We know how the COVID-19 pandemic began: Bats near Wuhan, China, hold a mix of coronavirus strains, and sometime last fall one of the strains, opportunistic enough to cross species lines, left its host or hosts and ended up in a person. Then it was on the loose. What no one knows yet is how the pandemic will end. This coronavirus is unprecedented in the combination of its easy transmissibility, a range of symptoms going from none at all to deadly, and the extent that it has disrupted the world. A highly susceptible population led to near exponential growth in...