Passengers getting tested

Military personal pass out information to travelers as they arrive at Terminal 4 at JFK International airport in New York City on Dec. 22, 2020. Passengers flying from Britain to New York with British Airways or Delta will have to first test negative for coronavirus, New York Gov. Andrew Cuomo announced on Dec. 21. The airlines agreed to the measures over growing concerns about the fast-spreading variant of COVID-19 that has prompted more than two dozen countries to suspend flights from the U.K.

A new strain of Covid-19, more contagious than previous strains, is now circulating in dozens of countries. Other new strains, such as one first detected in South Africa, will almost certainly emerge.

Aside from the challenges these mutations pose to public health, they will also be a test of our moral and political principles. As exhausted as we all are from making stressful judgments throughout this pandemic, we are about to face some of the most difficult trade-offs yet.

Tyler Cowen is a Bloomberg Opinion columnist. He is a professor of economics at George Mason University and writes for the blog Marginal Revolution. His books include "Big Business: A Love Letter to an American Anti-Hero."