Smallpox is the only human disease that human beings have ever deliberately driven to extinction. For at least three thousand years it was among the great killers of our species, a scourge that scarred the mummified face of Pharaoh Ramesses V and swept through the palaces of emperors as readily as the huts of the poor. It killed perhaps a third of those it infected, blinded and disfigured many who survived, and in the centuries after Europeans carried it to the Americas it helped depopulate whole civilisations. In the twentieth century alone it is estimated to have killed hundreds of millions of people.
The first crack in its armour came not from a laboratory but from a piece of country folklore. In the dairy districts of England it was said that milkmaids, famous for their clear complexions, did not catch smallpox — because they caught cowpox, a mild disease of cattle, from the udders they handled. In 1796 a Gloucestershire doctor named Edward Jenner decided to test the story. He took matter from a cowpox sore on the hand of a milkmaid named Sarah Nelmes and scratched it into the arm of an eight-year-old boy, James Phipps. The boy suffered only a mild reaction. Weeks later Jenner deliberately exposed him to smallpox itself, and the boy did not fall ill. Jenner called his method vaccination, from vacca, the Latin for cow.
From a country cure to a global campaign
Vaccination spread across the world through the nineteenth century, cutting smallpox back sharply in wealthier nations. But the disease still raged across much of Asia, Africa and South America, and eliminating it everywhere seemed a fantasy. In 1959 the World Health Assembly resolved to try; progress was slow and underfunded until, in 1967, the World Health Organization launched an Intensified Eradication Programme. That year smallpox still infected an estimated ten to fifteen million people across more than thirty countries.
The campaign's genius was a strategy called surveillance and containment, better known as ring vaccination. Rather than trying to vaccinate every last person on a crowded continent — an impossible task — teams hunted down each new outbreak, then vaccinated everyone in a ring around the infected: their family, neighbours and contacts. Smallpox spreads relatively slowly and only between people, with no animal reservoir to hide in, so if you could throw an immune barrier around every spark, the fire would burn itself out. Health workers travelled by jeep, boat and camel, carrying photographs of pockmarked children to help villagers recognise cases and offering rewards for reporting them. The tool they carried was almost as clever as the strategy: a cheap two-pronged bifurcated needle that held a precise droplet of vaccine in the gap between its tines and could be reused after sterilising, letting a barely trained worker vaccinate dozens of people an hour in the remotest village.
The last cases
Country by country the map went clear. India, long thought the hardest prize, recorded its last case in 1975. The final naturally occurring case of smallpox was in Somalia in October 1977, in a young hospital cook named Ali Maow Maalin, who had the milder form of the disease, Variola minor — the more dangerous Variola major had already claimed its last natural victim in Bangladesh in 1975. Maalin recovered and later worked on polio eradication in the same country. That should have been the end of it.
There was a tragic coda. In 1978 a medical photographer named Janet Parker, working in a building above a laboratory at the University of Birmingham in England that still handled the virus, became infected and died — the last person on Earth known to die of smallpox. The professor whose laboratory it was took his own life during the investigation. The episode hardened resolve to lock the virus away.
On 8 May 1980, the World Health Assembly formally declared smallpox eradicated — the first and, among human diseases, still the only such victory. The variola virus that caused it now survives, officially, only in two high-security freezers: one at the Centers for Disease Control in Atlanta and one at a state research centre in Russia. Whether even those last stocks should be destroyed has been argued for decades.
The achievement stands almost alone. Of the countless diseases that have plagued humanity, only one other — rinderpest, a cattle plague declared gone in 2011 — has been eradicated at all, and that one afflicts animals. Polio and Guinea worm have been pushed to the brink but not yet over it. Smallpox remains the proof that it can be done: that a disease older than the pyramids could be cornered, outmanoeuvred and erased, and that the whole thing began with a doctor who took a country rumour about milkmaids seriously.
Quiz nuggets
- Edward Jenner performed his famous vaccination in 1796, using cowpox from milkmaid Sarah Nelmes to protect the boy James Phipps.
- The word "vaccine" derives from vacca, Latin for cow.
- The WHO's Intensified Eradication Programme began in 1967 and relied on "ring vaccination" (surveillance and containment).
- The last natural endemic case was Ali Maow Maalin in Somalia in 1977; Janet Parker died in a 1978 UK laboratory accident.
- Smallpox was declared eradicated on 8 May 1980 — the only human disease ever eliminated.