A month ago, on August 8th, Dan Jernigan, a bespectacled sixty-one-year-old scientist, was the lone senior leader on the campus of the Centers for Disease Control, in Atlanta. He sat at his desk in a five-story glass-and-concrete building that contains the National Center for Emerging and Zoonotic Infectious Diseases, the largest of the C.D.C.’s dozen centers. Jernigan was its director. He’d been at the agency, in a variety of roles, including ones overseeing vaccine safety and influenza control, for thirty years, under five Presidents. It was five o’clock, on a typical Friday, when he heard what sounded like a jackhammer outside the building. The sound continued for nearly fifteen minutes. “A laboratory-science lead came to my office,” Jernigan told me. “She’s on the phone with her husban

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