
Coronavirus: Santa Clara County has had 50 to 85x more cases than we knew about - timmytokyo
https://www.mercurynews.com/2020/04/17/coronavirus-2-5-to-4-2-of-santa-clara-county-residents-infected-stanford-estimates/
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dilippkumar
Balaji Srinivasan had a medium post about this:

[https://medium.com/@balajis/peer-review-of-
covid-19-antibody...](https://medium.com/@balajis/peer-review-of-
covid-19-antibody-seroprevalence-in-santa-clara-county-
california-1f6382258c25)

A summary of his post:

1\. There were 2 false positives in 401 pre-covid samples (known negative).
Assuming a normal distribution, 2 sigma confidence can account for up to 80%
of the positive results reported in this study.

2\. For the virus to have already infected this many people, it should’ve
spread so fast that it doesn’t match what we know about similar epidemics.

3\. The researchers recruited volunteers via facebook ads. There could be
sampling bias here.

I encourage everyone to read the article: my summary < The original article.

~~~
Gibbon1
My summary is when betting on any test with a low positive rate take under not
the over.

Saying at least this many people have been infected, wrong. Better. At most
this many people have been infected.

Reminds me of a survey 15 years ago that said something like 2-3% of black
people approved of the job the president was doing. That 2-3% was more likely
'rectified noise'.

~~~
SpicyLemonZest
In normal times, where there aren't critically urgent decisions to be made,
that's the right approach. We don't have that luxury right now; we're
continually charting the path forward, and if we don't have clean data then
we'll need to chart it with unclean data.

And I think it's hard to argue that this study is worse than our _existing_
case data, which is simply a daily aggregate of the number of new positive PCR
tests labs report they've run. That's not even attempting to be a
statistically valid estimate.

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skybrian
Preprint is here:
[https://www.medrxiv.org/content/10.1101/2020.04.14.20062463v...](https://www.medrxiv.org/content/10.1101/2020.04.14.20062463v1.full.pdf)

You should read what they have to say about the study's limitations before
concluding too much. It's not a random sample (though they tried to correct
for this), and the test is new, so their estimates of the test's accuracy are
uncertain.

Main discussion is here:
[https://news.ycombinator.com/item?id=22899272](https://news.ycombinator.com/item?id=22899272)

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xt00
It will be really interesting once large random samples of people are tested
-- quite possibly we will find out that the virus was spreading super widely
in certain areas for Jan / Feb / March before lockdowns started happening..
the model might end up being something like given X person has the virus, what
is the likelihood that they will interact with somebody over the age of 60..

~~~
BubRoss
I don't know why this was downvoted, it seems reasonable to me. A lot of
people would have traveled for christmas, new years and chinese new year.
Testing was almost non existent. I would bet that everyone by now at least
knows someone who suspects they have already had it.

~~~
sfj
Because mapping out the geographic locations of those who were infected could
hurt the economy of the blighted areas even further.

~~~
BubRoss
Why would that be true? This is talking about antibody tests and is likely
indicative of statistics and patterns common to everywhere else.

~~~
sfj
> quite possibly we will find out that the virus was spreading super widely in
> _certain areas_

Emphasis mine

~~~
BubRoss
Why would it be spread in certain areas and not others? Why would knowing who
has antibodies hurt the economy when everyone is already secluded?

~~~
sfj
> Why would it be spread in certain areas and not others?

I would guess because of different social distancing practices.

> Why would knowing who has antibodies hurt the economy when everyone is
> already secluded?

Knowing who has antibodies is going to be conflated with who has covid-19,
because the general public is not going to get the nuance. And everyone is
secluded _right now_ but that will change.

However, I don't understand why you are asking me to prove the premise of the
parent poster. I thought I was answering the question why he might have been
downvoted, not whether what he was proposing was _feasible_. Maybe you could
explain why you are asking me this. It seems you agree that a map targeting
certain groups of people as likely of having covid-19 would be a bad outcome,
isn't it? If so, you could probably understand why he might be downvoted.

~~~
BubRoss
To be clear, you think that enough people will be paying attention to this
study on testing for antibodies that it will hurt the local economy of the
place being tested, because the people paying attention don't understand
antibodies?

~~~
sfj
What “study”? Are we not talking about what the parent poster wrote anymore?

And to answer your question, you see, there are these people called reporters,
and they get a lot of information from very different sources. They filter out
what is interesting and broadcast it to their audience. Perhaps you've heard
of them.

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twitexplore
What is the peer review and publication status of this study?

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onlyrealcuzzo
Can you be pre-symptomatic and have antibodies?

~~~
SpicyLemonZest
It's unlikely. I don't think we know the exact progression enough to say for
sure, but typically the specific immune response won't start that quickly. (It
couldn't account for anything close to the study results in either case -
there's no realistic way that there are 50x-85x cases that are about to become
symptomatic soon.)

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hatenberg
Let's all remember this when peopel accuse china of cooking the numbers

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Techies4Trump
I was wondering why it took so long for a simple random sample study to be
done, but finally it has been done, and the result is pretty much as I
expected - millions are carrying the virus, making the true mortality rate
tiny.

This looks like a reliable study since its testing for antibodies, rather than
the more common swab tests.

~~~
gnulinux
If the true mortality rate is tiny, how did this virus manage to kill 153k
people in 3 months? Can someone ELI5 me that? People have been saying "Flu
kills 30k Americans every year" and now 30k Americans died of this disease in
3 months AFTER locking up the entire country. Something doesn't add up.

~~~
rogerkirkness
If the most vulnerable did not have flu shots, the mortality of the flu would
be shocking. You may or may not need one (or notice if you didn't) but every
high-viral-load-facing healthcare worker, cystic fibrosis patient, etc. gets a
flu shot like clockwork. And while they don't always work, they mostly work,
and that hugely reduces mortality. The problem with this one is the novelty.
Human immune systems get better trained (not necessarily better) with age.
Cytokine storms in the eldery with covid-19 is the biological equivalent of an
overfit AI with memory leaks that runaway. If the R0 turns out to be 5.6,
basically everyone has been exposed at this point (not necessarily infected).

~~~
gnulinux
Is it usual to see healthcare workers dying of flu as well, like they do with
COVID due to high viral load?

~~~
redis_mlc
> Is it usual to see healthcare workers dying of flu as well, like they do
> with COVID due to high viral load?

SARS-1 (2002/2003) wiped out ICU staff in both Toronto and S. Korea.

"High viral load" is an undefined term, so I won't comment on that.

