Stamping Out Polio Polio -- a once-dreaded scourge -- is nearly gone. Cases are down from hundreds of thousands a year in the 1980s to fewer than 700 last year. But, as NPR's Joanne Silberner reports, the endgame is proving difficult. The audio for this segment contains an error. It should have said that Nigeria's national government is led by Christians, but Christians do not make up a majority of the population. Various estimates indicate the country is 50 percent Muslim, 40 percent Christian, 10 percent indigenous.