U.S. hospitals are setting up circus-like tents for testing, considering canceling some elective surgeries and calling on retired doctors for help as they brace for an onslaught of coronavirus patients.

The head of the American College of Emergency Physicians expects a “tremendous strain” on the U.S. health system. Experts fear that when federal testing snafus are resolved, a flood of patients will hit U.S. emergency rooms.

And they worry doctors will face agonizing decisions over who gets treatment.