
Preliminary result of the Gangelt, Germany Covid-19 case cluster study [pdf] - chvid
https://www.land.nrw/sites/default/files/asset/document/zwischenergebnis_covid19_case_study_gangelt_en.pdf
======
gwd
Paper is short so worth reading, but some key points:

* They had an outbreak in this village as a result of a festival event in mid-February

* A random sample of 1000 from a population of 12,000 were sampled afterwards

* The immunity within the population as a whole was at about 15%.

* The fatality rate was 0.37%

It's got this statement:

> By adhering to strict hygiene measures it is to be expected that the virus
> concentration of an infected individual can be reduced to the point that the
> illness manifests more mildly, with simultaneous development of an immunity.

But it seems like the that statement is just an assertion, not something
specifically supported by the data they gathered in this study, because it
goes on to say:

> These favourable conditions are not present in a superspreading event (e.g.
> Karneval meeting, apres-ski bar in Ischgl, Austria).

~~~
tinus_hn
These statements are so odd they look like a translation error. Is there a
German version of this paper?

~~~
luspr
Yes. Same url just drop the "_en":
[https://www.land.nrw/sites/default/files/asset/document/zwis...](https://www.land.nrw/sites/default/files/asset/document/zwischenergebnis_covid19_case_study_gangelt.pdf)

~~~
tinus_hn
The statements are similar so they are stating this community went through the
worst case scenario and ended up with 0,37% fatality.

~~~
dr_zoidberg
If that mortaility rate is common, it would mean there are ~10x (or more)
infected in the world...

This sort-of coincides with the large asymptomatic reports. So what do we do
from here on? Such numbers would surely raise the famous r0 infection rate,
and it means this is far more contagious than reported/believed.

~~~
raphaelj
r0 can stay the same, it can just means that the epidemic "took off" earlier
than what our tests show.

------
timkam
Isn't this the report of the case study that was discussed with much
controversy in German media, in particular because the researchers hired a
high-profile marketing agency for promotion and held a press conference
together with the prime minister of the federal state (NRW) before subjecting
the findings to the scrutiny of the scientific community?

Edit: link to newspaper article (German):
[https://www.sueddeutsche.de/gesundheit/heinsberg-studie-
coro...](https://www.sueddeutsche.de/gesundheit/heinsberg-studie-
coronavirus-1.4876474) Note that Gangelt is a municipality in the Heinsberg
district, so the article and the report refer to the same study by different
names.

~~~
luspr
However, the "controversy" has been overstated by the German media as well.
Drosten, virologist who has been cited as one of the critics, called the
Gangelt/Heinsberg study "very solid and robust" just yesterday:
[https://www.zdf.de/politik/maybrit-illner/christian-
drosten-...](https://www.zdf.de/politik/maybrit-illner/christian-drosten-lobt-
gangelt-studie-extrem-solide-und-robust-aus-sendung-
vom-16-april-2020-100.html)

Particulary, the death rate will be close to the estimate.

~~~
sokols
He also said that "..the data on the German town are definitely not
representative for the country".

[https://twitter.com/c_drosten/status/1251034050883657729](https://twitter.com/c_drosten/status/1251034050883657729)

~~~
s9w
The thing is that it's simply not exactly stated what kind of population they
tested. Whether they were representative of that town or the German
population. Of their sample was actually representative of the German
population (which I heavily assume since they talked a lot about that) then
the results will be quite robust.

~~~
pintxo
How would you create a representative sample for the whole population if all
your samples are from a sub-population with a known cluster of cases?

~~~
s9w
The cluster thing is obviously hard to remove. But the population.. that
should be very doable. You'll just have to adjust the people you chose
according to the general population. Not sure exactly how that goes down in
practice. But in the press conference he stressed multiple times how this was
representative and was done in cooperation with statisticians etc.

~~~
pintxo
Problem here comes from the question "representative for what"?

I can easily see this to be representative for the town in question.

But I find it quite obvious that it cannot be representative for the whole
country due to the initial difference in exposition.

~~~
s9w
Yeah well but is that really important? If they nail the same sample age-wise
etc and use that to calculate lethality, then that number can be used on the
general population, right? The only difference left is the rate of infection.
But how many of those died should be the same.

~~~
mannykannot
I would guess that the spread of the disease and the rate of infection could
be parameters to consider in planning policy for the immediate future. On the
other hand, could this result be used to usefully estimate the total values in
other regions from the hospitalization numbers?

------
Tepix
There is a large number of asymptotic cases which is quite encouraging.

In their preliminary conclusion they write:

" _By adhering to strict hygiene measures it is to be expected that the virus
concentration of an infected individual can be reduced to the point that the
illness manifests more mildly, with simultaneous development of an immunity._
"

I wonder how they came to that conclusion. It would be great if it turns out
to be correct.

