President Jimmy Carter spent four years in the Oval Office, but his legacy extends far beyond the White House. The former head of state died on Sunday, December 29, in his home in Plains, Ga., aged 100, after nearly two years in hospice care. In the decades since he left public office, Carter delivered a significant contribution to public health in the worlds poorest nations.Carter served as president from 1977 to 1981; in 1982, he established the Carter Center with his wife, Rosalynn, who died November 19, 2023 at age 96. The humanitarian organization advocated for setting international standards for human rights, strengthening global democracy by observing elections in 39 countries, and establishing village-based healthcare in poverty-stricken nations. Carter advocated for and built affordable housing for 30 years with Habitat for Humanity, and he won the Nobel Peace Prize in 2002.Also integral to Carters humanitarian work was controlling and eradicating diseases afflicting masses of people in the global south. In particular, the Carter Center has helped to all but eradicate the excruciating Guinea worm disease, reducing the 3.6 million cases from the 1980s to just six today. Carter played a hands-on role, personally visiting remote villages to meet with both leaders and ordinary people alike, and launching a program of disease prevention and education that now extends far beyond Guinea worm.Trips to Nigeria and Ghana, where Carter saw various diseases decimating entire villages, would spur him to launch campaigns to end these neglected tropical diseases (NTDs), a group of 20 severe ailments that affect 1.2 billion of the most marginalized people, but which are ignored or unheard of in much of the West. Its unfortunate, because this affects the poorest of the poor, says Kelly Callahan, director of the Trachoma Control Program at the Carter Center.Former president Jimmy Carter visits the Central Equatorian Sudanese village of Lojura on February 11, 2010. [Photo: Petter Martell/AFP/Getty Images]Callahan, who has worked at the center for 25 years, says Carter wanted to tackle these diseases precisely because they were so neglected, and because many other problems stem from them. They debilitate people to the point where they cant work for weeks and months, causing further insecurity for the poorest families. He really saw these neglected tropical diseases as low-hanging fruit toward reducing the gap between the rich and the poor, Callahan says.The biggest priority on Carters list was Guinea worm disease, prevalent in 20 countries mainly in Sub-Saharan Africa. Known as dracunculiasis (Latin for little dragons), its caused by parasites in drinking water. Once ingested, water fleas release worm larvae inside the human body, which live and mate in the connective tissues of the abdomen. The female pregnant worm can grow up to three feet in length and be as wide as a strand of cooked spaghetti. When the female worm is ready to release the larvae (roughly one year after the initial infection), she moves just below the skin to give birth (usually to the leg or foot), forming a painful blister that eventually bursts, which can cause further bacterial infections.Guinea worm disease is highly transmissible. If an infected person enters wateroften to bathe their painful woundit triggers the worm to release millions more larvae into the water, ensuring the disease continues to proliferate.Farmer Nuru Ziblim teaches children how to filter their water with a special drinking device, when visiting the farms, so as to not ingest the guinea worm larvae, ca. 2008. [Photo: Louise Gubb/Corbis via Getty Images]He could not believe in the 1980s that people still had 3-foot-long worms coming out of them, Callahan says.Carters Guinea worm campaign centered around prevention and education, really the only route for a disease that still has no known cure, vaccine, or medication. The center worked to treat standing water with a larvicide and distribute water filters.Callahan first met Carter in Mali in West Africa in 1996 when she was a Peace Corps volunteer. She found Carters on-the-ground presence unusually refreshing, as he traveled to remote villages around Africa to see the diseases impact for himself. He wanted to set an example for others, that it is possible to roll your sleeves up, Callahan says. He needed to hold hands and bring people along with him.He harnessed his influence to negotiate a deal with chemical corporation DuPont to develop the water filters for free. And in 1995, he called a four-month cease-fire of the brutal civil war in Sudan to allow the distribution of enough filters for every citizen.The disease dissipated over the following decades, from 3.6 million cases globally in the 1980s to an all-time low of 13 as of January 2023. Through prevention alone, the center eliminated the disease in 17 countries.But to eradicate, it requires staying the course. (Elimination refers to curbing a diseases transmission within a specific area; eradication to wiping it out completely.) If [the center] took [its] foot off the pedal, this disease will come back, and it will come back with a vengeance, Callahan says. It takes two years from identifying zero cases in a country before they can certify it as free of the disease.The center is working toward eradication, and Callahan is optimistic that the 13 can become zeroan important part of continuing the legacy of the man who wanted to see the disease wiped out before his death. It is completely possible, she says. And not just possibleit is going to be eradicated.Part of honoring Carters legacy will be continuing that work on other diseases as well. The center works to control other NTDs including trachoma, the worlds leading cause of infectious blindness, on which Callahan focuses. Since the centers work on trachoma in 1998, cases have diminished from a billion to 125 million.If the Carter Center gets its way, Callahan says, well turn it into an elimination program, and then an eradication program.