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Adjusted Age-Specific Case Fatality Ratio During for COVID-19 in Hubei [pdf] (medrxiv.org)
129 points by tomerbd on March 8, 2020 | hide | past | favorite | 91 comments

This model is nice in principle, but its results depend crucially on what is ultimately an educated guess of the reporting rate of symptomatic cases.

This parameter can be found experimentally by testing for antibodies against the virus in a random sample of the population. This has not been done so far. As long as that's true, CFR estimates will be quite uncertain.

Also really interesting in this context is how Germany is looking more and more like a huge outlier in terms of fatality. Almost 1000 cases and 0 deaths so far. Sure, that may still change, but the outbreak has been going on for a while there already.

Or look at S Korea, 7313 cases 50 deaths, .68% CFR. Would like to see the age group breakdown.

If I had to guess why CFR is so much lower in S Korea, it's because they tend to test more widely, ie. don't only test when patients show up at the hospital with severe symptoms. Or in other words they are closer to the real CFR.

> Or look at S Korea, 7313 cases 50 deaths, .68% CFR. Would like to see the age group breakdown.

As of 2020-03-08 0:00 AM UTC+9 [1]:

              Patients        Deaths
    Age       (% of total)    (% in group)
    80+        212  (3.0%)      14  (6.6%)
    70--79     409  (5.7%)      18  (4.4%)
    60--69     878 (12.3%)      11  (1.3%)
    50--59    1349 (18.9%)       5  (0.4%)
    40--49     975 (13.7%)       1  (0.1%)
    30--39     760 (10.7%)       1  (0.1%)
    20--29    2133 (29.9%)       0  (0.0%)
    10--19     360  (5.0%)       0  (0.0%)
    0--9        58  (0.8%)       0  (0.0%)
    Total     7134              50  (0.7%)
[1] https://is.cdc.go.kr/upload_comm/syview/doc.html?fn=15836441... (p. 10)

Most of Korea's cases were discovered since late February and have not had a chance to either recover or die (i.e., the numerator is right-censored). Expect the CFR to rise there.

You are right. If you want some other statistics, as of 2020-03-07 there were 59 patients [1] that are under respiratory support or oxygen therapy and thus considered "severe".

[1] https://www.yna.co.kr/view/AKR20200307046000017

Or not. What about all the infected people who haven't had symptoms serious enough to warrant seeing a doctor and getting tested positive for Coronavirus?

That is a constant factor on the denominator, which is lower in Korea than elsewhere due to the availability of 10-minute drive-through tests. The factor on the numerator will be much higher at the start of an epidemic and go down to 1 when it completes.

The estimated average time to die for those who die from COVID-19 is 28 days. 28 days ago, Korea had fewer than 50 cases total.

How is the number of mild, untested cases a constant factor? If less serious patients start to get tested more frequently, this number will change.

> If less serious patients start to get tested more frequently, this number will change.

If everyone were tested, the denominator goes up by some constant factor. In Korea, people are already being tested at the first sign of cold symptoms.

The vaccines will change all these numbers.

Great data, thanks for taking the time to format it cleanly.

South Korea proactively tested people so their numbers are more skewed towards being the infection fatality rate (case fatality rate are those tested and cobfredtobe sick, ie sick enough to go to the doctor, get tested and be a confirmed case). Where as IFR is the estimate of everyone infected)

Also the demographics of those tested are skewed to the 20–40s age range as the member of a reclusive church was sick and didn’t say anything. They the proactively tested everyone they were in contact with at the church and the demographics of that church skew younger.

Does their test measure antibodies (meaning you were at some point exposed) or does it measure an active infection, or does it measure an active symptomatic infection?

I believe these are PCR tests, so they test for presence of the virus.

Afaik antibody tests do not yet exist but are in development

Yes South Korea are testing huge numbers. Worth watching closely.

Misleading. You can’t look at CFR with the denominator being total number of cases, at least in the exponential growth phase. It will massively understate the actual CFR.

But you can compare this ratio between countries that have similar numbers of cases to get a hint at relative detection efficacy, assuming constant CFR.

Germany's outbreak has not been going on for a while. They had 79 cases one week ago (https://web.archive.org/web/20200301001656/https://www.world...), and the number was 16 two weeks ago (https://web.archive.org/web/20200223003733/https://www.world...), and 14 four weeks ago (https://web.archive.org/web/20200210100748/https://www.world...). It takes weeks to die after getting infected.

