Viktor Mikhailovich Zhdanov (b. 13 February 1914 – d. 1987) was a Ukrainian virologist and epidemiologist who led the fight to eradicate smallpox.
Zhdanov started his career as an army doctor in the Soviet military, and gradually worked his way up in the world of academic medicine until he was the Deputy Minister of Health for the Soviet Union. He had some success treating smallpox outbreaks in the USSR, despite the difficulty of providing vaccines in remote locations. During the Eleventh World Health Assembly (1958) in Minneapolis he presented his success to the WHO, along with a rather startling idea: working together, we might well be able to eliminate smallpox. He was passionate, well-informed, and convincing, and the next year a resolution to this effect was passed.
And it worked. While there were many important movers in the fight against smallpox, including the more famous (in America, anyway) D.A. Henderson -- who took control of the WHO's Global Smallpox Eradication campaign and invented the effective ring vaccination method of treating outbreaks -- Zhdanov was clearly the first mover, the one who conceived and sold the idea to the world.
The last case of smallpox was eliminated in 1978; the last four decades have not seen one death from smallpox, meaning that Zhdanov's project has saved something on the order of 120 million lives.
Zhdanov has received less recognition than he deserves, in part because he was not on the front-lines of the project during the implementation stage, as he moved on to research targeting influenza, hepatitis, and HIV. He is, however, recognized in epidemiological circles as one of the more influential people of the millennium.