Correction to the above: I noticed that tests are updated less frequently than cases. Still, this cite says 50,000 tests per day being done in Germany, and new cases are going up by around 5,000 a day, meaning 10% of those tested have got coronavirus. It still doesn’t make sense to me that people who are tested would have less prevalence of the disease than the general population.
That district is not representative, it was the site of one of the first outbreaks in Germany.
Ah, right. I misinterpreted your last paragraph 
Yes, 0.4% seems not unreasonable - I think that’s compatible with the death rate from South Korea where of course they’ve done rather a lot of testing (last I heard was about 0.6% … but that probably doesn’t count all of the truly asymptomatic people)
Thank you for the link and the translation Absolute. These early first numbers do have to be interpreted cautiously, remembering also antibody positivity lags by some variable amount but guessed by many to average about 2 weeks. But real numbers!!!
Apidistra antibody levels are evidence of* having HAD* the infection (or immunization). The swabs are evidence of actively having virus in the nose and/or throat. The two can overlap and in the first weeks more will test positive on the swab for active infection than on the antibody test having shown they are resolved or resolving, but as people resolve more will test positive for antibodies than for being infected.
Make sense?
From there
Supervise a daycare center from home for your entire working and retirement years? Interesting concept.
Another complication in measuring the true asymptomatic rate is that you’re going to have some people who don’t have symptoms from the coronavirus, but who do have them from some completely unrelated source. For instance, I’ve had a dry cough for my entire life, so me having one now doesn’t mean anything. And in a typical winter, plenty of people will have mild respiratory problems just from the low temperatures, the low humidity, or from routine diseases like colds. So yes, when someone say “I don’t have any symptoms”, they might mean “I have only very mild symptoms”, but they can mean “I only have the same very mild symptoms I’d be expected to have without this virus”.
Absolute already answered that point - if nobody is trying to translate prevalence in Heinsberg to prevalence in the rest of Germany, then it actually doesn’t matter what the prevalence in Heinsberg is.
In that case, the important number is the mortality rate of 0.4%. If you combine that with the German death count of about 2600 then you’ld estimate that the total number of Germans who have/have had it is about 650k rather than than the official 113k
Which, on the one hand, is a ton of missed cases, but on the other hand, not incompatible with estimates I’ve previously seen of undercounts between about 5x and 20x.
Still less than 1% of the population, sadly. So not very close to the point where we could reasonably expect the proportion of already exposed people to have much of an effect on the infection rate
From a practical perspective they really can be considered the same: no symptoms that registered as anything of note.
Yeah, “asymptomatic” really means no symptoms significant enough to seek medical care or stop normal activities such that there is no reporting or other evidence of epidemic spread and contagious people shedding virus without any preventative measures.
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Apidistra,
Again, I’d take these very early numbers with great caution, but sure let’s play as if we can believe the bit.
IF the true IFR for an entire population rate is 0.4% and herd immunity for the particular population (considering its age demographics and current social structures) for the particular germ occurs at 40% THEN the deaths per million expected before herd immunity kicks in is 1600 deaths per million. Italy, Spain, and New York are all running in the 300s currently.
Why to take the death numbers with such caution? Ganglet’s population is just barely over 12K. If they’re saying that 14% of them were infected and about 0.4% of those died then the deaths number is 6 or 7. Be very careful extrapolating from small n numbers.
The other way to read it is to simply note that in Germany with a pretty quick control response and lots of testing right away the infection rate seems to have gotten to 15% fairly quickly with 80% of those infected never having realized that they were sick.
I’ve found a link to the actual preliminary study report. Throwing it into Google Translate is enough to get their methods:
Would love to at least see how well the 500 of the sample reflect the age and household demographics of the town.
500 is a fine first sample but not sure what confidence bounds would be reasonable to place on this. I would not take the 0.4% IFR with much confidence based on this sample, personally.
So, 400 of the 600 households took part. I’m wondering if there might have been something special about the 200 that didn’t.
Well, this paper off of the medRxiv preprint server is interesting:
Investigating the Impact of Asymptomatic Carriers on COVID-19 Transmission
Abstract
Coronavirus disease 2019 (COVID-19) is a novel human respiratory disease caused by the SARS-CoV-2 virus. Asymptomatic carriers of the virus display no clinical symptoms but are known to be contagious. Recent evidence reveals that this sub-population, as well as persons with mild, represent a major contributor in the propagation of COVID-19. The asymptomatic sub-population frequently escapes detection by public health surveillance systems. Because of this, the currently accepted estimates of the basic reproduction number (Ro) of the virus are inaccurate. It is unlikely that a pathogen can blanket the planet in three months with an Ro in the vicinity of 3, as reported in the literature. In this manuscript, we present a mathematical model taking into account asymptomatic carriers. Our results indicate that an initial value of the effective reproduction number could range from 5.5 to 25.4, with a point estimate of 15.4, assuming mean parameters. The first three weeks of the model exhibit exponential growth, which is in agreement with average case data collected from thirteen countries with universal health care and robust communicable disease surveillance systems; the average rate of growth in the number of reported cases is 23.3% per day during this period.
