The ability of the American health care system to absorb a shock — what experts call surge capacity — is much weaker than many believe.

As a medical doctor who analyzes health issues for The Upshot, I strive to place your fears in context and usually tell you that you shouldn’t be nearly as afraid as you are. But when it comes to the nation’s response to the new coronavirus, I cannot be so reassuring.

A crucial thing to understand about the coronavirus threat — and it’s playing out grimly in Italy — is the difference between the total number of people who might get sick and the number who might get sick at the same time. Our country has only 2.8 hospital beds per 1,000 people. That’s fewer than in Italy (3.2), China (4.3) and South Korea (12.3), all of which have had struggles. More important, there are only so many intensive care beds and ventilators.

It’s estimated that we have about 45,000 intensive care unit beds in the United States. In a moderate outbreak, about 200,000 Americans would need one.