The World Health Organization’s emergencies chief said it’s possible the new coronavirus may be here to stay, warning it’s impossible to predict when the pandemic might be controlled.

“This virus may never go away,” said Dr. Michael Ryan, in a news briefing on Wednesday. He said that the number of people infected by COVID-19 so far is relatively low.

Without a vaccine, he said it could take years for the population to build up sufficient levels of immunity to it. “I think it’s important to put this on the table,” he said.

“This virus may become just another endemic virus in our communities,” he said, noting that other previously novel diseases such as HIV have never disappeared, but that effective treatments have been developed to allow people to live with the disease.

Ryan said there remains hope that an effective vaccine will be developed, but even then, it would require a huge amount of work to produce the shots and distribute them worldwide to people willing to be immunized.

“Every single one of those steps is fraught with challenges,” he said.

Maria Van Kerkhove, WHO’s technical lead for COVID-19, added that she recognized some people were “in a state of feeling quite some despair,” but pointed out that stopping the virus even without medical interventions was possible.

“The trajectory of this outbreak is in our hands,” she said. “We have seen some countries bring the virus under control.”