In the six months since Robert F. Kennedy Jr. took office as the health secretary, the Centers for Disease Control and Prevention has withered, losing thousands of employees, about half of its budget and contracts, and much of its authority over the nation’s vaccine policies.

This week, as Mr. Kennedy ousted the agency’s new director and precipitated the resignation of four other leaders, experts in public health began asking questions unthinkable just a few months ago: Is the C.D.C. dying? And if so, what does that mean for Americans?

In interviews, a dozen public health experts, along with seven former high-ranking officials, described the C.D.C. as badly wounded and fast losing its legitimacy. It can still be salvaged, they said, but only if Mr. Kennedy listens to scientists and restores some of its crucial functions.

“It’s got, like, a heart rhythm that’s not viable at the moment,” said Dr. Demetre Daskalakis, who led the C.D.C.’s center for respiratory diseases until he resigned this week. “If it’s not shocked out of it now, it may not survive.”

Some experts acknowledged that the C.D.C. has its faults and needs serious reform. Its reputation was badly damaged during the pandemic, in part by its own missteps and in part because of misinformation spread by detractors.

But Mr. Kennedy “has not been reforming the C.D.C.,” said Dr. Ashish Jha, who served as the Covid czar during the Biden administration.