, the WHO said:
13.1% have severe disease [...] and 6.1% are critical. [...]
Severe cases are defined as tachypnoea (≧30 breaths/ min) or oxygen saturation ≤93% at
rest, or PaO2/FIO2 <300 mmHg. Critical cases are defined as respiratory failure requiring mechanical ventilation, shock or other organ failure that requires intensive care. About a quarter of severe and critical cases [i.e. about the number of critical cases] require mechanical ventilation while the remaining 75% require only oxygen supplementation.
Most ICU patients need mechanical ventilation, close monitoring for administration of drugs like IV vasopressors (1:1 or 2:1 nurse:patient ratio), or other scarce resources. But the inference from that to 70% mortality in an organized, severely-overcrowded hospital is mostly medical intuition. I have significant uncertainty from lack of reference classes, and also don’t know how well hospitals will be organized.
Yes, the current fatality rate is low due to the factor you mention. But it’s also high due to the fact that many cases are mild and not being counted, right? Isn’t it unclear at this point which effect is stronger?
The vast majority of those infected sooner or later develop symptoms. Cases of people in whom the virus has been detected and who do not have symptoms at that time are rare—and most of them fall ill in the next few days.
10% to 20% of hospitalized patients becoming severely ill
Connect these dots, along with the fact that Singapore has been doing extremely aggressive contact tracing and has been successful enough to almost stop the spread, I think Singapore can’t have many uncounted mild or asymptomatic cases, and their severely ill rate is still 10% to 20%. I assumed 20% earlier, so maybe the lower end of my estimate should be discounted by another half to arrive at 2.5%-10% overall death rate.
From a quick and dirty skim of the linked article, it looks like the 10-20% number may not be based directly on the Singapore data—but possibly it is based on China data. Quote in context:
Fifth, the medical community needs to collectively find better ways to communicate and engage the public in the social media era. The public is understandably anxious about COVID-19, given how rapidly the epidemic has spread with 10% to 20% of hospitalized patients becoming severely ill.
According to the data here (https://www.worldometers.info/coronavirus/) only 6⁄108 = 5.6% are in serious or critical condition. That’s about the same as on Diamond Princess (36/699=5.1%).
So 5.2% of cases in serious/critical condition, plus 0.9% deaths in the sum of these two especially relevant populations.
Hmm, I had noticed that dividing the number of serious or critical cases by the number of total cases gives less than 10%, but assumed that’s because not all cases had enough time to progress to where they might become serious or critical yet, and the 10-20% was the authors adjusting for that. But I guess you’re right that maybe they just based it on China’s data.
So extrapolating from the current Singapore+Diamond Princess numbers, assuming 50% worldwide infection rate and 0-100% dead among severe/critical cases—and no hospital care—about 0.5%-3% of the world population will die.
So the graph above implies that every demographic has approximately equal hospitalization rates, which other sources suggest are 15% to 20%.
This is a weird pattern – why are so many young people getting hospitalized if almost none of them die? Either the medical system is serving these people really well (ie they would die if they didn’t go the hospital, but everyone does make it to the hospital, and the hospital saves everyone who goes there), they are being hospitalized unnecessarily (ie they would live even if they didn’t go the hospital, but they do anyway), or it’s statistical shenanigans (eg most statistics are collected at the hospital, so it looks like everybody goes to the hospital).
Are these an overestimate? Maybe most cases never come to the government’s attention? There’s some evidence for this.
The young people who get hospitalized and recover are mostly not needing ICU or mechanical ventilation (~2% of total young adult cases do, i.e. 10% of the hospitalized young adults I guess), but I can’t find data on what interventions they are getting and whether they’re lifesaving.
This pattern doesn’t repeat itself in other countries. That makes me wonder whether Singapore might have a blanket policy to hospitalize all patients to monitor them (and kind of also make sure they don’t go anywhere and infect more people)? While that wouldn’t be my first reading when I read the above sentence, I find such alternative hypotheses more likely than “there are very few truly mild cases” because there seems to be a lot of counterevidence to that from other countries’ reports.
Edit: Comment was based on a misreading of Wei’s claim & can be ignored for that matter.
Connect these dots, along with the fact that Singapore has been doing extremely aggressive contact tracing and has been successful enough to almost stop the spread, I think Singapore can’t have many uncounted mild or asymptomatic cases, and their severely ill rate is still 10% to 20%.