That's not all there is to it, since the number of people infected grew at a similar pace in the early phase of an outbreak in different countries.

For example, the number of people infected in France and Germany is rising in near perfect synchrony, but France has 11 deaths now. Similarly, growth in the early phase of the South Korea outbreak looks nearly identical to Germany and France (with a ca. 2 week delay), and they had 10 deaths when they had 1000 infected.

Germany is looking increasingly anomalous every day.

There has to be a difference with respect to detection, unless it's something more out there like viral strain differences.

Actually, to the point of viral strain differences, I did come across this paper indicating exactly that idea— that there are two strains. I am not a scientist, so I cannot evaluate the veracity of the claims, but did find the work interesting and compelling: https://academic.oup.com/nsr/advance-article/doi/10.1093/nsr...

This was posted here a few days ago, and there were plenty of criticisms of it: https://news.ycombinator.com/item?id=22499152

79 cases last week to 1000 today doesn't indicate that there's been a new outbreak this week; it indicates that there's been an outbreak for a while and they're just now noticing. Those 79 people alone couldn't have infected 1000.

That, and with Christmas still in living memory the endangered age bracket is effectively quarantined anyways, not expecting the the next quarterly visit from children and grandchildren before the end of the month. Germany is a country of lonely old people.

I also saw this and found it odd. Assuming p=0.01, N=1000, k=0, the binomial probability is 0.00004317. At p=0.02, 0.03 it's even lower.

not following closely, but unfortunately i don't think the data is good enough to take a hard-stats point of view of significance - take for example the rest home cluster in washington state which would hugely skew the results on a 1k sample size.

South Korea are testing huge numbers of people, 10,000 per day, so the stats from there are instructive

But can you know that Germany is an outlier? Germany likely has a higher reporting rate than China so its numbers should be closer to the truth.

Germany is not testing nearly enough people. There are lots of reports of people with legitimate concerns that did not find a way to get tested. Northern italy is like 2 hours by car and each weekend thousands drive there for a short trip.

> Germany is not testing nearly enough people

Source? I’ve heard exactly the opposite - Germany is testing the whole cluster as soon as infection is found. That explains the low mortality.

In Germany they are tracking down clusters. As a random person you won't get tested, unless you visited a risky region, had contact with an infected person or your doctor orders a test for you. As a German, this strategy makes sense to me.

Considering the shortage of reagentia for these tests, that definitely makes sense.

Belgium only does tests on people who have recently been in regions at risk (China, Italy) or who have symptoms of pneumonia.

200 infected to date, zero deaths (so far).

Yep, that’s my understanding too and it makes perfect sense.

The low mortality is likely due to the recent introduction of the virus into the community there. It takes weeks to go from infection to ICU.

That’s incorrect, Germany is very much like France in terms of number of cases and their duration.

Something needs to explain the difference though between 939:0 in Germany and, e.g., 949:11 in France. Maybe the diagnoses in Germany are closer in time to infections? That would still point to a higher reporting rate in Germany vs. other countries.

France has had a continuous epidemic since early on, but Germany successfully contained the first outbreak (thanks to one phone call from China at the right time), then it was all quiet for a while and only now Germany is catching up in case count, at a very high speed. This means that Frances, with a comparable total, has far more cases that are old enough to have already played out negatively.

Germany and France have had very parallel number of cases: see https://github.com/CSSEGISandData/COVID-19/blob/master/csse_...

The first case in Germany was 3 days after the first in France. They reached 4 cases the same day. When France hit 11 cases, Germany already had 13 and for 15 days they both only got 1 to 3 more cases in total. They both began increasing a lot on the 26th of February.

You’re assuming that the reporting in Germany is the same as the reporting in France.

While they reached 4 cases the same day, that doesn’t mean that they had the same number of unknown infections. Let’s say France had 10x as many unknown infections than Germany. How would that impact the disparity in death count? And is this even a large enough sample size for that disparity to not just be explained to a high degree by mere chance?

I haven't followed the French situation closely, are the late February cases in France clearly unrelated to early February cases or could they be the result of a phase of undetected spread?

That's not true, case numbers in France and Germany are highly correlated. What you are saying would imply a substantial difference in growth rate between the two countries, which is easily disproved by looking at the data.

