For more than four decades after leaving the White House, President Jimmy Carter channeled his work on the world stage through his nonprofit Carter Center.

One of the key achievements, the near-eradication of Guinea worm disease, which once affected 3.5 million people. Last year, there were just 14 cases reported in Africa.

That's why, as William Brangham reports, Carter's work promoting global public health is being remembered by many as a core piece of his legacy.