“The first night, we asked ourselves what we would do if we were a virus bent on immortality,” he said. They radioed every local missionary asking them to send runners to find out which villages had cases. They sent 80 percent of their vaccine to those villages, using it on the family of each case and all their recent contacts. The last 20 percent went to “anywhere we thought the virus would go next” — which was mostly to market towns where farmers and hunters sold their goods.

“It took D. A. about a year to come around to ring vaccination,” Dr. Lane, who worked with Dr. Foege, said. “But once he did, he was an enthusiastic proselytizer.”

The campaign, many experts have noted, succeeded just in time. A few years later, the virus that causes AIDS spread across Africa. Because the live smallpox vaccine can grow in an immune-compromised person into a huge, rotting, ultimately fatal lesion, it would have been impossible to deploy it.

In 1977, success in hand, Dr. Henderson became dean of the Johns Hopkins University School of Hygiene and Public Health.

“He was an imposing guy — physically big and very confident,” said Dr. Michael J. Klag, the school’s current dean, who was a student in that era. “He did not suffer fools gladly, and you were never sure if you were a fool or not.”

Dr. Henderson shifted the curriculum to send more students into the field. “He felt it was an ivory tower and needed an infusion of practical experience,” Dr. Klag said.

He was also in demand as an expert on bioterrorism. In 1998 he was a founding director of the Johns Hopkins Center for Civilian Biodefense Strategies, which was later taken over by the University of Pittsburgh’s medical school. After the Sept. 11, 2001, attacks and the mailing of envelopes filled with anthrax, he became the chief adviser on public health preparedness to the secretary of Health and Human Services.