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.
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.