Exactly my point ;)

How much do we think healthcare and hospital stability was implicitly factored into this study given that the data was focused in Hubei? Meaning, if hospitals had to turn away patients, one would think the death rate would increase. If hospitals could receive all patients, one would presume the death rate would be lower? It's clear health care systems get overloaded even with a low symptomatic case saturation per capita.[0]

Related to this, what I haven't seen mentioned or discussed extensively is not only would the fatality rate increase for Covid-19 cases if hospitals are overloaded, but I would assume the fatality rate for _all other needs_ of a hospital would also increase. Does anyone know this has been assessed? (e.g., did Hubei see a notable increase in non-Covid-19 related deaths during this period?)

[0] https://www.aljazeera.com/news/2020/03/coronavirus-wreaks-ha...

I think we're seeing a small case study of this in the nursing home in Washington. Out of 120 residents, 13 are dead and have been identified with COVID-19. There were 11 more who died at the nursing home since Feb 19 and haven't been tested, but they said on average 3-6 residents die per month. I think the nursing home scenario is probably a worst case given both age and underlying health concerns (unlike elderly still living in their own home or with their families). Given the Seattle area medical infrastructure, this fatality rate can't be explained by overloading of our facilities.

I really disliked Fauci's comments that "the risk is low" to the American population, pointing to the rate of infection. He hedges this with some hand waving that it could change at any moment. I thought it was irresponsible to say the risk is low when they hadn't done any real testing and we've actually got outbreaks like in Kirkland. Regarding his comment that the WHO fatality rate is too high because of asymptomatic population and the denominator in reality is much higher. Fine. But he doesn't acknowledge that the numerator might be much higher as well. How many 80+ year olds, especially those with preexisting conditions, die and are assumed to have just passed from old age and the preexisting conditions. It is a characteristic of this virus that the people getting killed are the most likely ones not to raise huge red flags early. So in general, I would've preferred him to not say anything about risk until we actually get more numbers and real testing within our population. The average fatality rate hides the fact that this virus is very dangerous to the elderly.

Nursing homes and other long-term care units also have the lowest quality of care and staff ratings in the industry. Typically plagued by overstaffing, unhappy workers, etc.

I have to agree about the “risk is low” comment. It’s based on a snapshot in time. And besides the hand-waving about an evolving situation — well, it’s the evolving situation part that’s the risk.

I have a similar question. What percent of 70+ year olds that enter a hospital for cold/flu symptoms end up dying? Without knowing that as baseline, it is hard to meaningfully evaluate the covid19 death rate, especially considering that only the seriously ill are tested (and they don't report the death rate of those who test negative).

I can tell you that of 200,000 hospital admissions for the flu each year in the US, approximately 20,000 will die, i.e. 10%.

To put it another way, if we didn’t have extremely well established flu surveillance networks or even knew what the flu was, and people just started coming to the hospital with ILI and then dying, you would see 200,000 cases with a CFR of 10%.

But because we do have widespread, fast, and cheap testing we know that each year 30 million people get the flu and only about 1% go to the hospital, and 10% of those die, so the IFR is about 0.1%.

I'd really appreciate a citation, if you have one, so I can share this.

Actually it’s different every year. My numbers were apparently a mild year;



> CDC estimates that the burden of illness during the 2018–2019 season included an estimated 35.5 million people getting sick with influenza, 16.5 million people going to a health care provider for their illness, 490,600 hospitalizations, and 34,200 deaths from influenza (Table 1).

Around .5%

Thanks but no thanks for an uncited number.

In this study, about 9% of non-elective geriatric patients admitted to a hospital die. https://academic.oup.com/ageing/article/34/5/467/40349

In this study, it was closer to 15%. http://www.scielo.br/scielo.php?pid=S1807-59322009000700002&...

Now, if they only covid19 test people sick enough to be hospitalized, and if most of the deaths are over 70, shouldn't there be a comparison in the death rates to those patients testing negative?

Not all patients who enter a hospital are admitted for 3+ days.

Okay, so that means we need to ask what percent of flu patients admitted to a hospital are out in less than 3 days.

Probably not most of them?

Italy is seeing similar numbers if not worse.

This study makes a comparison of the age distribution in reported Covid-19 cases vs. the distribution of ages in the Chinese population. I think this approach can definitely provide insight however, there’s one assumption that this study uses which will definitely bias the fatality rates being estimated.

