If it takes 10 days for antibodies to be detected, the testing only measures the level of infections on ~April 1. The level of infections now -- 20 days later -- could be easily be double or triple what they were then.
True, likely a fair number of false negatives.
If we assume this takes 10 days or more, actual infection levels could be double, triple or more the measured level, depending on the growth rate of infections during that time lag.
Hopefully new infection growth has slowed substantially, but yes, infection levels will certainly be higher.
This is one of many reasons some antibody studies could be substantially understating the level of infections.
Yikes!
Could absolutely be. But remember, we don't actually know what the antibody tests are telling us, except that with high likelihood the prevalence in the places tested is less than 5%. It could be 0.5%. It could be 1.5%, it could be 3%. No one knows.
To think of it simply, the antibody tests used so far can't
accurately measure prevalence below about 5%. We need to get calibration data on the tests for the numbers to be useful. Once we get a test that has high specificity (actually measures at 99.5% specificity (or whatever)
for a very large number of test samples, so also has high confidence), then we can bound these numbers a bit better. Remember that for very low prevalence, you have to have extremely high confidence in the exact specificity of your test. (Realistically it's probably easier to just test a higher prevalence population, or use a different test!)
For now, all we can say is that some unknown number below about 5% have been infected, and the real number of infected people could be either higher or lower than that unknown %. So the actual prevalence is N*M%, where N is unknown and greater than 1, and M is unknown and between 0 and 5 (or whatever).
As the threads you referenced say, it's all an academic debate until we have better certainty on those numbers - we simply have to stop the virus, since it collapses healthcare systems when left to its own devices.
Once we have nice and certain numbers, and learn more about the virus spread, then we can adopt more targeted measures if there are some which will work.
Just how many people do you think are infected in NYC? What would you guess the prevalence will end up being there? I am guessing between 20 and 30%.
In LA County, I would guess SARS-CoV-2 antibody prevalence is between 1 and 2%, as of today (would have been quite a bit lower a couple weeks ago).
