
Substantial undocumented infection facilitates rapid dissemination of SARS-CoV2 - mcone
https://science.sciencemag.org/content/early/2020/03/13/science.abb3221
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nmca
Does this mean the mortality rate is, approximately, 10x less than currently
estimated?

(86% of cases unreported, eg about 1 in 10 reported, assume that number of
unreported fatal cases is 0)

Edit: closer reading suggests the optimism is sadly unwarranted, the headline
under-reporting number of 86% is from the early pre-travel ban model, post-
travel-ban estimates give a 65% detection rate, combined with the increased
number of cases in this later period this implies that naive mortality
estimates are more like 2x off than 10x off.

~~~
httpz
Assuming that someone who died from coronavirus is far more likely to have
been tested for the virus than someone who's been infected by it, the true
death rate of someone infected by the virus is probably far lower than the
calculated death rate. (# of confirmed death / # of confirmed infections).

S.Korea did extensive testing, which reduces the number of unreported
infections. So the calculated death rate in S. Korea is 4x lower than a
comparable country like Spain, which has similar # of confirmed cases,
population, GDP, and GDP per capita.

If we assume S. Korea's calculated death rate(<1%) is closer to the true death
rate and apply it to other countries to derive the total # of infections
(reported + unreported) based on the reported death count, we can see there
may be far more infections than we know.

~~~
cycrutchfield
This is not really valid due to fatality rate being heavily dependent on age,
comorbidities, and healthcare quality (which is itself dependent on case
load), and the distributions of these differ greatly across countries. But,
sure, you could try to normalize these to infer the actual case load.

~~~
TheOtherHobbes
It would be useful if this could be broken down into separate categories -
estimated CFR without medical intervention, and likely CFR at various levels
of intervention.

The former suggests what your population mortality rate will be if your
healthcare system is overwhelmed, and could possibly be derived from Italian
data. The latter gives you a resources vs effectiveness sweet spot that
maximises health system throughput, so you can save the maximum number of
lives over time given the resources you have (or can build/find.)

The age profile is relevant, but worryingly there seem to be a number of
reports that it's not just the over-65s who are at risk.

I haven't seen anything more recent about this than the Chinese estimates from
a month or so ago.

~~~
wahern
CFR can't be used to determine population mortality rate. It in no way
reflects r0, and only tangentially at best hints at percentage of asymptomatic
infections (and that's recent as there was never drive-by testing for any
previous epidemic). Those two dimensions add unfathomable complexity to the
equation. In many ways it's better to leave those dimensions out to improve
the utility of CFR. A doctor doing triage or health department coming up with
orders wants a simple, basic number, not a panoply of options that require
data they won't have at hand.

We by all means should collect more data, just don't shoehorn it into such a
very primitive yet very essential statistic. Give them new names and new, more
appropriate semantics. I suspect that after this is over they're going to
tighten the criteria around CFR, and in particular exclude by definition
asymptomatic cases and possibly non-hospitalized cases. They never had to do
that before as "cases" usually implied someone sick enough to be given a
diagnosis, which in turn implied someone at least moderately sick--e.g. actual
or suspected case of pneumonia.

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joe_the_user
The article is interesting but it seems to be just a mathematical model rather
than a biological study actually finding and studying people who had
undocumented infections.

I know they have found people like that but I'd still be leery about going
from data to a pronouncement since I assume the data just isn't extensive or
reliable.

~~~
gwbas1c
But you need actual testing in order to get real data

~~~
Taek
South Korea has done a good job of getting enough tests done to have
meaningful data

~~~
iso947
Self selecting tests. Need the types of control data that polling companies
use.

~~~
akiselev
South Korea has been doing extensive contact tracing and quarantining from the
start. They're as close to a statistical sample as we're going to get until
large scale random antibody tests are done. At best the US could probably fit
it into the census process.

~~~
spookthesunset
Until you get a good bit of random antibody tests, it is all speculation.
Nobody really knows how widespread this thing is, what its actual death rate
is or anything else.

I personally wouldn't be surprised to learn the number of people who had it or
have it now is hundreds of times higher than the "confirmed cases". I would
also speculate that this virus has been in wide circulation for months now.

But my guess is as good as anybody else. Until we get actual, statistically
valid high quality data.... all we have is speculation. I sure hope we are
making the right call shutting things down as much as we are. People have to
remember that there are serious physical health consequences to the actions
being taken. Suicide rates will climb, alcoholism & addiction will jump, crime
will go up, etc.

A few weeks of this kind of economic pause is one thing but at some point in
the very near future people are going to want to know what the end game is.

