Many people, former U.S. President Jimmy Carter among them, consider Hopkins a hero. It’s easy to see why: As a young public-health worker, the soft-spoken Bahamian-American doctor was instrumental in the global effort to eradicate smallpox. He stopped its prolific spread in Sierra Leone in less than two years—a then-unthinkable feat of eliminating a contagious disease from the planet. Then, in 1980, he resolved to rid the world of Guinea worm disease (GWD), an awful but entirely preventable condition that annually afflicted 3.5 million people in Asia and Africa. GWD is usually not fatal, but it is painful and debilitating, the sort of scourge that strikes entire villages and, for months at a time, can bring school, commerce, and farming to a halt.

Hopkins, who is 76 and still at it—human transmission of GWD has been stopped in all but two countries, Chad and Ethiopia—says his biggest foe has been “failure of imagination.” Early on, people didn’t think the disease could be eradicated; others argued going after a non-killer like GWD was a waste of time and money. Thanks to Hopkins, whose data-driven playbook involves educating communities and motivating (and sometimes shaming) political leaders, GWD will likely be the second disease ever, after smallpox, to disappear from the planet.