Sometimes, a disruptor-in-chief is the thing you want. Sometimes, a disruptor-in-chief is the last thing you want.

What will the U.S. government under the leadership of Donald Trump do in response to the coronavirus as the outbreak grows? Nobody knows. Donald Trump will be the last to know. Why would anybody bother telling him? Will the response be effective and competently administered? JFK and LAX are chaos on an ordinary Monday morning, our borders remain porous in spite of all the big talk, and our enforcement of compliance with visas is, in effect, nonexistent. We have cities full of people, many of them children, who haven’t been inoculated against ordinary diseases because they have fruity ideas about vaccines — ideas that have been spread by, among others, Donald Trump. And, of course, we were already running a $1 trillion deficit without a public-health emergency on our hands — because we refuse to prioritize and to say “No” when doing so is politically painful.

That is the kind of leadership we have. This is not uniquely the fault of Donald J. Trump of The Apprentice and Playboy Video Centerfold, who until this recent turnaround was boasting about the performance of the stock markets as a referendum on his leadership. But he is not exactly rising to the present challenge in a persuasive way, either.

And so what we have is uncertainty. That uncertainty has cost businesses and investors about $3.5 trillion in the past couple of weeks.