~~~
drivebycomment
As of today, Korea reports 274K tested, with 3.2% infected out of that. They
also show strong signs of containment. Those two datapoints indicate that they
didn't miss many infected cases.

~~~
spookthesunset
Does that testing include people who had it before and just have antibodies?
Or just active cases?

~~~
dboreham
There is no deployed serological test at present.

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taeric
This feels mixed. If true, it is more than just explaining how rapidly it
spread, as the spread happened months ago. It also raises the question of why
is it so severe some places, but less so many others?

~~~
alkonaut
How did it spread long ago without killing a lot of elderly people back then,
raising suspicion?

Perhaps elderly people often trickle in to ICUs with respiratory issues and as
long as it’s flu season no one really notices some more dying 80+ people
especially as there was no test for this virus?

~~~
tathougies
> Perhaps elderly people often trickle in to ICUs with respiratory issues and
> as long as it’s flu season no one really notices some more dying 80+ people
> especially as there was no test for this virus?

I imagine most countries keep track of flu deaths and would have noticed an
uptick.

~~~
SpicyLemonZest
I want to make it absolutely clear that I am not minimizing the coronavirus
here, but the statistics would be lost in the noise. If known statistics are
an order of magnitude too low, and there have actually been 800 deaths in the
US instead of 80, that's still only about 3% of the total flu deaths this
season. And flu seasons vary in intensity by a lot more than 3%.

~~~
taeric
This is my line of thinking, too. And I second your point of not trying to
minimize it, but there appears compelling evidence this is already hit. Trying
to determine what I could watch to get more or less confidence in this view.

~~~
tathougies
If coronavirus has already hit America then that is a huge vote of confidence
for the American medical system, which, in this hypothetical, has managed to
deal with a major pneumonia pandemic without so much as calling in extra
nursing shifts. That would suggest that America's medical system is ahead of
Italy, which is suffering heavily due to running out of hospital space.

~~~
taeric
Not necessarily. My contention is that in places with many severe cases, there
are also tons of mild cases. In particular, I see no reason to think the young
population is not getting it. Toddlers and pre teens. Especially in areas with
higher family residence.

So, my hypothesis centers around trying to give an explanation for why that
population isn't impacted by severe cases. Going off how bad it hit me, _if_
that is what hit me, best I have is lung health. And I don't have unhealthy
lungs, all told. I do, however, have a distant history of asthma, and I find
it plausible it did damage my lungs long ago.

To flip it some. They say even if you survive, you may have lasting lung
scarring. What if that preceded the covid?

~~~
tathougies
> To flip it some. They say even if you survive, you may have lasting lung
> scarring. What if that preceded the covid?

That doesn't make sense. Covid follows the same exponential curve in all
countries. If the US has a bunch of latent infections, but no huge surge in
pneumonia, then that would imply there is something special about Americans
that keep them from developing the worst symptoms, or something special about
American old people that, despite contact with the young silent carriers, they
do not develop the disease. There is no reason to believe either of those are
true.

They say we are a week or so behind Italy. Italy is experiencing hospital
overruns. If the week-behind estimate (based on actual numbers) is overly
conservative, then we would have expected to see hospital overruns in the
United States from old people with pneumonia. However, we don't have that.
Thus, if the week-behind estimate is overly conservative, we are certainly not
at the same point as Italy or ahead of Italy, so we can say that we are
anywhere from 1 week to 1 day behind Italy which is still a pretty good bound.

~~~
taeric
That is exactly what I'm asserting. That places not having a surge in severe
cases are different than the places that have had a surge. That is literally
my hypothesis.

The week behind curve on Italy is one to watch. My assertion is that we have
had infections hitting here for at least a month. Probably longer. If we don't
get the same severe case spike in a week, will everyone just keep upping their
models? Because that is what it looks like people are doing.

