Tonight on PBS News Weekend, turmoil at the CDC after the director is abruptly fired

as health secretary Robert F. Kennedy, Jr. eyes sweeping vaccine policy changes.

Then how AI chat bots may be triggering distorted thoughts in users and harming their mental health.

And nearly a year after Hurricane Helene, we meet volunteers from around the world still at work restoring the famed Appalachian Trail.

The overriding thing I think they leave with is the feeling that they're part of something that's bigger than them.

And they know they're connected to other people who care about the same things.

And that might be the highest value.

Good evening. I'm John Yang. On this Labor Day weekend, there's been no holiday from the turmoil and controversy at the agency in charge of protecting the American public's health.

Several CDC leaders have resigned after the White House ousted the agency's new director, Dr. Susan Menares, after less than a month in the position. Her lawyers say it's because she

refused to rubber-stamp unscientific directives and fire dedicated health experts. In just six months,

the agency has lost nearly half its budget,

thousands of employees, and is caught in a political struggle as Health Secretary Robert F. Kennedy,

Jr. moves to reshape the nation's vaccine policies. In an essay in the New York Times this

weekend, Democratic Senator Bernie Sanders of Vermont called for Kennedy's resignation.

Ali Rogan sat down with Dr. Richard Besser, who was acting CDC director in the Obama administration.

He's now CEO of the Robert Wood Johnson Foundation, which we should note is a funder of PBS News.

Dr. Richard Besser, thank you so much for joining us. You've been in

communication with Dr. Menares. What is your understanding of what Secretary Kennedy asked

her to do that was really a red line for her? Yeah, you know, it was really coincidental.

She and I had a meeting scheduled for Wednesday. I reach out to all

directors of the CDC to offer my support. And she thanked me and said that she didn't expect to be in

the position long, that she had two lines that she would not cross when she took the job. One was

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