Benedict Moran:

How the continent got that way is a long story that began when the first polio vaccine was introduced in the United States in the 1950s. The virus was last seen in America in 1979. But it remained devastating in much of the world, paralyzing more than 350-thousand people every year in one hundred twenty five countries as recently as 1988. In Nigeria, most cases of polio infection used to come from the north. Education here is lower than in the rest of the country. And misinformation about vaccines still exists here.