> We chose to fix to 100% the reporting rate of infected individuals that have symptoms and are aged 80 and more, and estimate the reporting rates in other age groups relatively to that of older individuals. If further data, coming from a study in the general population, shows that this assumption is violated, this would lead to an overestimation of the CFR in our study.

I find it hard to believe that 100% of cases in individuals over 80 will be reported. It seems like any estimation of fatality rate at this time is going to be guesswork without more systematic sampling of the population.

I’m not trying to minimize the danger of Covid-19. It seems like caution to prevent further spread is absolutely necessary.

Presumably age as a factor is used because it's easy to measure, but it would be nice to know the effect of comorbidity. For example, comparing otherwise healthy 60 year olds to otherwise healthy 30 year olds.

And a breakdown into specific medical factors. Diabetes, Smoker, AIDS, cancer, flu.

So all our presidential candidates (sitting or otherwise) have some relatively bad odds.

Iran's leadership is experiencing this right now.

> We estimated the age-specific case fatality ratio (CFR) by fitting a transmission model to data from China, accounting for underreporting of cases and the time delay to death. Overall CFR among all infections was 1.6% (1.4-1.8%) and increased considerably for the elderly, highlighting the expected burden for populations with further expansion of the COVID-19 epidemic around the globe.

It's worth pointing out that this is the CFR for the virus, SARS-CoV-2 (i.e. including asymptomatic individuals). The CFR for the disease, COVID-19, is 3.3% (2.9-3.8%).

I'm not sure which it is more common to report, but the 2% estimate that was used earlier in the epidemic was for the disease rather than the virus, apparently.

The CFR rate for the disease rather than infectius agent is not really useful for anything besides inciting panic. Consider the case where a virus only shows symptoms in 0.1% of case, but is 100% fatal when it does. You could report this as NEW EPIDEMIC 100% FATAL, WE ARE ALL GONNA DIE!!! but that hardly gives a realistic picture.

"We are all gonna die" is a statement about the mortality rate, not the case fatality rate. This paper does not deal with the mortality rate.

That CFR is not for the disease. It is for the disease that has progressed sufficiently to be recorded (noticed).

If I am reading it correctly, that is not what the paper says. It says that it takes into account the individuals who had the disease but were not reported/recorded.

Further to that, some individuals are asymptomatic which means that not only are they not reported, but they never are. They don't get the disease. It has nothing to do with how far the disease progressed in them, because they never have it.

Until the dust settles on COVID-19 this is all speculation.

I have a question about the Spanish Flu.

Most reliable literature CDC, WHO lost the CFR for the Spanish Flu at 2.5. This makes no sense to me.

The Spanish flu killed between 50-100 Million people, 3-6% of the world’s population, it infected about 500 Million people, so why isn’t the CFR between 10-20%?

How does the proximate cause of death factor into the CFR? In 1918, most of the deaths were from secondary infections:


As someone who is atopic but not asthmatic, I am especially concerned. My guess is that atopic and asthmatic indivdiduals might be at higher risk.

As someone in their forties, I can't think of any other potential risk that I am aware of where I might have a 1 in 50 chance of dying if I catch this (assuming an elevated risk) given that I am relatively health otherwise.

Do we have enough information to do this kind estimate for serious or critical symptoms, rather than just deaths? What are the chances of somebody in a given age bracket needing breathing support?

Death rate: Age 0-9: 0.0094% Age 10-19: 0.022% Age 20-29: 0.091% Age 30-39: 0.18% Age 40-49: 0.4% Age 50-59: 1.3% Age 60-69: 4.6% Age 70-79: 9.8% Age 80+: 18%

TL;DR dont infect ur parents as 60-69 has 1 in 21 chance of death.

I’m at Ground Zero in the US (King County, on the East side is Seattle), where about 10% of the reported cases are dead. I’m your parents’ age, in the 1.3% cohort.

Gotta admit, it’s scary. One death took place in the hospital where I had a checkup, on the day of the checkup.

CMIIW: The same way age segments the CFR, so does smoking, existing conditions, etc. So if you're <40, not a smoker, no existing disease, the risk is even lower.

Having said that, it's still a bad situation, since getting infected increases the likelihood of others getting infected and dying, including people in higher CFR brackets. This is not like "getting cancer" or "getting hit by lightning", because there one person getting it doesn't affect the probability of another getting it.

Really please don’t infect _anyone_, as it increases the likelihood that someone else’s parent or grandparent will die.

Thanks for summarizing.