Do you have a citation for the claim that Singapore can’t have many mild or asymptomatic cases? The article you cite says:
Close contacts are identified and those individuals without symptoms are quarantined for 14 days from last exposure. As of February 19, a total of 2593 close contacts have been identified. Of these, 1172 are currently quarantined and 1421 have completed their quarantine.5Contacts with symptoms are tested for COVID-19 using RT-PCR.
The bold bit suggests that asymptomatic [or, I suspect, minimally symptomatic] people aren’t being tested
Some more suggestive evidence that Singapore might not be testing asymptomatic/minimally symptomatic people:
The COVID-19 swab test kit deployed at [travel] checkpoints allows us to test beyond persons who are referred to hospitals, and extend testing to lower-risk symptomatic travellers as an added precautionary measure. This additional testing capability deployed upfront at checkpoints further increases our likelihood of detecting imported cases at the point of entry. As with any test, a negative result does not completely rule out the possibility of infection. As such, symptomatic travellers with a negative test result should continue to minimise social contact and seek medical attention should symptoms not improve over the next three days.
If they were already testing lots of asymptomatic cases, it would be odd to say testing *symptomatic travelers* is allowing them to test beyond people referred to hospitals.”
I wonder if people are assuming that intense contact tracing means that contacts will be tested by default even if asymptomatic. I’m not an expert but my understanding is that this isn’t necessarily the default (and particularly not in a situation where they presumably don’t have an infinite supply of kits or healthcare workers to do the diagnostics). Depends on how close the contact was, the specific disease, etc, but I think default is to call the contact every day to check if they’ve developed symptoms. Would be great if an actual doctor/epidemiologist chimed in.
Singapore’s description of their contact tracing is vague but consistent with my understanding:
Once identified, MOH will closely monitor all close contacts. As a precautionary measure, they will be quarantined for 14 days from their last exposure to the patient. In addition, all other identified contacts who have a low risk of being infected will be under active surveillance, and will be contacted daily to monitor their health status.
14. As of 3 March 2020, 12pm, MOH has identified 3,173 close contacts who have been quarantined. Of these, 336 are currently quarantined, and 2,837 have completed their quarantine.
Yes as part of a team on standby briefed on contact tracing protocol in Singapore I can confirm, we only call and inform potential contacts . They are not tested unless I’ll.
I think you’re right, I was just mistaken in assuming that Singapore tested everyone rather than only people with symptoms. However WHO has reported that 75% of asymptomatic cases detected in China develop symptoms later, so asymptomatic cases seemingly won’t reduce the global fatality rate much.
Seems possible but I don’t really understand where China’s claims about asymptomatic cases are coming from so I’ve been hesitant about putting too much weight on them. Copying some thoughts on this over from a FB comment I wrote (apologies that some of it doesn’t make total sense w/o context).
tl;dr I’m pretty unsure whether China actually has so few minimally symptomatic/asymptomatic cases.
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Those 320,000 people were at fever clinics, so I think none of them should be asymptomatic.
The report does say “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.”
But from a quick skim, I don’t think the basis for that finding is mentioned anywhere in the report. My guess is that Chinese officials told them that there were very few asymptomatic cases among people who were tested through contact tracing (which theoretically should test cases whether or not they’re symptomatic.
I haven’t really read anything from experts on this but my speculative guess is that we shouldn’t rely too heavily on claims about data from China’s contact tracing. The report claims that 100% of contacts were successfully traced in Shenzen and Guangdong and 99% in Sichuan. “100%” is a bit of a red flag coming from that regime.
I just want to flag that I find this point much more concerning than the point about hospital crowding (which I think is already factored in to some degree by current CFR estimates). I didn’t know about virtually all Singapore cases requiring hospitalization. But I notice I’m confused. If that’s true, then where does the impression come from that there are so many mild cases? You seem to say it’s mostly timing and that mild cases eventually become severe. But it would seem that if this tended to happen, surely we’d have heard about it earlier than now? (And also it would mean that China must have about 10x more deaths than they are reporting.)
Edit: Okay I see this wasn’t your point. In that case, ignore my comment.
I didn’t know about virtually all Singapore cases requiring hospitalization.
That wasn’t my point. I think they were hospitalized for isolation and observation/treatment, not because they required it. My understanding is that “severely ill” are the ones truly requiring hospitalization, i.e., would probably die without it.
Looks like the Diamond Princess cruise ship will be a godsend. Data from people who have been blanket tested over and over and so you actually know you have a good population that you can follow the disease course and know you are not missing anyone.
