[Goose]

I read a lot more than I post here, but the disappointment over inadequate contact test and tracing has me a little puzzled. I was very impressed with the statistics on the number of mild and symptomatic cases, i.e., carriers who don't even know they have the disease.

Doesn't this phenomenon make any attempt to identify whole chains of infected somewhat problematic? Are containment efforts based on contact tracing doomed to failure for that reason? Intuitively, it would seem so.

Not at all. In fact, those cases will ONLY be found by contact tracing. Mildly ill persons don't normally get tested. However, some of the people infected by the mildly ill persons will get ill enough to be tested. The person who is ill will name the mildly ill person as a "close contact". That will cause two things to happen. First, the mildly sick person will be quarantined, period. They will not infect anybody else. Big win. Second, that mildly ill person will be tested and return a positive result. The "close contacts" of the mildly ill person will then be quarantined, preventing any spread from those people who are not yet sick. It is important to realize that we do have one thing going in our favor with this virus. We have a test. If you are contagious, you will test positive with high probability. That allows the second part of the operation above to work. Without a test, it is probably impossible to justify quarantine of "close contacts once removed". Tracking and tracing would still work, just not quite as well.

[Goose]

I read a lot more than I post here, but the disappointment over inadequate contact test and tracing has me a little puzzled. I was very impressed with the statistics on the number of mild and symptomatic cases, i.e., carriers who don't even know they have the disease.

Doesn't this phenomenon make any attempt to identify whole chains of infected somewhat problematic? Are containment efforts based on contact tracing doomed to failure for that reason? Intuitively, it would seem so.

Not at all. In fact, those cases will ONLY be found by contact tracing. Mildly ill persons don't normally get tested. However, some of the people infected by the mildly ill persons will get ill enough to be tested. The person who is ill will name the mildly ill person as a "close contact". That will cause two things to happen. First, the mildly sick person will be quarantined, period. They will not infect anybody else. Big win. Second, that mildly ill person will be tested and return a positive result. The "close contacts" of the mildly ill person will then be quarantined, preventing any spread from those people who are not yet sick. It is important to realize that we do have one thing going in our favor with this virus. We have a test. If you are contagious, you will test positive with high probability. That allows the second part of the operation above to work. Without a test, it is probably impossible to justify quarantine of "close contacts once removed". Tracking and tracing would still work, just not quite as well.