The estimates in the paper are in the same range as some initial speculative modeling I did back in early March (based upon the sketchy data that was available in late February and early March in the North America). I was getting an R[SUB]0[/SUB]>4 and possibly much greater than 6, but there wasn’t enough data to really validate those estimates so I felt that all it really showed was that the R[SUB]0[/SUB] was higher than the official prediction from the WHO and CDC (based on the Wuhan data which is increasingly being shown to be non-representative). Anyway, the paper isn’t yet peer reviewed and should be taken as preliminary but it does suggest that the most plausible way the SARS-CoV-2 virus could have spread so rapidly and with so much community transmission is through a large percentage of asymptomatic carriers.
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Its a preliminary study measuring the concentration of viral particles in sewage, but research done by MIT and a biotech company, showed the rate of infection is at least 5 times the diagnosed rate.
Buuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuut, I heard that is the low end of their estimate, and their actual estimate could be 200x higher than the official infection rate. Which sounds way too high.
One of the comments was (and I"m not sure where they got this info)
Which is a pretty wide spread to make it pretty much meaningless. Anywhere from 5-200 times more infected people than the CFR?
Also I’m assuming this is also only infected people, don’t know if they account for people who have recovered from the illness.
Thats interesting. Wouldn’t that make it one of the most contagious diseases we’ve ever seen then?
The disease did go from the first human infected sometime around thanksgiving to much of the world being on lockdown 4 months later.
Hopefully the affordable antibody tests come out soon. Even if the coronavirus turns out to be a lot less fatal than we expected, it showed how caught off guard and playing in the dark we are in a lot of ways.
Indeed. Quite interesting. I do doubt the top end of their estimates for R[sub]0[/sub].
For two reasons. One, as they say:
Secondly, the infectious time for symptomatic carriers takes no account of the point in the disease’s progress where the subject becomes too ill to circulate in the community.
As we know, the actual numbers of detected infections is still a wobbly number, and variable from country to country. So the input values to fit to are a bit suspect as well. Some analysis of sensitivity to the parameters would not have gone astray.
But overall, it is hard not to think there is good evidence that R[sub]0[/sub] could easily be 6 or more.
What is tickling in the back of my mind is the possibility that the progress of the infection is very sensitive to the initial viral load. Various pointers in the numbers, including this, seem to support the notion that the size of the infecting dose is a significant factor in the progress, and prognosis. This could be good news.
Measles has an R[SUB]0[/SUB] that is typically estimated as between 12 and 18. Chickenpox is about 12. Both are truly airborne (not just aerosol) so basically being in the same room is almost a guarantee of exposure.
And with good reason. We won’t really be able to have a solid estimate until we have a grasp on the percentage of asymptomatic carriers and how contagious they are compared to symptomatic carriers who are obviously coughing or sneezing sputnum.
The viral load is pretty clearly a factor, but there may be others including nutritional or metabolic issues (e.g. potassium imbalance, vitamin deficiencies), undiagnosed underlying conditions, or genetic sensitivity. While incidence of mortality increases with age there are some very young, apparently healthy adults who are contracting the disease and progressing rapidly without explanation. There is a lot that virologists do not understand about this virus and the disease it causes, which makes me somewhat skeptical about the hopes of having an effective vaccine in 12-18 months. I hope I’m wrong about that because as an endemic disease this would have the potential of just randomly striking down people with little warning, and the level of herd immunity to prevent outbreaks given its contagiousness is probably very high.
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It is interesting but the real numbers also have to fit with what was found on contact tracing studies in which secondary infections in households ran something like less than 5 to 15% depending on the study and no more than half who were found to be infected we either without or with only minimal symptoms. (For example.)
I can readily believe that the PCR swab could miss a greater number of the asymptomatic or minimally symptomatic cases who might not be shedding as much or for as long. Ten or somewhat more with no to minimally and mostly not noted symptoms to every clearly symptomatic case I could potentially believe (even if it seems a bit high). Much more than that does not seem compatible with any reasonable interpretation of the contact tracing studies.
This newspaper claims the asymptomatic rate in Iceland, where 10% have been tested, is 50 percent. It’s not a journal article, but it is something, I guess.
Another completely NOT scientific bit to add here.
As I have shared I am a general pediatrician, and I have noticed something in my calls these last several days - several of families who have, by their reports, been strictly in lockdown mode for the last three weeks who have kids with mild symptoms and persistent fevers. Maybe some minimal cough, loose stools, sore throat. Nothing of note really but still fevers off on going on six seven days or longer. Not acting too sick, maybe a bit fussy. No one else in household sick in any way and the kids have not been out at all. Some of these parents have not been out at all, having stuff delivered, not even grocery runs. Locally there is really nothing contagious around other than COVID-19. Parents reasonably puzzled as to how their kid got ANYTHING when no one has been anywhere for three weeks and everyone else in the household has been fine this whole time.
No indication to test these kids and every reason to keep them and their families from having to go to an Immediate Care site set up to see those with potential COVID-19 (our office is set up for only those without any symptoms that could potentially be COVID-19 related). So waiting it out mostly.
The story that makes the most sense to me is that a parent was exposed before they bubbled in, became asymptomatically infected in the 5 to 7 day later common period, and the kid then caught it from the asymptomatic parent showing up with mild symptoms at days 5 to 7 and staying with this mild presentation for the week since.
I don’t know these kids have mild COVID-19. But it really doesn’t fit anything else …
Do the families have or have regular contact with domestic animals? I know the current guidance is that felines can contract the virus and some evidence of human-to-canine transmission but with no observed back-transmission, but…
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