Just saw this just now. Basically, it’s evidence that the virus has been spreading below the radar in Washington State for the past 6 weeks. People on the sub are taking this to mean the fatality rate is lower than commonly thought, since we should be seeing more hospitalizations if it truly is 20% serious. That said, I’m not sure I agree with that take -- 6 weeks of spread from 1 initial person is only ~100 people I think, and maybe 20 serious cases of influenza could go under the radar.
Also, due to exponential spread, most of the 100 (or low hundreds) will have been infected recently, not enough time to have progressed to “severely ill” yet.
9 people have died in the Seattle area now, which is higher than even what I was expecting, given that hospitals aren’t overwhelmed yet, and not that many people should have gotten infected early enough to have progressed so far in their disease. (Average time from symptoms to death is 14 days.) Might be just an outlier with a nursing home having gotten infected early, but there are 2 deaths even outside that.
but the current CFR estimates for COVID-19 are based on hospitals not being overwhelmed
That seems a bit misleading because current CFR estimates are largely driven by cases from Hubei province, where the hospitals are already overwhelmed. You could argue that there’s room for things to get worse, and I probably agree with that. But I don’t see how this consideration warrants such a huge update to the CFR estimates. It seems to be already factored in to quite a large degree.
For specifics: The Imperial College estimate gave a 95% confidence interval for the “total case fatality rate” around February 10th. The interval ranged from 0.5% to 4%, with 1% being the median/EV (so much higher likelihood for lower values in that range). The way I interpreted this, their total CFR referred to their best guess about the prognosis of all people infected on February 10th. That included a large majority of patients in Hubei province. For patients who were diagnosed there, the estimated CFR was 18% (11-85% for the 95% confidence interval). Those scarily high 18% are already part of the Imperial College’s 1% expected death rate estimate. It’s still only 1% instead of anything more close to 18% both because disease runouts in other countries (with less overcrowded hospitals) were less severe, and because they estimated that even in Hubei province, there must be a large number of cases with only mild symptoms. The second factor must be responsible for the bigger update (because there simply hadn’t been many cases overseas or in other Chinese cities at that time).
Elsewhere in this comment thread, you write that mild or initially asymptomatic cases may later develop to become more severe. I haven’t heard that point before. If that was true, that would be a stronger reason for me to conclude that CFR estimates by the Imperial College will be way too low. (And just to be clear, I think it’s defensible to argue that hospital crowding and other conditions related to a worst-case pandemic can become a lot worse than even the situation in Hubei province, so I’m not saying I’m confident that current CFR estimates will remain accurate during worst-case pandemic conditions. I’m just pointing out that the consideration is already factored in to some degree, so arguing about how large the update should be exactly seems to require more detailed arguments.)
That seems a bit misleading because current CFR estimates are largely driven by cases from Hubei province, where the hospitals are already overwhelmed. You could argue that there’s room for things to get worse, and I probably agree with that. But I don’t see how this consideration warrants such a huge update to the CFR estimates. It seems to be already factored in to quite a large degree.
My understanding is that China sent a large number of doctors from other provinces to Hubei (can’t find the source now), and the outbreak was controlled via draconian means unlikely to be reproducible in most parts of the world. Hubei has a population of 58 million and only 66907 confirmed cases, so the hospitals were not nearly as overwhelmed as they could have been.
ETA: Looking at the Imperial paper you cited, the (uncorrected) estimated CFR being 18% was not the result of hospitals overwhelmed, but undercounting infections within Hubei (see page 10), which they then corrected to 1%. So I think this is consistent with the CFR estimate being based on hospitals not being overwhelmed, and it being much higher in the future when hospitals throughout the world will be overwhelmed.
Good point about importing doctors from other cities. This won’t be possible anymore if a country has the virus everywhere.
Room upward for more hospital crowding: Okay yeah, crowding could be a lot worse still. But self-isolation of the entire population seems like an option that can be implemented by any country to slow the peak of an outbreak. It doesn’t seem to require China-level control over a population. So maybe it’s unlikely that things would become worse than they did in Hubei? I guess you could argue that unless the government is extremely strict about people not being allowed to go outside, then too many people will still do it and get infected.
I think you’re giving convincing arguments to be a lot more pessimistic than the 1% expected CFR. The main counterconsiderations I see are that with more preparedness, countries can better slow down the peak of an epidemic. I don’t think cities are likely to quickly end up in a state that’s as bad as in Wuhan because by the time the hospitals start to crowd, the cities will already have been giving strongly worded advice about self-isolating at home for many weeks. This time window was missed in Wuhan. (But I was already aware of those considerations, so for me your points still provided a large update. I don’t expect to end up anywhere close to the high numbers you’re giving, but I’ll have to think about it more and I definitely think 2% total CFR seems possible or even likely now as we forecast scenarios approaching one billion cases.)
