The scourge of smallpox is at least as old as the pyramids of ancient Egypt. Some estimates suggest it emerged in humans about 10,000 years ago. This was about the same time that people began to congregate in large numbers in the first cities, created during the shift from small hunter-gatherer communities to larger settlements of agriculturists, which allowed infections to spread more easily. The oldest direct evidence of smallpox comes from the mummified body of Pharaoh Ramses V, who ruled in the 12th Century BC and died with tell-tale lesions on his face.
Smallpox raged for two millennia. It killed an estimated 400,000 Europeans annually at the end of the 18th Century, and was responsible for between 300 and 500 million deaths globally during the 20th Century.
That all ended with a WHO global eradication campaign based on smallpox vaccination. The campaign began in 1967. By 1971, the last case occurred in the Americas, followed in 1975 by the Indian subcontinent. The last natural case of smallpox worldwide was in Somalia in 1977, and in 1980 the WHO General Assembly declared the disease eradicated globally — only the second infectious disease to achieved this status, the other being rinderpest, a disease of cattle, in 2011.
Although the variola virus that causes smallpox no longer exists in the wild, two laboratories — one in the US and one in Russia — still hold stocks under a Cold War agreement hammered out over fears of its use in biowarfare. However, anyone can study the virus’s full genome, which was published in the open scientific literature in the 1990s, and there is at least one account of journalists trying to synthesise parts of the virus by mail order to show just how easy it might be for bioterrorists to make the entire virus from scratch.
Such a bioweapon could prove deadly especially as most young people in the world now have never been vaccinated against the virus and could be especially vulnerable to its re-appearance in a weaponised form.