~~~
point78
So wash your hands and gargle and your symptoms are mild?

~~~
rooam-dev
Interesting indeed, perhaps by reducing the quantity of virus we give more
time to our body to prepare for the "invasion"?

~~~
gwd
I've heard that as well. Basically, the spread of the virus inside your body
is exponential too, whereas the immune system's response time will be fairly
static. So if you're exposed to a little, the immune system has time to
respond before the infection gets out of control; if you're exposed to a large
amount, by the time the immune system starts to respond, the virus is already
widespread in your system.

~~~
maxerickson
Why wouldn't it be the other way around? If the virus replicates very fast,
people with minimum infectious doses have a couple replication generations of
extra time.

If the virus replicates more slowly, a large infectious dose would have the
same impact as multiple replication generations.

I'm not asserting the above is what happens, I'm asking the question.

~~~
kortex
Viral load V, dV/dt = rV. This loosely solves to V = a*exp(rt). The bigger
your V0, the faster the initial rate of increase.

The Vmin to be detected by your immune system is small. You want the most time
between Vdetected and Vdanger.

~~~
maxerickson
My question is about how much r matters.

For influenza, each infected cell apparently infects ~22 other cells:

[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1563736/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1563736/)

So in 2 generations you have 500x the virus.

If it were 'less' exponential, and each cell only infected, say, 5 others,
then you get to 500x late in the 4th generation.

In a cartoon example where a low exposure leads to 1 infected cell and a high
exposure leads to 500 infected cells, the low exposure matters more if the
reproductive factor is lower.

------
danieltillett
There are so many unknowns from this report that it is hard to make much from
it. Some of the major questions.

1\. How many people in this town ended up in hospital? How many are still in
the ICU and likely to die?

2\. Is the population sero tested representative of the town population? Was
this population sampled biased by those who had obvious symptoms being more
likely to participate?

3\. Are the 15% positive representative of the German population or is it
skewed to the young?

4\. How was the accuracy of the serology test determined? >99% is impressively
accurate if true.

~~~
netjiro
> "(anti SARS-CoV2 IgG positive, specificity of the method >.99%)"

This is a misprint. They meant to say 0.99 or 99%, not .99%

That means it's very reliable that any positive signal originates from covid19
antibodies, instead of from _something else_.

That does not mean that it's 99% accurate with regards to sensitivity.

~~~
cowmoo728
Preliminary data from China suggests that a non negligible percentage (maybe
5%) of recovered patients never produce the neutralizing antibody.

[https://www.medrxiv.org/content/10.1101/2020.03.30.20047365v...](https://www.medrxiv.org/content/10.1101/2020.03.30.20047365v1)

This would mean the antibody test alone cannot tell the full extent of
community spread. There's a brief summary of antibody knowledge here.

[https://www.the-scientist.com/news-opinion/what-do-
antibody-...](https://www.the-scientist.com/news-opinion/what-do-antibody-
tests-for-sars-cov-2-tell-us-about-immunity--67425)

------
postingawayonhn
Not everyone is convinced that this study is accurate.

 _" It is important to understand the sensitivity and specificity of the
serological test used in the German studies to be sure the test is not picking
up antibody to other corona viruses (4 different common cold causing
coronaviruses have been isolated in humans during the past years and 3 more
serious ones (SARSCoV1 and 2, and MERSCoV)."_ [1]

It would be good to see more of these studies conducted in different areas by
different teams to see if they come to similar conclusions.

[1] [https://www.sciencemediacentre.org/expert-reaction-to-
unpubl...](https://www.sciencemediacentre.org/expert-reaction-to-unpublished-
preliminary-findings-looking-at-the-presence-of-antibodies-to-sars-
cov-2-virus-in-residents-of-gangelt-in-germany/)

------
ImaCake
This monograph points to an IgG antibody assay with >99% specificity which
means the false positive rate is tiny. Can anybody tell me if there is a
commercial antibody test for Covid19 that advertises anything close to this?

My thought is that they have done this with an ELISA. Using a commercially
available (or custom made) antibody instead of using one of those terribly
inaccurate chromatography strips.