But self-isolation of the entire population seems like an option that can be implemented by any country to slow the peak of an outbreak.
0.1% of Hubei’s population have a confirmed infection, and its hospitals are already at the breaking point (even with national resources transferred into it). If this is the limit, then hospitals can treat at most 0.1% of the population per month, so it would take 50-100 months to treat the 5-10% who will require hospitalization, which is not a realistic amount of time for self-isolation. Even 10 months is not realistic (without totally ruining the economy) so it seems “slowing the peak” just won’t help much.
The WHO report said some 90% of people had fever. Maybe the tests have a significant false neg rate, or theyre not testing enough people, but I am worried that few mild cases are being missed.
I’m very interested in seeing how the Diamond Princess plays out. On feb 20, some half of the cases were asymptomatic. Wikipedia hasn’t been updated with any data since then. This bit feels cruxy to me.
FWIW, https://www.worldometers.info/coronavirus/ counts all confirmed cases and has a table by country, which lists the Diamond Princess separately (“international conveyance”). It doesn’t distinguish asymptomatic from mild, but does separate out “serious, critical” cases, which stand at 36/705 (plus 7/705 deaths and 100/705 recovered).
I’m confused by the predictions of death rates for the global population—seems like that’s what would happen only if the 50% of world population is infected all at once. Is it just exponential growth that’s doing the work there? I’m also confused about how long contagion is well-modelled as exponential
The world is probably going to lose
52.5-10% of its population (380190-760 million, see here for the reason for my edit), worse than the Spanish flu even on a percentage basis. I didn’t realize this until now (or rather, these facts didn’t become salient until now), but the current CFR estimates for COVID-19 are based on hospitals not being overwhelmed, whereas Spanish flu CFR was based on hospitals being overwhelmed (plus they didn’t have the life-saving technology we have today anyway, like oxygen concentrator and mechanical ventilator). If hospitals are overwhelmed, which seems very likely at this point, most of the people needing to be hospitalized (10-20% of infected, which will themselves be ~50% of world population according to epidemiologists) will probably die. See Forget about mortality rate, this is why you should be worried about coronavirus for more details but I actually arrived at this conclusion myself shortly before coming across that. My own realization was triggered by reading this post.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.
I think the estimates in your links are not central estimates, even conditioning on 10% of the world being infected. The analysis in the Medium article basically assumes the worst case on every axis. So yeah, that will look pretty bad. And I think it is a good way to get a picture of what the right tail on this looks like. But it’s pretty far from the most likely outcome. Mitigating factors that are ignored:
China got a lot better at managing the epidemic over time, and everyone can learn from that. (See the WHO report linked in the reddit post: https://www.who.int/docs/default-source/coronaviruse/who-china-joint-mission-on-covid-19-final-report.pdf)
Related to the above, we’re starting to get a sense of how it spreads, which should help us to slow the spread
Fatality rates so far may be much smaller than these worst case estimates, if the number of mild cases that were not detected is large. This is more likely to be true in Wuhan, where capacity for testing may have been stressed as well as capacity for treating. It is also more likely in the worlds where where ~50% of people become infected
Most published estimates of R0 are closer to the smaller end of the scale reported in that Medium article (2-2.5 from the WHO, 2-3 from JAMA, vs 1.4-3.8), and for comparison to influenza, 1.28 is on the smaller end of flu outbreak R0 estimates (~1.5 for the 2009 outbreak, and why did he use a point value with three significant figures for such an imprecisely measured thing?)
Any measure to slow down the virus will spread out the stress to hospitals. It’s not as if we’ll wake up one morning and half of all people in our town will be infected. We should be less concerned about how many people will be infected and more concerned about how many people will be infected at once.
Warmer weather usually makes these things less bad, which may slow the spread over the coming months
There is some evidence that east Asian populations are more susceptible (https://jamanetwork.com/journals/jama/fullarticle/2762510)
If it looks like I’m reaching for arguments for not being worried, that’s because I kind of am (though I do think everything I said here is true). But that’s how the Medium article reads to me. It is very unlikely that all of the bad things will happen and none of the good things will happen.
It seems like your arguments can be summed up as “if we slow the spread enough, hospitals won’t be overwhelmed” but the US only has 924,107 beds in total, and if each case takes 4 weeks to recover (“People with more severe cases generally recover in three to six weeks.”) we can treat 11 million people or 3.4% of the population over a year, but that would mean death rates from other diseases would rise a lot since those patients wouldn’t have beds. Many countries do have a lot more beds per capita than the US (which surprises and confuses me) but presumably they’re almost all being used already?
