D.A. Henderson, right, speaks at the University of Arkansas for Medical Sciences about the risks of bioterrorism.Neemah Aaron / AP

D.A. Henderson, an American public-health official who led the international campaign to eradicate smallpox in one of the greatest scientific endeavors of the 20th century, died on Friday. He was 87 years old.

Henderson’s death was announced Saturday by the University of Pittsburgh Medical Center, where he taught as a public-health professor.

When Henderson, then a 39-year-old epidemiologist, became the first chief of the World Health Organization’s smallpox-eradication unit in 1967, the virus killed an estimated two million people every year on three continents. By the end of his tenure there 10 years later, the disease was all but wiped out worldwide. The WHO certified in 1980 smallpox had been completely eradicated—a first in human history. Its absence spared an estimated 60 million lives that would’ve been lost during the almost four decades since then.

The enemy, which Henderson called “the oldest of scourges and the most devastating,” was an ancient one. Smallpox first appears in the historical record 5,000 years ago and never truly leaves it. The disease infected Abraham Lincoln at the height of the Civil War and disfigured the 7-year-old Georgian boy who would become Joseph Stalin. It killed pharaohs and saints, tsars and peasants, merchants and nobles alike during its periodic waves throughout Africa and Eurasia. Millions of indigenous people died after its arrival in the New World, where it contributed to the depopulation of the Americas. An estimated 500 million people succumbed to the disease in the final century before its eradication. If homo sapiens had a nemesis, it was smallpox.

“No disease has ever been so instantly recognized or so widely known and feared,” Henderson later recalled in his 2009 book on the eradication campaign. “Smallpox was hideous and unforgettable.”

For me, the memory of a ward full of smallpox victims thirty-five years ago in Dhaka, Bangladesh, is still vividly etched in my mind. The ugly, penetrating odor of decaying flesh that hung over the ward; the hands, covered with pustules, reaching out, as people begged for help. Neither water nor food offered comfort; pus-filled lesions covered the insides of their mouths, making it painful for them to even chew or swallow. Flies were everywhere, thickly clustered over eyes half-closed by the pustules. More than half the patients were dying, and there was no drug, no treatment that we could give to help them.

Smallpox had one crucial weakness: only humans can transmit it to one another. Epidemiologists in the mid-20th century began to suggest the virus could be driven to extinction through mass-vaccination campaigns. But the logistical hurdles were immense. In order to succeed, the number of active human smallpox infections would need to be reduced to zero, even in endemic hotspots like Brazil, Ethiopia, and India. Even as Henderson launched the WHO campaign in 1967, more than a few public-health experts dismissed smallpox-eradication as a utopian fantasy.

Donald Ainslie Henderson was born September 7, 1928, in Lakewood, Ohio, a comfortable middle-class Cleveland suburb. After receiving his medical degree in 1954, he joined the U.S. Public Health Service to fulfill a selective-service requirement in the aftermath of the Korean War. From there he transferred to the CDC’s epidemic-intelligence division and soon found himself serving as its chief. Henderson savored the challenges of tracking outbreaks through “shoe-leather epidemiology.”

“Every outbreak was unique—how it had occurred and developed, which groups were infected, what were the best ways to deploy community and federal resources, and what could be done to prevent a recurrence,” he later wrote. “There was nothing routine about the job, and it demanded a great deal of rapid learning.”

In 1967, the WHO General Assembly, pushed first by Soviet officials and then by the U.S. government, approved a global smallpox-eradication campaign. Henderson was tapped to lead the project—a move intended by WHO’s leadership, he later claimed, that would allow them to blame the United States if it floundered.

To achieve eradication, Henderson and his small WHO staff coordinated with hundreds of doctors and thousands of local health workers throughout Africa, Asia, and South America. They conducted surveillance, tracked epidemics, and administered vaccines in a targeted effort to eliminate it country by country. Those efforts often required navigating civil wars and refugee crises, dilapidated public-health systems, and national politics and Cold War rivalries, as well as the WHO’s balkanized bureaucracies—a task at which Henderson excelled.

Henderson left the program in its waning days to serve as dean of the Johns Hopkins School of Public Health, but did not leave the issue of smallpox permanently. The Soviet Union’s collapse in the 1990s revealed the existence of a massive biological-weapons program in violation of international treaties, raising the specter that the disease could return. Henderson, who supported destroying the last smallpox samples at the CDC’s labs in Atlanta, Georgia, and Russia’s Vector Institute in Siberia, also backed the resumption of smallpox-vaccine manufacturing after the Soviet revelations and the September 11 attacks—a grim postscript to the most formidable medical accomplishment of the 20th century he had helped secure.

“When this all began for me in 1961,” he wrote, “I had not the slightest inkling that smallpox would be a disease that would preoccupy me for a lifetime. Whatever the quandaries, I return to the basic fact that, for the first time in history, a disease has been eradicated—the most serious of all the pestilential diseases.”

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