Epidemiologist who led the battle to wipe out smallpox

One of the world’s most lethal diseases, it ravaged human populations for millennia, and killed an estimated 300 million people in the 20th century alone. Yet now, smallpox is largely forgotten – and for that, much of the credit must go to the American epidemiologist Donald A. Henderson, said The New York Times. In 1966, aged 38, he was appointed to lead a World Health Organisation campaign to wipe out the virus. At the time, it seemed a hopeless task: indeed, Henderson used to say that he was only given the job so that when the programme failed, the US – which had pushed for it – could be blamed. If so, the WHO chose the wrong man, said The Economist. Brawny and brimming with zeal, Henderson was not “inclined to fail”.

The first smallpox vaccine was developed in 1796, and by the 20th century the disease was largely under control in most of Europe and much of the Americas. But attempts to wipe it out in Africa and Asia had all failed. Henderson – D.A. to his friends – realised that mass vaccination was futile. Instead, he followed the strategy, devised by Dr William Foege, of “surveillance containment”. That meant pinpointing every case, and vaccinating all contacts. In the years before fax machines, let alone mobiles, managing such a task on a global scale was almost inconceivably complex. With only a small team, Henderson had to recruit some 200,000 field workers in 50 countries, to act as spotters and vaccinators; and to secure the cooperation of dozens of governments. He needed also to ensure his field workers had sufficient stocks of high-quality vaccines. To that end, he set up new labs and, at the height of the Cold War, travelled to Moscow to get the USSR on the case. Meanwhile, he often had to go into the field to help resolve the problems that arose almost constantly. “In Ethiopia, rebels attacked the vaccinators.” In Afghanistan, efforts to reach afflicted areas were hampered by deep snow and a lack of maps. “In Bangladesh, trucks could not cross the bamboo bridges.” And good work was often swiftly undone, by civil wars displacing populations, or nomads wandering across borders.

Yet by 1975, most of Africa and Asia were smallpox-free; and in 1977, the last naturally occurring case was recorded in a Somali cook (he survived). Two years later, Henderson signed the document declaring smallpox eradicated. It was one of the most important public health initiatives of all time, and it had taken just a decade. But Henderson did not feel he had done his job because, to his disgust, the virus lived on – in labs around the world.

Not one to suffer fools, Henderson could be irascible, but he was a thoughtful man, generous with his time, who readily acknowledged that he had been just one player in a global effort that had required the ingenuity and dedication of thousands of people. He also realised that he had, in a sense, been lucky: smallpox’s symptoms are easy to recognise; the disease has no insect vectors; and its vaccine works for years. He cautioned that other diseases would be harder to tackle, and he was right. Though huge advances have been made against polio and malaria, smallpox remains the only human disease ever to have been eradicated.