ETA: Actually the limiting factor probably isn’t hospital beds but equipment for treating respiratory disease. For example according to this paper:
This works out to be about 65,000 in the whole country which is a small fraction of what’s needed to treat the number of people who will need them (.05 * .5 * 327e6 = 8,175,000) even spread out over a year or two.
I’m also arguing that we might just have many fewer severe cases than these right-tail estimates are indicating. So far, Hubei has only had .1% of their population get confirmed cases, for example, and I think that many scenarios in which >10% of people are infected globally are ones in which the actual number of cases in Hubei is much larger than .1%.
I also think there are more reasons for expecting fewer severe cases in many parts of the world than in China, like the increased prevalence of smoking in China, relative to places like the US.
I think Wei Dai’s position is compatible with there being 10x as many undiagnosed cases in Hubei as diagnosed ones. But maybe you’re suggesting that it could be more like 50x?
10x currently seems like the right ballpark to me.
Those predictions are based on 80% of cases being mild. My claim is that if 90% of cases are undiagnosed, then substantially less than 20% will be severe.
Then you wouldn’t expect close contacts to both have severe disease frequently. I think this has occurred too frequently.
Data to support this: Daegu has a population of 2.4 million, 3146 COVID-19 patients, and 2000 patients waiting for hospital beds, meaning it can treat .05% of the population at a time. Note that South Korea has the second highest number of hospital beds per capita in the world.
As things get out of hand, I would expect countries to throw a ton of money at it, basically like declaring war. When a ton of money is thrown at it, will hospitals still be overwhelmed?
For many places, like the US, needing approvals is more of a problem than cost, when it comes to building new hospitals or ventilators or so on. It seems quite possible that the regulations will shift as a result of the experience here.
Makes sense. So with that expectation of more money and less regulations, how does that affect our expectation that hospitals will be overwhelmed, and thus that death rates will be higher?
Is the 5-10% global mortality prediction conditional on COVID-19 infecting >10% of the world, or unconditional?
What do you think of the prospects for antivirals like remdesivir to be tested and mass-produced? How much could they lower CFR?
Why do you think other predictions, such as those given by Metaculus 1, 2, 3 are much less pessimistic?
Do you think shorting the market is a good idea still?
If 2.5 to 10% of the world population will indeed die, I cannot possibly see how the stock market would be low right now. A global recession or depression would result and that would be much worse than where it’s at now.
What’s your model for why 2.5-10% of the world dying causes a global recession? It’s plausible to me from the mortality demographics that the risk of death is much higher among older people, and the impact on the workforce will be small, on the order of 0.4% of the workforce for 2.5% of the population. So while it’s a bit morbid to think about, it is not obvious mortality causes a sustained economic downturn.
Widespread panic and quarantine also seems dangerous to the economy. But there was pretty strong panic in Hong Kong during SARS, and the result was a V-shaped recovery: a transient shock, followed by increased economic growth the following year. The current coronavirus will surely last longer and have more psychological weight due to the sheer number of deaths and global nature, but I don’t have a concrete picture of how that leads to a recession.
It’s more or less unconditional at this point, since it’s not clear what could stop the virus from infecting >10% of the world. If you watch the press conferences for the Seattle-area outbreak, the officials in charge are saying it’s unlikely that they can contain it.
I think the prospects are good for successful test but I don’t know about scaling up production. I’ve asked this myself in various places and have not gotten any answers.
I don’t have time to go through all those comments to find out where people gave their reasons. If you’ve read them, can you point to some that give the best arguments for their predictions? Then I can compare with my reasons...
Yes, if my prediction is right and the market has only priced in a much lower death rate. I’m not as confident about this as I was in my original bet though. ETA: Mainly because of uncertainty about antivirals.
I think that your estimate of 2.5-10% population loss is derived from (50% infected) * (10-20% “severely ill” from the JAMA article) * (50-100% of severely ill patients die with severe overcrowding). I think that the last 2 numbers are questionable. Worldometers says that 8% of current cases are “serious/critical”, which as I understand it is roughly the threshold for being in the ICU/requiring breathing machine in normal circumstances. To get a 10-20% case fatality rate, we would need most patients with serious cases to die (feasible given lack of breathing machines), as well as a few percent of non-critical patients.
