I think that approach is exactly why contact tracing didn't work. A virus that spreads as contagiously and stealthily as this one means that contract tracing al

I think that approach is exactly why contact tracing didn't work. A virus that spreads as contagiously and stealthily as this one means that contract tracing alone is not able to achieve Re<1. Eventually (in the case of Washington state, apparently with the first known case?) someone escapes your net and then exponential growth does its magic, because you aren't decreasing Re for anyone not already in your contact graph. (CDC refused to test anyone without a clearly documented link to Wuhan) A working version of this that actually affects the asymptotics rather than just buying you a few weeks at best has to be able to identify new case clusters while they are small, and then find and isolate a significant fraction of the cases (working backward as well as forward). Table stakes for this is the ability to test everyone with flulike symptoms who tests negative for flu (and flu tests have horrible sensitivity, so that is a lot of people). As I see it from my comfortable armchair, CDC should have made sure long before the epidemic that the RT-PCR capacity to do that existed (doing other work at private and public labs) and could be recruited and online to do this within a few days of the virus being sequenced. You also would need everyone to at least moderately change their behavior because I don't think this would be enough by itself. Simple things like not going to work sick or tolerating co-workers or employees who do seem like feasible changes with both cultural and legal levers to pull that could be very low cost and contribute significantly to Re reduction. More speculatively, you might be able to do even better using pooled PCR tests to look for RNA in large groups, giving you a chance to spot even asymptomatic cases. Is there viral rna in sewer water or garbage? PCR amplifies exponentially, it should be able to cope with a fair amount of dilution.