Nigerian President Goodluck Jonathan imposed states of emergency in three states Wednesday, promising to send more soldiers to the northeast to put down a growing threat from militants from the Islamist group Boko Haram group and an offshoot, Ansaru.
Some critics say that ending polio has become Bill Gates' "white whale."
Why not just settle for the huge drop in polio cases that we've seen over the past decade and then spend money on other things that kill so many more kids, like diarrhea and malnutrition?
"Polio is special," Gates tells NPR's Robert Siegel on All Things Considered. "Once you get it done, you save $2 billion a year that will be applied to those other activities. There's no better deal economically to getting to zero."