Preliminary result of the Gangelt, Germany Covid-19 case cluster study [pdf]
land.nrw
land.nrw
* 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).
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.
Edit: link to newspaper article (German): https://www.sueddeutsche.de/gesundheit/heinsberg-studie-coro... Note that Gangelt is a municipality in the Heinsberg district, so the article and the report refer to the same study by different names.
Particulary, the death rate will be close to the estimate.
https://www1.wdr.de/nachrichten/landespolitik/heinsberg-prot...
That doesn't mean that you can't learn anything from this study for the rest of the country, just that you can't extrapolate it naively.
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.
Takeaway: death rate is lower than many initially feared. But it is not like we have already 15 % immunity. In reality it is probably around ~1-2% based on the number of deaths.
It is bit sad as it seems to be powerful study and given the attention to the subject, publication of priliminary results are perfectly in order.
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.
If not, then is this a well-established feature of respiratory virus infections?
In other words, to what extent is this claim backed by evidence? And is it evidence from studying C19 specifically?
How could you proxy for viral load? And more specifically: How reliable can this measure be?
So short answer: To a degree yes, but unlikely that it is a reliable finding.
Insert super low load, stay home for two weeks, and you have been immunized.
Instead we could grow lots of viral particles. Irradiate them to certain death. Then use it to repeatedly challenge the immune system over a long period. Very expensive and nowhere near as effective or reliable as a proper vaccine, but would induce some level of resistance in a fraction of the population.
If true, would it be possible to infect yourself with a tiny concentration of the virus, then isolate, and expect mild illness followed by immunity?
[1]: https://www.newscientist.com/article/2238819-does-a-high-vir...
No studies have looked at various levels of initial dose (does initial dose correlates to viral load?) I imagine such a thing is very hard to measure.
An epidemiologist said that there is correlation between the viral load and the severity of the resulting illness in studies on mice. He also said something that surprised me, namely that the mechanism involved is unknown. It seems fairly obvious that it has to do with the exponential growth of the pathogen inside the body.
If you need to go out, when you come back, remove all clothes and wash and then have a shower.
[Mumbles something about hormesis.]
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.
The Vmin to be detected by your immune system is small. You want the most time between Vdetected and Vdanger.
For influenza, each infected cell apparently infects ~22 other cells:
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.
Some guy vomited in a restaurant. Then you can clearly model the time from exposure to symptoms in everyone else based on how far away they were when the guy vomited. Though in this case the viral exposure was very high for everyone in the restaurant.
The basic theory is that if you catch the virus, you want to have it in your nose first so your body has time to start a response before it reaches your lungs.
If you get a large dose into your lungs at the start (perhaps because you work at a hospital with insufficient PPE) it's less likely to be mild.
That's a thought that has crossed my mind before: if it's better the farther up in the respiratory system the initial infection happens, then all that hand washing might be a bad idea, at least for the personal outcome. It depends a lot on wether you expect the full wave to eventually roll through until herd immunity or if you expect it to be stopped early, either by continued distancing until it's starved our by a vaccine.
Huh? How does that figure? Hand washing will means less (or no) virii in your nose/mouth.
So, isn't it (a) good in itself, and (b) totally orthogonal to the infection happening "farther up in the respiratory system" (aside the positive, that if it happens and is further up, it will also be less viral content)
If you make "first contact" by inhaling tiny droplets it's possible that they will make landfall right down in the lungs, whereas an infection from dirty fingers is guaranteed to start in the nose/mouth area and will already be an immune system project while it works it's way deeper down. Still worse than not getting infected at all, but if you assume that it will eventually hit you anyways, easing into the infection via the nose would surely be preferable to starting in the lungs where it's actually dangerous.
The reverse of this would be accumulating an infective dose from the leakage amount allowed through by PPE while working in extreme exposure. I doubt that there is empirical data regarding viruses, but everything we've learned about particulate emissions suggests that smaller particles reach deeper into the lungs. So it seems quite convincing to me that people who do fall ill despite PPE fall ill harder. Might explain the prominent medical worker deaths.
Err, you can wash your hands, and it will "disinfect them".
And if the viral content is still in your nose/mouth/neck, you can dissinfect that too to some degree.
So, there's that...
In Bavaria they are only testing people with symptoms and the positive rate is around 10% [1].
Everybody thinks they have it but the symptoms could also be down to a cold. I am not pointing this statistic out to prove you wrong -- I just find it interesting.
[1] https://www.lgl.bayern.de/gesundheit/infektionsschutz/infekt... and search on the page for 'Laboruntersuchungen'. The left axis is number of tests and the right axis is percentage of positive tests.
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.
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.
https://www.medrxiv.org/content/10.1101/2020.03.30.20047365v...
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-...
"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...
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.