A
disease caused by
variola virus, characterized by a
rash of pus-filled skin
lesions covering the body but most prominent on the
face,
arms, and
legs. Smallpox is
fatal in about 30 per cent of cases.
Smallpox is highly communicable, transmitted by infected saliva droplets that are transferred in normal face-to-face contact.
Smallpox's incubation period is about 12 days, and comes on like a the flu: initial symptoms include fever, fatigue, and head- and backache. The rash comes two to three days later. After a week, the skin lesions fill with pus, then they scab over, and they ordinarily separate and fall off in three to four weeks. Often, they leave extensive and easily recognizable scarring.
There is no treatment for smallpox, besides symptomatic relief (replacing lost fluids, medicine to control the fever, and so on). Still, vastly improved sanitary conditions in hospitals make the odds of recovery much better than they used to be; in some communities, smallpox was 90-per-cent fatal.
Vaccination
There is a modern smallpox vaccine, based on the vaccinia virus (from which the word "vaccine" is derived). Vaccinia is a genetic relative of variola, but nowhere near as virulent; fighting through a vaccinia infection provides near-immunity to smallpox. Smallpox vaccination is out of fashion these days because smallpox is not thought to exist in the wild (more on this shortly); vaccinia is fatal in about one person in a thousand, and with the risk of smallpox infection so low, authorities haven't considered it worth the risk. Canada and the U.S. stopped mass vaccinations in 1973; some countries, especially in Africa and Asia, still require it for travellers.
History and eradication
The disease is at least 3,000 years old, with cases confirmed in China, India, and North Africa. Smallpox thrives in dense populations, and became extremely common in Europe in the 17th and 18th century. In the "New World," smallpox was used as a crude bioweapon against native populations; Cortez took the Aztec empire after (probably accidentally) contaminating the natives in Mexico, and settlers in North America deliberately traded smallpox-infected blankets to native populations to weaken them.
In 1967, the World Health Organization (WHO), a United Nations agency, started a mass vaccination campaign; smallpox was killing as many as 15 million people a year. As such diseases go, smallpox is a relatively easy target: there's only one strain, animals don't carry it, and everyone who gets the disease shows symptoms.
The WHO's program was fantastically expensive, but it had the rare Cold-War-era support of both the U.S. and the Soviet Union, plus China and India and the powers of Europe. The WHO was willing to pay for doctors' medical educations if they'd agree to do tours of duty racing around the world, plunging into jungles and climbing mountainsides, immunizing virtually anyone they could find. In some cases, the doctors and nurses with makeshift tents and needle kits were the first representatives of modernity native groups ever encountered. Even so, once the teams explained what they were there to do (not always easy), the people they were there to jab were often remarkably receptive: everyone had seen what smallpox could do.
The last recorded natural case of smallpox was in Somalia in 1977. The WHO declared the disease eradicated in 1980.
The smallpox campaign, incidentally, demonstrated how difficult it is to try to wipe out any disease. Smallpox was easy, relatively speaking, but it still took unprecedented international co-operation, millions of dollars/rubles/pounds/yuan, and 10 years.
Current status
Smallpox is known to exist in cultures in two countries: at the Centers for Disease Control in the United States, and in state biological labs in Russia. There are also probably "weaponized" forms of the virus in states with biological warfare programs. The WHO recommended that the last laboratory cultures be destroyed in 1999, but neither the U.S. nor Russia has complied; they both make the case that if there ever were another outbreak, it would be useful to have samples ready to go.
As a weapon, smallpox is of mixed value: it can cause large numbers of casualties, theoretically, but the long incubation time makes it a strategic, rather than a tactical weapon. Spreading it would be difficult: as soon as the first victims became visibly sick, known isolation and vaccination plans would slam into action. (Soldiers are regularly vaccinated, so smallpox would be of negligible use in a military setting.)
Every so often, the virus "gets loose" in a lab, and there's a localized epidemic. One such incident in the U.S. resulted in the suicides of two scientists who feared their mistakes would be responsible for undoing the success of the eradication campaign.