
South Korea reports recovered Covid-19 patients testing positive again - abhiminator
https://www.reuters.com/article/us-health-coronavirus-southkorea/south-korea-reports-recovered-coronavirus-patients-testing-positive-again-idUSKCN21S15X
======
merricksb
Same topic discussed yesterday:

[https://news.ycombinator.com/item?id=22820421](https://news.ycombinator.com/item?id=22820421)

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drocer88
Key passage from the text:

Kim also said patients had likely “relapsed” rather than been re-infected.

False test results could also be at fault, other experts said, or remnants of
the virus could still be in patients’ systems but not be infectious or of
danger to the host or others.

“There are different interpretations and many variables,” ...

~~~
_wldu
Many of the COVID tests are not cleared/approved or even authorized for
emergency use yet. But, this is what we are having to rely on to count
confirmed cases due to the circumstances.

[https://www.questdiagnostics.com/dms/Documents/covid-19/SARS...](https://www.questdiagnostics.com/dms/Documents/covid-19/SARSCoV-2_Patient_Fact_Sheet.pdf)

 _" Is this test FDA-approved or cleared?

No. This test is not yet approved or cleared or authorized by the United
States Food and Drug Administration (FDA). When there are no FDA-approved or
cleared tests available, and other criteria are met, FDA can make tests
available under an emergency access mechanism called an Emergency Use
Authorization. Quest Diagnostics is working with FDA to obtain Emergency Use
Authorization."_

And the tests that are authorized for emergency use are not FDA cleared or
approved.

 _" Testing was performed using the cobas(R) SARS-CoV-2 test. This test was
developed and its performance characteristics determined by LabCorp
Laboratories. This test has not been FDA cleared or approved. This test has
been authorized by FDA under an Emergency Use Authorization (EUA). This test
is only authorized for the duration of time the declaration that circumstances
exist justifying the authorization of the emergency use of in vitro diagnostic
tests for detection of SARS-CoV-2 virus and/or diagnosis of COVID-19 infection
under section 564(b)(1) of the Act, 21 U.S.C. 360bbb-3(b)(1), unless the
authorization is terminated or revoked sooner."_

~~~
pmoriarty
On the subject of unreliable tests, here's a transcript of a letter read on
episode 588 of _This Week in Virology_ [1]:

 _I 'm an infectious disease doctor and would like to point out an important
factor in diagnosing this infection (and all respiratory pathogens that use
nucleic acid probes for specimen collection). This is of particular concern
now that China has transitioned to a much more problematic clinical diagnosis
based more on clinical symptoms than PCR testing._

 _While it may seem trivial how a health care worker jams a swab in to someone
's throat or nose, technique is important. If anterior naries (front of nose)
swabs or side of mouth swabs are done, rather than the true posterior
nasopharynx or oropharangeal swabs, the sensitivity drops dramatically._

 _We have shown this to be true repeatedly with diagnosis of influenza and
respiratory pathogens, and I am disappointed that it has not been mentioned
more in discussions about the PCR tests, missing the diagnosis in people who
are positive and negative then positive again._

 _We often see people admitted from the ER with the perhaps carelessly
collected flu test who miraculously are flu positive by the time they are
admitted. Like so many cultures and diagnostics in infectious diseases,
specimen collection and handling is critical._

 _I warn my patients about the unpleasantness of a nasopharangeal swab and
jokingly tell them that if it doesn 't cause a wincy-face reaction we haven't
collected specimens from where the viruses reside._

[1] -
[http://www.microbe.tv/twiv/twiv-588/;](http://www.microbe.tv/twiv/twiv-588/;)
at about 1 hour and 38 minutes in

~~~
macintux
I had one of those nasopharyngeal swab tests conducted about a month ago for
the flu. It was extremely unpleasant, so I can concur with the good doctor,
albeit astonishingly brief.

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ceejayoz
Do we have any data on South Korea's tests and their false positive/negative
rates? Even a couple percent would lead to several cohorts of "tested positive
but weren't" and "tested negative but still were actually positive", I'd
think.

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Nav_Panel
Where's the study and data? What's the time frame we're looking at here?

This German study
([https://www.medrxiv.org/content/10.1101/2020.03.05.20030502v...](https://www.medrxiv.org/content/10.1101/2020.03.05.20030502v1)
\-- see the graphs near the end of the PDF) suggests that viral RNA may be
detectable in recovered patients for 3 weeks after symptom onset, or longer
(the study seemed to stop testing after 3 weeks, despite some recovered
patients still testing positive for viral RNA). But they were unable to
isolate _live virus_ after about a week post-onset.

Could this be what we're seeing?

If you're still worried, I recommend looking at this small study on macaques
designed to test immunity
([https://www.biorxiv.org/content/10.1101/2020.03.13.990226v1](https://www.biorxiv.org/content/10.1101/2020.03.13.990226v1)).
They found that the macaques did develop immunity and were able to fight off
the virus on reinfection. If we compare with the this study
([https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2851497/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2851497/))
on the development of immunity in response to the original SARS virus (I'm not
sure on the exact mechanism of immunity, but if the body's immunoglobulin
response targets the spike protein, then it's probably similar), we should
probably expect antibody production to continue at least a year after
infection, if not for 3-4 years after.

------
jrockway
What is our plan if Covid-19 doesn't go away after you recover from an
infection?