Estimates I made seem to line up with a fatality rate of less than 10%. I expect around 70% of critical patients to die without critical equipment (ventilators/vasopressors), so as of writing my estimate is in the ballpark of the following three numbers:
Diamond Princess: (7 actual dead + (36 critical * 70%))/706 = 4.5%
World actual CFR adjusted with formula from here (3,119 dead) / (3,119 + 48,163 recovered) = 6%
Higher fatality rate for overcrowding pushes this up, but on the other hand I think there is huge under-reporting of minor cases, since most countries are not testing everyone who was exposed.
WHO Report source: 5% “needed artificial respiration” * 70% + (10% “needed O2″ but not artificial respiration) * (wild guess 30% of these patients die) = 6.5%
Basically I’m confused at the gap between these reference numbers and the 10-20% fatality rate that seems to be required for the upper end of that 2.5-10% global population loss estimate. Do you just expect overcrowding to cause much bigger problems than shortages of breathing machines and other such equipment?
Notably eg the Diamond Princess number (36) isn’t critical cases, but “serious/critical” cases. Do you expect 70% fatality without critical equipment for the entire “serious/critical” category, or just the “critical” sub-category?
Further, curious about if there are explicable reasons underlying your 70% estimate, cause I am trying to estimate this myself too. Notably, I’ve seen numbers from China that 50% of critically ill patients die *with* medical care.
The “serious/critical” category on worldometer seems to mean “intensive care”, or “critical” as defined in the WHO report. Singapore’s 6% “serious/critical” means ICU admission. China’s 8.5% is close to the 6.1% on the WHO report—see below. Italy’s 10% is also intensive care, though their criteria for ICU admission could be different. It’s possible that the Diamond Princess number uses different criteria; do you know that they do? Anyway, the WHO said:
Most ICU patients need mechanical ventilation, close monitoring for administration of drugs like IV vasopressors (1:1 or 2:1 nurse:patient ratio), or other scarce resources. But the inference from that to 70% mortality in an organized, severely-overcrowded hospital is mostly medical intuition. I have significant uncertainty from lack of reference classes, and also don’t know how well hospitals will be organized.
Yes, the current fatality rate is low due to the factor you mention. But it’s also high due to the fact that many cases are mild and not being counted, right? Isn’t it unclear at this point which effect is stronger?
From here:
From here, describing Singapore:
Connect these dots, along with the fact that Singapore has been doing extremely aggressive contact tracing and has been successful enough to almost stop the spread, I think Singapore can’t have many uncounted mild or asymptomatic cases, and their severely ill rate is still 10% to 20%. I assumed 20% earlier, so maybe the lower end of my estimate should be discounted by another half to arrive at 2.5%-10% overall death rate.
From a quick and dirty skim of the linked article, it looks like the 10-20% number may not be based directly on the Singapore data—but possibly it is based on China data. Quote in context:
According to the data here (https://www.worldometers.info/coronavirus/) only 6⁄108 = 5.6% are in serious or critical condition. That’s about the same as on Diamond Princess (36/699=5.1%).
So 5.2% of cases in serious/critical condition, plus 0.9% deaths in the sum of these two especially relevant populations.
Hmm, I had noticed that dividing the number of serious or critical cases by the number of total cases gives less than 10%, but assumed that’s because not all cases had enough time to progress to where they might become serious or critical yet, and the 10-20% was the authors adjusting for that. But I guess you’re right that maybe they just based it on China’s data.
So extrapolating from the current Singapore+Diamond Princess numbers, assuming 50% worldwide infection rate and 0-100% dead among severe/critical cases—and no hospital care—about 0.5%-3% of the world population will die.
In other words, a CFR of 1-6%, with the lowest value overlapping with estimates being put out by governments right now.
EDIT: I just read Scotty’s new post on the subject and he’s confused by that 10-20% figure as well
The young people who get hospitalized and recover are mostly not needing ICU or mechanical ventilation (~2% of total young adult cases do, i.e. 10% of the hospitalized young adults I guess), but I can’t find data on what interventions they are getting and whether they’re lifesaving.
With regard to the timing of things, the recent WHO-China report has some interesting charts.
This pattern doesn’t repeat itself in other countries. That makes me wonder whether Singapore might have a blanket policy to hospitalize all patients to monitor them (and kind of also make sure they don’t go anywhere and infect more people)? While that wouldn’t be my first reading when I read the above sentence, I find such alternative hypotheses more likely than “there are very few truly mild cases” because there seems to be a lot of counterevidence to that from other countries’ reports.
Edit: Comment was based on a misreading of Wei’s claim & can be ignored for that matter.
