David J. Sencer, 86, Dies; Led Disease-Control Agency

His death, at Emory University Hospital, was caused by complications of heart disease, his daughter Susan said.

Dr. Sencer was the longest-serving director of the Centers for Disease Control and Prevention, the federal agency based in Atlanta, holding the post from 1966 to 1977.

Known as a personable, hands-on executive, he oversaw a substantial expansion of the agency as it dealt for the first time with malaria, nutrition, anti-smoking efforts, health education and occupational safety. Its greatest success under him was a program that eradicated smallpox, beginning in central Africa and eventually extending worldwide.

“I never asked him for anything that he didn’t deliver,” said William H. Foege, who led the smallpox eradication project at the C.D.C., as the agency is known, and who succeeded Dr. Sencer as director. “He said you couldn’t protect U.S. citizens from smallpox without getting rid of it in the world, and that was a new approach. People in the field got all the praise, but he was the unsung hero. He just kept providing what we needed.”

Dr. Sencer’s C.D.C. tenure was tainted in 1976 when a swine flu virus attacked more than 200 soldiers at Fort Dix, N.J., causing severe respiratory disease in 13 of them and one death. Fearing a reprise of the flu pandemic of 1918-19, and urged on by President Gerald R. Ford, Dr. Sencer made the decision — critics deemed it rash and wasteful — that all Americans ought to be immunized.

The United States Public Health Service subsequently ordered the production of up to 200 million doses of vaccine, but the epidemic never materialized. Instead, a rare, potentially fatal nervous system disorder that causes paralysis, known as Guillain-Barré syndrome, appeared in rising percentages of the 45 million people who had been vaccinated, causing more than two dozen deaths. Dr. Sencer was vilified by some but defended by at least as many.

“Dave Sencer made a hard choice, and he did it for the right reason — to protect the American public,” said James W. Curran, dean of the Rollins School of Public Health at Emory, who worked at the C.D.C. with Dr. Sencer. “We didn’t always agree. I’m not saying we’d have been better off with a swine flu epidemic. He was trying to protect Americans had there been one, and absent one, there was bound to be criticism.”

The same year, 29 people who attended an American Legion convention in Philadelphia were killed by a mysterious ailment that quickly became known as Legionnaires’ disease. In an atmosphere of mounting public panic, Dr. Sencer, fearing an outbreak of swine flu or another infectious virus, dispatched 20 epidemiologists to the scene, but it took months for the agency scientists to determine the cause, which turned out to be a strain of bacteria found in the hotel air-conditioning system.

In the aftermath of both scares, and after Jimmy Carter succeeded Ford as president, Dr. Sencer was removed from the directorship by Joseph A. Califano Jr., President Carter’s secretary of health, education and welfare, as the Department of Health and Human Services was then known.

Dr. Sencer worked briefly in the private sector, but returned to public service in 1982 as health commissioner of New York City as the AIDS epidemic was taking root in the city. Admired by some for bringing doctors and public health officials together for weekly information exchanges, he was, as the leading health policy representative of Mayor Edward I. Koch’s administration, criticized by others, especially in the gay community, for dragging his feet.

“He and his reign accounted for one of the most disastrous experiences of public health anywhere in the world,” Larry Kramer, the AIDS activist and playwright, said in an interview. (Mr. Kramer’s play about AIDS in New York in the 1980s, “The Normal Heart,” has just opened in a Broadway revival.) “What did he do? He didn’t do anything. He had a mayor who said, ‘I don’t want to know,’ and Sencer fell into line.”

But James Colgrove, a professor at Columbia University’s School of Public Health and the author of the recently published book “Epidemic City: The Politics of Public Health in New York,” gave Dr. Sencer credit for amending the city’s codes so that AIDS cases were treated confidentially, defending the right of children with AIDS to attend public schools, and being an early advocate for a city-sponsored needle-exchange program.

Dr. Sencer was rightfully criticized, Mr. Colgrove said, for not being a better public educator. He failed, for example, to produce and distribute guidelines for sexual risk reduction for gay and bisexual men and did not reassure the public early on that AIDS was not spread by casual contact, Mr. Colgrove said.

“On the other hand, there was a lot of uncertainty at the time about how the virus was transmitted,” Mr. Colgrove added. “And you have to keep in mind he was working in extraordinarily difficult conditions. The health department had been gutted by the city’s fiscal crisis of the 1970s and had lost about a quarter of the staff. He helped strengthen the department, especially in areas like epidemiology and bio-statistics. But once AIDS emerged, it overshadowed everything else.”

David Judson Sencer was born on Nov. 10, 1924, in Grand Rapids, Mich., where his father, who died when David was a boy, was in the furniture business. He was raised by his mother, Helen Furness, and earned scholarships to the Cranbrook School, near Detroit, and Wesleyan University. He left Wesleyan before graduating to join the Navy, which sent him to medical school at the University of Mississippi. He completed his medical degree at the University of Michigan, and later earned a master’s in public health at Harvard.

While at Michigan he spent a year and a half in the hospital with tuberculosis, and his first job with the Public Health Service was screening migrant workers in Idaho for the disease. He joined the C.D.C. as assistant director in 1960.

Dr. Sencer lived in Atlanta. In addition to his daughter Susan, a pediatric oncologist in Minneapolis, he is survived by his wife, Jane Blood Sencer, whom he married in 1951; another daughter, Ann, an oncology nurse practitioner, of Atlanta; a son, Stephen, general counsel for Emory University, and six grandchildren.

While at the C.D.C., Dr. Sencer was instrumental in starting Emory’s program in public health in 1974; by the 1990s it had evolved into the Rollins School.

“Dave Sencer was a public health giant,” said Dr. Thomas Frieden, the current director of the C.D.C. “And until the end he continued to be a thoughtful and vibrant member of the public health community. At the height of the H1N1 pandemic of 2009, he was here full time, and I said, ‘Can I pay you?’ He said, ‘No, this is a labor of love.’?”