Epidemiologists and infectious disease experts interviewed before the Wednesday briefing doubted that the virus would go away, and did not rule out the prospect of a worse crisis in the fall if the two diseases strike at the same time.

“When flu season comes, there is the possibility that we will be dealing with two respiratory viruses at the same time — flu and Covid,” Dr. Thomas Frieden, the former head of the C.D.C. and the president of Resolve to Save Lives, a nonprofit focused on disease prevention, said in an email. “This could be a double challenge for our health care systems.”

Even if social distancing and other mitigation measures succeed in “flattening the curve,” once those strictures are loosened, cases could surge again, Dr. Frieden said.