Do you have a citation for the claim that Singapore can’t have many mild or asymptomatic cases? The article you cite says:
The bold bit suggests that asymptomatic [or, I suspect, minimally symptomatic] people aren’t being tested
Some more suggestive evidence that Singapore might not be testing asymptomatic/minimally symptomatic people:
https://www.moh.gov.sg/news-highlights/details/additional-precautionary-measures-in-response-to-escalating-global-situation
If they were already testing lots of asymptomatic cases, it would be odd to say testing *symptomatic travelers* is allowing them to test beyond people referred to hospitals.”
I wonder if people are assuming that intense contact tracing means that contacts will be tested by default even if asymptomatic. I’m not an expert but my understanding is that this isn’t necessarily the default (and particularly not in a situation where they presumably don’t have an infinite supply of kits or healthcare workers to do the diagnostics). Depends on how close the contact was, the specific disease, etc, but I think default is to call the contact every day to check if they’ve developed symptoms. Would be great if an actual doctor/epidemiologist chimed in.
Singapore’s description of their contact tracing is vague but consistent with my understanding:
https://www.moh.gov.sg/news-highlights/details/two-new-cases-of-covid-19-infection-confirmed
If they were administering tests to asymptomatic contacts, I think it’s likely they’d have said so here.
Yes as part of a team on standby briefed on contact tracing protocol in Singapore I can confirm, we only call and inform potential contacts . They are not tested unless I’ll.
Thanks for confirming!
How ill do they have to be? If a contact is feeling under the weather in a nonspecific way and has a cough, is that enough for them to get tested?
Do you feel like you have any insight into whether underreporting of mild/minimally symptomatic/asymptomatic cases?
I think you’re right, I was just mistaken in assuming that Singapore tested everyone rather than only people with symptoms. However WHO has reported that 75% of asymptomatic cases detected in China develop symptoms later, so asymptomatic cases seemingly won’t reduce the global fatality rate much.
Seems possible but I don’t really understand where China’s claims about asymptomatic cases are coming from so I’ve been hesitant about putting too much weight on them. Copying some thoughts on this over from a FB comment I wrote (apologies that some of it doesn’t make total sense w/o context).
https://www.facebook.com/permalink.php?story_fbid=1073098183053785&id=100010608396052&comment_id=1073152789714991&reply_comment_id=1073889599641310
I just want to flag that I find this point much more concerning than the point about hospital crowding (which I think is already factored in to some degree by current CFR estimates). I didn’t know about virtually all Singapore cases requiring hospitalization. But I notice I’m confused. If that’s true, then where does the impression come from that there are so many mild cases? You seem to say it’s mostly timing and that mild cases eventually become severe. But it would seem that if this tended to happen, surely we’d have heard about it earlier than now? (And also it would mean that China must have about 10x more deaths than they are reporting.)
Edit: Okay I see this wasn’t your point. In that case, ignore my comment.
That wasn’t my point. I think they were hospitalized for isolation and observation/treatment, not because they required it. My understanding is that “severely ill” are the ones truly requiring hospitalization, i.e., would probably die without it.
Looks like the Diamond Princess cruise ship will be a godsend. Data from people who have been blanket tested over and over and so you actually know you have a good population that you can follow the disease course and know you are not missing anyone.
Just saw this just now. Basically, it’s evidence that the virus has been spreading below the radar in Washington State for the past 6 weeks. People on the sub are taking this to mean the fatality rate is lower than commonly thought, since we should be seeing more hospitalizations if it truly is 20% serious. That said, I’m not sure I agree with that take -- 6 weeks of spread from 1 initial person is only ~100 people I think, and maybe 20 serious cases of influenza could go under the radar.
Also, due to exponential spread, most of the 100 (or low hundreds) will have been infected recently, not enough time to have progressed to “severely ill” yet.
9 people have died in the Seattle area now, which is higher than even what I was expecting, given that hospitals aren’t overwhelmed yet, and not that many people should have gotten infected early enough to have progressed so far in their disease. (Average time from symptoms to death is 14 days.) Might be just an outlier with a nursing home having gotten infected early, but there are 2 deaths even outside that.
I’d greatly appreciate it if you could respond here:
https://www.greaterwrong.com/posts/ACyGvQchWzGjGkKgS/coronavirus-open-thread/comment/LeYZeyPGndDGaMhMQ
That seems a bit misleading because current CFR estimates are largely driven by cases from Hubei province, where the hospitals are already overwhelmed. You could argue that there’s room for things to get worse, and I probably agree with that. But I don’t see how this consideration warrants such a huge update to the CFR estimates. It seems to be already factored in to quite a large degree.
