The novel coronavirus spreading around the globe “may never go away,” becoming a long-term fact of life that must be managed, not an enemy that can be permanently eradicated, a top World Health Organization official said on Wednesday.

“This virus may become just another endemic virus in our communities, and this virus may never go away,” Mike Ryan, head of the organization’s health emergencies program, said at a news briefing. “H.I.V. has not gone away but we’ve come to terms with the virus and we have found the therapies and we have found the prevention methods, and people don’t feel as scared as they did before.”

“There are no promises in this and there are no dates,” he said, tamping down expectations that the invention of a vaccine for the coronavirus will provide a quick and complete end to what has become a global health and economic calamity. A good vaccine might be developed, but there is no telling when, he added, calling it “a moon shot.”

If infected people become immune or resistant, then when enough people have had the virus, there will be fewer left who can catch it or spread it, making outbreaks more manageable. But no one knows how long that will take.

“The current number of people in our population who’ve been infected is actually relatively low,” Dr. Ryan said.

He also expressed cynicism about the prospects for eradication even with a vaccine, saying, “we have some perfectly effective vaccines on this planet that we have not used effectively for diseases we could have eradicated.” He cited the recent outbreaks of measles around the world.

The only human disease that has been eradicated is smallpox.