A physician, Fenner served in the Australian Army Medical Corps as a malaria specialist in World War II. After the war, he researched viruses, especially the varieties of pox (he coined the term “mousepox” for the strain that infected mice) and myxoma. He realized the myxoma virus was especially lethal to rabbits, and that virus was released in the wild to get Australia’s plague of rabbits under control. (To prove that was safe for humans, Fenner and two colleagues injected each other with the virus.) “I was able to follow the way in which the virus changed to become less virulent, allowing some rabbits to survive,” he said later. “And those that survived were genetically more resistant, which they then passed on to successive generations. You got this interchange, this balance between virus virulence and host resistance. This was evolution before our eyes.”
Fenner’s early interest in pox led to him being recruited for the final push against smallpox, which killed 300-500 million people in the 20th century and was a leading cause of blindness. A world eradication program had been started in the late 1950s, but smallpox proved difficult to stop completely. He first started as a consultant to the eradication effort, and later he chaired the Global Commission for the Certification of Smallpox Eradication, which was finally able to confirm the disease was gone from the wild. The World Health Organization declared smallpox eradicated in 1979 — the first infectious disease to be completely wiped out. “If you want to protect children from the vast number of infectious diseases,” Fenner advised, “vaccination is by far the best way to do it. If on the other hand, you wish to act against overpopulation, don’t vaccinate anyone, including your own children.” Dr. Fenner died November 22, at 95.