Plenty here are going to have parents in 70-79 (like I do) or 80+. And I really don’t like those odds.

These numbers may look insignificant but your base chance of dying in a given year is on a similar order. Have a google for life tables, the UK ones are available online.

For younger people, it's like having a fair part of a year's worth of life risk, for older people several years.

Do you want that risk for no benefit? There's also whatever problems you get that don't kill you. I suspect you waste a good few weeks of your life regardless of whether you survive.

Do you have a link for that? The first result I got is this life table for US 2003 on Wikipedia (https://upload.wikimedia.org/wikipedia/commons/4/47/Excerpt_...), and the risk for an average 60 year old is around 1% per year. Do you mean to say 1% and 4.6% are on a similar order?

Of magnitude, yes. This is not the one I found yesterday but figures are similar.


That's not reasonable. 1% risk of death vs (1+4.6)% risk of death (a) is closer to 1 order of magnitude higher (log_10(5.6)=0.75), and (b) 1%/year and 5.6%/year are nowhere near the same the way most normal people think about the risk of dying.

A 1 order of magnitude lower risk (0.1%) is basically negligible, like a regular flu. On the other hand, a 1 order of magnitude increase, i.e., around 10% risk of dying would already rate among the deadliest epidemics in history, and far above things like the Spanish flu, so comparing orders of magnitude is just not the right way to think about this number.

You might have a point there. But I think a lot depends on the error of the disease estimates, and it seems clear that they could well overlap with the range of natural death rates. Dependent on how you slice and dice it.

For sure old people are at at least a year's risk.

I wouldn't gamble with a 1 in 500 chance for me either.

That works out to 2000 micromorts, which compares to the accumulated baseline risk over 3 months of living: https://en.m.wikipedia.org/wiki/Micromort

Yes, bit more dangerous than BASE-jumping. No, thanks. When was the last time you did something that had 0.2% chance to kill you?

Also what this number kind of glosses over is how are the survivors doing. Half of those that get ARDS have life-long consequences. There are still 20.000 active cases in China, 1 month after the epidemic peaked there.

EDIT: I took BASE jumping risk from here http://www.wingsuitfly.com/risk/4572000812 not from the wiki reference

That's also the risk without some major reward. If you want to do base jumping you're trading that risk for an exhilarating experience at least.

Yeah but the report doesn't talk about the degradation in quality of life you'll have to endure if you survive. It may take you months/years to fully recover.

As a 30-something 2000 micromorts is like my entire yearly micromort budget. I mean, I wasn't seriously worried about dying in 2020 but risks over 1,000 micromorts are worth treating as a serious deal even if you shouldn't be terrified of them.

I still wouldn't want to get infected.

As with any statistical analysis based on a sample of the total population, there will be biases (as many have already noted). That being said, these results reflect what we’ve seen in the real world in places like Washington state, Italy, Iran, and even S. Korea. More to the point: these data underscore the importance of following the advice of public health officials.

It’s fine to have an intellectual discussion about the merits of the study, but let’s make sure that we keep our eye on the prize. Each of us has a responsibility to do our part in protecting our parents, friends, and coworkers.

TL;DR - This study suggests that many of us on HN will be fine no matter what. But it also demonstrates that, if left unchecked, it’s possible (if not probable) that many of us will be grieving the loss of someone we love. There’s no need to panic, and there’s no room for those who seek to be dismissive, flippant, or ignorant. Everyone will be fine if each of us focuses on doing the right thing.

why is the CDC not telling us where are the suspected cases and how many out there??? Do they even know that number??

Death rates aside, it looks like younger people are less likely to even get the disease (not especially surprising). If you exclude the really young people, even the 30 year olds would likely be under represented (I think). One implication of this may be that societies with more socially engaged older people will be more vulnerable to this. E.g. countries where people who serve as frequent touch points to strangers like frontline retail jobs are likely to be older might do worse in this circumstance.

Are we sure they don't get it, or are just asymptomatic in the short term.

Chicken pox is a thing parents commonly seek out for their kids around here. But in the long term the vaccine is still better at reducing long term consequences.

(Got it intentionally as a child then again [unintentionally] as a teen. Had some nerve damage since. Not looking forward to shingles.)

That was my point of confusion on the charts for symptomatic people. I’m assuming that the relatively high rates of non symptomatic individuals implies they’re testing people without symptoms in a somewhat random sample style

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