That's a really good point! If we can reduce R_t with widespread social distancing, wearing masks, washing hands etc. down to <= 2 we are in much better place a

That's a really good point! If we can reduce R_t with widespread social distancing, wearing masks, washing hands etc. down to <= 2 we are in much better place and this app could seal the deal and we could just about eradicate the disease. And even if we "only" drive R_t to almost 1 we can at least buy a lot of time for our healthcare workers, which is valuable. Either way, I didn't mean to be that pessimistic. I think an ensemble approach is necessary. For now, general (easy to follow) shelter in place rules, followed by test and trace using these apps, and then targeted relaxation of the rules as we discover what we can reopen without causing a spike in R_t.