Polio was once the scourge of young people the world over, a horrific virus (officially known as poliomyelitis) which results in paralysis and slow suffocation of the muscles, it affected hundreds of thousands of children in the Twentieth Century.
The good news is that since the introduction of a vaccine in the United States in 1955, numbers have fallen to almost nothing in the developed world. This resulted in a subsequent worldwide decline of cases, although some countries still reported incidents. Afghanistan, Pakistan and Nigeria all reported cases of Polio amongst their young people, but those numbers have significantly declined. Nigeria was officially announced as being Polio free in 2015, which brings us another step closer to eradicating the review for good.
The WHO has established the Polio Eradication and Endgame Strategic Plan 2013–2018, which, if successful, will see the disease wiped off the face of the earth. This has only happened once before in history, when Smallpox was eradicated in 1977.
A more detailed account of this process by Phil Plait is available in Slate Magazine.