These numbers unfortunately tell so little. I tried to find out which countries did how much testing. I know they are from now on testing way more people in Germany, want to test even those with any symptoms of a cold (which they absolutely didn't before), but I don't know if that actually happens.
Well, a tendency can probably be deduced, but if the criteria and numbers change constantly and are different in each country anyway, and we are not really told about them, how can we "work" with these numbers?
Unless a country is decreasing the number of tests run per day over time, I think the number of active cases is very informative. It doesn't matter if the testers are missing asymptomatic individuals, because from a population point of view, they're only relevant if they are a source of infection of symptomatics. And a decline of active cases would indicate they aren't. IOW, if active symptomatic individuals are decreasing, so must active asymptomatics.
A continued decline of active cases has to mean that the reproductive number, R0, is less than one, and that eventually the spread of the virus will be stopped.
I just question whether signs of viral RNA in a swab always means active infection. If you cohabit with a person shedding virus and you breath some into your nose and it gets controlled by your localized innate immune response (no adaptive response), is that something that might be detected as a positive? Is there an empirical difference between viral exposure and viral infection? AFAIK, there has been no close-contact testing of people here in the USA to even generate data on that.
Ah, I see what you're getting at. Yes, i mentioned that problem upthread. In theory, you can have a quantity of virus in your body that is not sufficient to trigger the immune system--or as you point out, only triggers an early nonspecific response, but not the response that results in antibodies. That actually seems like a reasonable explanation for some of these studies that find very high proportions of asymptomatics. My understanding is that it takes probably several hundred CoV particles to infect someone. In theory, one could certainly detect fewer than that by PCR, if they were concentrated in some area accessible to the swab.
This is a situation where even some of those questionable Ab tests that might have high numbers of false positives could be useful. If, e.g., you have 50-90% of some population that tests positive for the virus, but only 5-10% are eventually Ab positive, you have a pretty good idea that the virus positive in most cases does not indicate infection. Continued lack of symptoms would further strengthen this conclusion.
Here in Slovakia antibody testing in home cares started today. Authorities want test all 37 000+ workers and about 42 000 clients. If they find positives they will test them and their contacts with PCR test. I am curious about results. It is quite large sample. About 1,5% of population.
The link doesn't actually say antibodies. I assume you maybe have more information that specifies that. I'm not sure why they would test for Abs, though, if they want to follow up with tracing their contacts, since by then it might be too late. I guess they could use antibodies to target people who are more likely to be positive. But many who are positive for antibodies are likely to be negative for the virus, and vice-versa.
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