The Demon in the Freezer by Richard Preston is chilling reading during this age of bioweapons and fear over weapons of mass destruction. Published in 2002 after the anthrax scare (which is also covered along with smallpox) this is one frightening book precisely because it is nonfiction. D. A. Henderson, one of the people who fought for eradication of smallpox, said: "Smallpox was the only disease we know of for which there were deities. It was the worst human disease. I don't know of anything else that comes close." The smallpox virus aptly fits the WMD description. Although officially declared eradicated in 1978, there are stockpiles of the smallpox virus held in the USA and the Soviet Union. There may also be other countries who have secretly stockpiled some smallpox virus, perhaps as weapons.
It is known that the Soviet Union was making weapons grade small pox virus. One run of the Soviet Vector research group's 300 gallon tank would produce "enough smallpox to give each person on the planet around two thousand infected doses of small pox." Smallpox is highly contagious and spreads exponentially. "It has taken the world twenty years to reach roughly fifty million cases of AIDS. Variola [smallpox] could reach that point in ten or twenty weeks." "It is generally believed to be the most dangerous virus to the human species." "Smallpox can bring the world to its knees."
Perhaps one of the most frightening facts is that "Today almost everyone who was vaccinated against smallpox in childhood has lost much or all of their immunity to it."