[linuxhansl]

> But if the virus has already spread to 30, 40, heck 50 percent of the population

_If_ is the key part of this sentence. We simply do not know, which is why - as you point out - testing is key!

If we were strict on lock-down and on testing, we can be very effective with this:

After a few (say 6 or 8) weeks if lock-down we can know with high likelihood who is and who is not sick. Now test all the sick people (and their friends), and start testing the general public for anti-bodies. Then start tracing any new infections.

That requires folks following the lock-down and health measures and the mass availability of virus and anti-body tests.