Government officials and business leaders are turning their attention to a looming challenge in the fight against the new coronavirus pandemic: Reopening a $22 trillion U.S. economy that has been shut down like never before.

With some preliminary signs that infections from the virus are slowing, the whole nation is hopeful to get back to business as soon as possible. But a host of questions arise: Under what conditions should people be allowed back to work and stay-at-home orders be lifted? How will people at work be monitored for reinfection or antibodies to prevent a resurgence of the deadly virus? Does it all happen at once or is it staggered? Who is in charge of the effort?

A sharp reduction in new infections is a critical first step, but health experts say other steps will be needed to prevent another devastating outbreak that shuts the economy down all over again. That includes building testing and surveillance systems—and a readiness to reintroduce some social distancing and other mitigations on smaller scale if necessary—to give businesses and individuals confidence that they can return to work without risking infection.

“It isn’t like a light switch on and off,” said Anthony Fauci, a member of President Trump’s task force on the pandemic, in an interview with “The Journal,” a Wall Street Journal podcast. “It’s a gradual pulling back on certain of the restrictions to try and get society a bit back to normal.”

Dr. Fauci said a first condition is a steep drop in the number of cases. “You’ve got to make sure you are absolutely going in the right direction.” Then, he said, “you gradually come back. You don’t jump into it with both feet.”