The firing of the director of the U.S. Centers for Disease Control and Prevention and the resignation of several high-profile agency leaders pose immediate challenges to the operations of the nation’s premiere public health agency, experts said.

It could take “several months” to identify and confirm a replacement for CDC Director Susan Monarez, who was terminated Wednesday after less than a month on the job, said Dr. Georges Benjamin, director of the American Public Health Association. And it could take more time to fill at least four key vacated positions that oversee disease outbreaks, vaccines and public health data.

“The whole chain of command has just been disrupted,” Benjamin told The Associated Press. “It’s like getting rid of your generals in the middle of a war.”

Health experts said Americans could see immediate effects, from confusion over the availability of COVID-19 vaccines to delayed responses to outbreaks of infectious diseases such as measles or foodborne illnesses caused by germs such as E. coli or listeria.

“The average American should worry about their safety and their health and whether information coming out of Health and Human Services is reliable or trustworthy,” said Dr. Anne Schuchat, former principal deputy director of the CDC, who left the agency in 2021.