~~~
12yrprogrammer
No politician wants to say it, but the plan regardless was to quarentine until
a vaccine comes out in 1 or 2 years.

That or accept the 0.5 percent death rate with the "flatten the curve" method
where we all catch it.

Your concern means we'd only have situation 1, quarentine for 1 or 2 years.

~~~
SpicyLemonZest
Note to readers that there's been a flood of new accounts like this one, whose
first and only comment is "haha we'll be in quarantine for 2 years". This is
the third one I've noticed in the past 2 days. Either it's a popular troll or
someone's making a concerted effort to manipulate the discourse; in either
case I think it's important not to take this seriously.

~~~
dang
Please don't post this sort of insinuation of astroturfing. There's a site
guideline specifically against it:
[https://news.ycombinator.com/newsguidelines.html](https://news.ycombinator.com/newsguidelines.html)

The reason is that people are far too quick to leap to this interpretation,
and since we have next to no data about each other from HN posts, pretty much
every divisive topic gets drowned in such insinuations if allowed to.

Lots more explanation here:
[https://hn.algolia.com/?query=by:dang%20astroturf&sort=byDat...](https://hn.algolia.com/?query=by:dang%20astroturf&sort=byDate&dateRange=all&type=comment&storyText=false&prefix=true&page=0)

~~~
SpicyLemonZest
Sure, I'll refrain, but I hope you're taking into account that these kinds of
astroturfed comments are causing significant harm.

~~~
dang
Sure you'll refrain, but then you do it again in the same sentence? That is
not cool.

------
robocat
The issue is talked about at 7:59 in this video
[https://youtu.be/gAk7aX5hksU](https://youtu.be/gAk7aX5hksU) (Leading COVID-19
Expert Professor Kim Woo-joo from Korea University Guro Hospital)

------
emersion
The article doesn't make it clear how many such cases there are:

> The South Korean figure had risen from 51 such cases on Monday.

> "The number will only increase, 91 is just the beginning now"

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gnulinux
Layman here. Curious: if this is true, that you don't gain long term immunity
to SARS-2 by catching COVID, would that have any implications on potential
vaccine in the future? Does this mean, this virus is something we cannot build
a vaccine for? Does this mean even if we have an approved vaccine, it would
likely have a very low probability to protect us? Or do RNA vaccines work in a
way that affects our immune system that's entirely different than how immune
system builds immunity against the virus itself?

~~~
ping_pong
There was an experiment done a few weeks back where they infected rhesus
monkeys with SARS-CoV-2 and the monkeys were subsequently immune. So the idea
that we humans don't get some amount of immunity would be hard to believe.

[https://www.biorxiv.org/content/10.1101/2020.03.13.990226v1](https://www.biorxiv.org/content/10.1101/2020.03.13.990226v1)

------
RyanShook
Isn’t the concept of someone being reinfected with the exact same virus
basically unheard of?

~~~
pcr0
No, herpes, chickenpox + shingles would be the counter examples.

~~~
nkohari
In my understanding, herpes and varicella (chicken pox/shingles) are thought
to be "reactivations" of dormant viruses, not reinfections. The virus is never
fully eliminated, and sometimes it becomes re-activated.

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jliptzin
Could this turn out like HIV where there is an initial infection period
followed by some dormant period and then another period where it causes more
problems for the host again?

~~~
SpicyLemonZest
It's unlikely. Coronaviruses are well-known and well-studied, so we can be
pretty confident that the disease will just be a single respiratory tract
infection rather than anything weirder.

------
angel_j
I feel like we're about to learn way more about viruses than we thought we
knew. It's like how NYTimes "scientists" only recently learned that gut
bacteria is our friend...

