Smallpox is a contagious, disfiguring and often deadly disease caused by the variola virus.
There is no cure for smallpox but the smallpox vaccine has proven to be one of the great public health success stories. Naturally occurring smallpox was eradicated by 1980 after an unprecedented immunisation campaign.
Indeed, smallpox is central to the history of vaccines. Edward Jenner, an English doctor, discovered that immunity to smallpox could be produced using material from a cowpox lesion. This is considered to be the first step on the road to modern immunisation programmes, and certainly paved the way to the eradication of smallpox.
Watch: History of smallpox eradication