‘The coronavirus panic is dumb.” I hesitate to disagree with Elon Musk, but here goes.

The wrong way to think about the rapid spread around the world of the novel coronavirus, 2019-nCoV, and the disease it causes, Covid-19, is to say—as another smart and wealthy man put it to me last Monday—“Remember the H1N1-A virus of 2009? Neither do I. It infected a significant chunk of the globe, killed 20,000 U.S. citizens and we got over it pretty quickly.” He might have added that 20,000 is less than half the number of Americans who...