When polio vaccines were first developed, many experts thought the disease would be fully eradicated within decades. Tragically, as this film shows, it has survived in places like Afghanistan and northern Nigeria.
These locations are now acting as disease reservoirs, with children the hardest-hit demographic and with travellers re-infecting other countries once thought invulnerable.
Additionally, in the pre-vaccine world, everyone had a degree of natural resistance to polio, but now, after decades of immunization, most Westerners have none. And with polio just a distant memory to most people under age 50, immunization rates are falling, and the disease, which can cause total paralysis in a matter of hours, is poised for a comeback.
Despite the vital efforts of the WHO and other groups, is the world fighting a losing battle against the disease?
This film is part of the KILL OR CURE series of 57 x 25-minute documentaries produced for the BBC. These films can be bought individually or as a series.