On December 9, 1979, the Global Commission for the Certification of Smallpox Eradication signed their names to the statement that "smallpox has been eradicated from the world."
It was the first time that a disease had been banished from the earth by the planning and action of the world's public health professionals. And it became a model for later (ongoing) efforts to eradicate polio and several lesser known diseases.
The disease only spread from human to human, so there had been an unbroken chain of infection for more than three millennia. In the 1960s, before the eradication program, more than half a million people died every year from the disease.
But in country after country, vaccination and isolation programs lowered rates of infection until the numbers dwindled to one person who was infected, the last patient.
In Botswana in 1974, it was a little girl, Prisca Elias. In Pakistan, 1976, Kausar Parveen. Rahima Banu, Bangladesh, 1976. Amina Salat, Ethiopia, 1976.
Finally, someone had to be the last person on Earth to contract smallpox, and that person was Somalia's Ali Maow Maalin.
Ali Maow Maalin was exposed to the disease on October 12, 1977, while guiding a vehicle with two smallpox-infected children. On the 22nd, he fell ill and developed a fever. By the 26th, the rash appeared on his skin. He was misdiagnosed with chickenpox and sent home.
As his symptoms developed, it became clear he had smallpox, but Ali Maow Maalin did not want to go to an isolation camp, so he did not tell local disease surveillance officials. A friend, however, eventually reported his condition and collected a reward.
All told, he came into face-to-face contact with 91 people, which led the World Health Organization to undertake a massive intervention to prevent the re-spreading of the disease.
An intensive search began to find everyone with whom he had come into contact. In all, 91 face-to-face contacts were identified, 12 of whom had no vaccination scar, and six who had been hospital patients or visitors. Heroic measures were taken, including a search and vaccination of the town and of everyone entering or leaving town at any one of four checkpoints. House-by-house searches throughout the region were conducted monthly, and a national search was completed on December 29.
But no one caught the virus.
So, on October 16. 1979, after nearly two years of monitoring, the WHO declared Smallpox Zero.
And Ali Maow Maalin went into the history books as the last man on earth to catch wild smallpox. He died this year of malaria, after years of working to eradicate polio.
Now, the only potential sources of infection are the labs that do research on the virus. In 1978, a British woman caught the disease from one of these stockpiles. She died. The researcher who ran the laboratory committed suicide.
Some researchers have been pushing for the destruction of laboratory stocks since the 1990s, but US and Russian bioterror researchers have fought the proposal, saying they need more time to develop defensive measures.
In 2011, the final decision on the deadline for the destruction of the virus was pushed back another three years.