There are likely over 1 million people infected with COVID-19 in the US right now. I doubt any contact tracing is going to be useful at this point, and isolation has slowed the spread but it’s reduced it enough that contact tracing is likely viable.
I think you'll learn something from 3brown1blue's youtube video on simulating different intervention techniques. It's from a few weeks ago, but it very clearly shows how valuable contact tracing is, during any stage of the outbreak.
3brown1blue’s video is a very simplistic introduction to the subject. It’s illustrative not predictive.
Contact tracing is clearly useful, but on it’s one does not change the basic reproduction numbers much. Look at South Korea which still has active infections despite active contact tracing and very successful social distancing.
Contact tracing COVID-19 is suplimental not a solution.
PS: As to my point, if you’re a grocery store employee in NYC you are likely to have been in contact with someone with COVID-19 in the last week. We can’t simply send all of them home, that’s the issue with contact tracing when a meaningful percentage of the population is infected. You need looser restrictions which reduces effectiveness.
I care about America, but I live in NZ where the situation is much better (so far) and effective contract tracing is undoubtedly going to be very important.
“but not reduced it enough that contact tracing is likely viable”
For example, NYC has seemingly slowed the spread enough it’s possible to Test for and track new cases. But if you dig into their numbers 4,264 deaths are linked to COVID but where not tested prior to death. https://www1.nyc.gov/site/doh/covid/covid-19-data.page. They have little idea who’s currently infected and “ Due to delays in reporting, recent data are incomplete.”
Essentially they need a solid 2 weeks of minimal new cases. At which point they can start meaningful contract tracing, but contract tracing does not mean you can just get back to normal. Just slightly reduce the amount of isolation.
My understanding is that these tools are mostly being developed to allow reopening of things once the first wave dies down, with infrastructure in place to support contact tracing and reduce the impact of any second wave.
Reopen a small percentage of things, yes but not go back to normal. It provides minimal gain which is import only when the case reproduction rate is close to 1.
Remember, virus still doubles every 2-3 days under normal conditions. Without a vaccine or herd immunity, contact tracing alone does very little. It’s enough to reopen dental offices possibly hair salons, not schools.