For specifics: The Imperial College estimate gave a 95% confidence interval for the “total case fatality rate” around February 10th. The interval ranged from 0.5% to 4%, with 1% being the median/EV (so much higher likelihood for lower values in that range). The way I interpreted this, their total CFR referred to their best guess about the prognosis of all people infected on February 10th. That included a large majority of patients in Hubei province. For patients who were diagnosed there, the estimated CFR was 18% (11-85% for the 95% confidence interval). Those scarily high 18% are already part of the Imperial College’s 1% expected death rate estimate. It’s still only 1% instead of anything more close to 18% both because disease runouts in other countries (with less overcrowded hospitals) were less severe, and because they estimated that even in Hubei province, there must be a large number of cases with only mild symptoms. The second factor must be responsible for the bigger update (because there simply hadn’t been many cases overseas or in other Chinese cities at that time).
Elsewhere in this comment thread, you write that mild or initially asymptomatic cases may later develop to become more severe. I haven’t heard that point before. If that was true, that would be a stronger reason for me to conclude that CFR estimates by the Imperial College will be way too low. (And just to be clear, I think it’s defensible to argue that hospital crowding and other conditions related to a worst-case pandemic can become a lot worse than even the situation in Hubei province, so I’m not saying I’m confident that current CFR estimates will remain accurate during worst-case pandemic conditions. I’m just pointing out that the consideration is already factored in to some degree, so arguing about how large the update should be exactly seems to require more detailed arguments.)
My understanding is that China sent a large number of doctors from other provinces to Hubei (can’t find the source now), and the outbreak was controlled via draconian means unlikely to be reproducible in most parts of the world. Hubei has a population of 58 million and only 66907 confirmed cases, so the hospitals were not nearly as overwhelmed as they could have been.
ETA: Looking at the Imperial paper you cited, the (uncorrected) estimated CFR being 18% was not the result of hospitals overwhelmed, but undercounting infections within Hubei (see page 10), which they then corrected to 1%. So I think this is consistent with the CFR estimate being based on hospitals not being overwhelmed, and it being much higher in the future when hospitals throughout the world will be overwhelmed.
Good point about importing doctors from other cities. This won’t be possible anymore if a country has the virus everywhere.
Room upward for more hospital crowding: Okay yeah, crowding could be a lot worse still. But self-isolation of the entire population seems like an option that can be implemented by any country to slow the peak of an outbreak. It doesn’t seem to require China-level control over a population. So maybe it’s unlikely that things would become worse than they did in Hubei? I guess you could argue that unless the government is extremely strict about people not being allowed to go outside, then too many people will still do it and get infected.
I think you’re giving convincing arguments to be a lot more pessimistic than the 1% expected CFR. The main counterconsiderations I see are that with more preparedness, countries can better slow down the peak of an epidemic. I don’t think cities are likely to quickly end up in a state that’s as bad as in Wuhan because by the time the hospitals start to crowd, the cities will already have been giving strongly worded advice about self-isolating at home for many weeks. This time window was missed in Wuhan. (But I was already aware of those considerations, so for me your points still provided a large update. I don’t expect to end up anywhere close to the high numbers you’re giving, but I’ll have to think about it more and I definitely think 2% total CFR seems possible or even likely now as we forecast scenarios approaching one billion cases.)
0.1% of Hubei’s population have a confirmed infection, and its hospitals are already at the breaking point (even with national resources transferred into it). If this is the limit, then hospitals can treat at most 0.1% of the population per month, so it would take 50-100 months to treat the 5-10% who will require hospitalization, which is not a realistic amount of time for self-isolation. Even 10 months is not realistic (without totally ruining the economy) so it seems “slowing the peak” just won’t help much.
The WHO report said some 90% of people had fever. Maybe the tests have a significant false neg rate, or theyre not testing enough people, but I am worried that few mild cases are being missed.
I’m very interested in seeing how the Diamond Princess plays out. On feb 20, some half of the cases were asymptomatic. Wikipedia hasn’t been updated with any data since then. This bit feels cruxy to me.
FWIW, https://www.worldometers.info/coronavirus/ counts all confirmed cases and has a table by country, which lists the Diamond Princess separately (“international conveyance”). It doesn’t distinguish asymptomatic from mild, but does separate out “serious, critical” cases, which stand at 36/705 (plus 7/705 deaths and 100/705 recovered).
I’m confused by the predictions of death rates for the global population—seems like that’s what would happen only if the 50% of world population is infected all at once. Is it just exponential growth that’s doing the work there? I’m also confused about how long contagion is well-modelled as exponential