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Across the finish line

Makoy Samuel Yibi won’t stop until the world eradicates its next disease

Guinea worm once infected 3.5 million people every year. Thanks to heroes like Makoy, that number dropped to 13 last year.


When you see someone suffering from a terrible disease, it’s hard not to imagine a world where no one has to feel this way ever again. But the problem with eradication is that it’s really, really hard. The fewer cases remain, the more difficult it is to find them. That’s why, in all of human history, we’ve only eradicated two diseases: smallpox and the cattle disease rinderpest.

That might change soon.

The world is close to eradicating Guinea worm disease, a debilitating and painful condition that once devastated an estimated 3.5 million people in Africa and South Asia every year. Thanks to heroes like Makoy Samuel Yibi, that number dropped to 13 people in 2023.

As the national director of the South Sudan Ministry of Health’s Guinea Worm Eradication Program, Makoy helped reduce the number of cases in his country last year to just two. That’s a remarkable accomplishment by any standard, but it’s truly impressive when you consider the circumstances he and his team have faced: civil wars, the COVID-19 pandemic, the political changes brought by South Sudan’s decision to become an independent country in 2011, and the fact that the nation was once home to 90 percent of the world’s Guinea worm cases.

I recently caught up with Makoy at the COP climate conference in Dubai, where we both participated in an event focused on ending neglected tropical diseases, or NTDs, like Guinea worm. When you meet him in person, it’s hard to imagine a better person for the job. Makoy is passionate, brilliant, and laser-focused on making life better for the people of South Sudan. So I was surprised to learn that, as a young man, he never imagined a career in health.

Makoy was born in Terekeka County, a rural area located on the shores of the West Nile in southern Sudan. When he was a young man, Makoy had one primary focus: avoiding military service, which could be extremely dangerous. A chance meeting with a general from Terekeka resulted in a position with the national health department. A measles outbreak was ravaging parts of Sudan at the time, and Makoy’s first assignment was to travel from village to village providing care.

“What struck me,” he recalls, “was that, in every household we went to, we found at least half of the household was down with Guinea worm.”

The Guinea worm is a particularly nasty parasite. It’s unlikely to kill you, but the disease it causes—which is also called dracunculiasis, or “afflicted with little dragons”—can incapacitate you for months at a time and leave you permanently disabled. That can have devastating consequences if your family counts on you to grow the food you eat and sell it to make a living, as many people in South Sudan do.

The way the disease works is horrifying. If a person drinks water contaminated with Guinea worm larvae, the larvae enter the digestive system and mate. The impregnated female worm grows, undetected by the body’s immune system. Around a year later, the infected person will start to feel an itch somewhere on their body (usually the lower leg or foot). After a couple days, a painful blister appears and eventually bursts. The worm—which is now about one meter long—slowly starts to emerge from the wound.

This can take weeks or even months, and the pain it causes is excruciating. The wound can get infected, which could result in permanent disfigurement or even require amputation. And people often endure multiple worms emerging at the same time. Makoy has seen patients with as many as 40 worms.

And here’s the most insidious part: One of the few ways to relieve the pain of the blister is by soaking it in cold water, like a pond or a puddle. But that’s exactly what the worm wants. As soon as it touches water, it releases its larvae, starting the cycle anew. The Guinea worm is scarier and more efficient than any monster in a horror movie.

Makoy has seen countless times how devastating Guinea worm can be. “This is a situation where you see serious disruption of the livelihood of the community,” he says. “You see people going through a cycle of hunger because they don’t have enough. They have lost the window of cultivation. They’re not able to tend to their cattle, and there’s nothing they can do.”

There is no cure or treatment for Guinea worm, and yet, the world is on the doorstep of eradicating it. How? Through a series of highly effective interventions and a network of incredibly dedicated health workers.

"Makoy’s team has built a network of volunteers in virtually every village in the country."

Makoy’s team has built a network of volunteers in virtually every village in the country, who report rumors of Guinea worm cases. They spend every day searching for cases, getting the word out, and building trust in a country where more than 60 languages are spoken.

Makoy and his colleagues investigate every single rumor, no matter how remote. During the rainy season when the majority of cases happen, he often spends days hiking through the Sudd or up a mountain with all of his supplies on his back just to reach his destination. Last year, in a country the size of France with less than 100 miles of paved road, the team responded to nearly all of the 50,000 rumors they received within 24 hours.

Once the team finds a confirmed case, they make the patient as comfortable as possible and do what is called “controlled immersion.” This means soaking the affected area in a bucket of water and encouraging the worm to come out.

Makoy also spends a lot of time preventing people from getting Guinea worm in the first place. His team distributes free water filters and educates communities about safe water practices. The system they’ve built to support this work has strengthened health systems across the country, providing a platform for delivering other health services like childhood vaccination.

Makoy’s team has had a tremendous partner in all of this work: former U.S. President Jimmy Carter and the Carter Center. In 1995, when Makoy was first starting his public health journey, President Carter negotiated what remains the longest humanitarian ceasefire in history when he helped convince both sides of the Second Sudanese Civil War to lay down their arms and allow health workers access to treat Guinea worm and other diseases, like polio and river blindness. Today, the Carter Center continues to lead the global eradication campaign’s march to zero. The Gates Foundation is proud to support the Carter Center as part of our overall efforts to tackle NTDs. (You can learn more about Makoy’s partnership with the Carter Center in a new film called The President and the Dragon that is coming out later this year.)

Eradication is now within sight, although it won’t be easy to eliminate the last few cases. South Sudan previously reported no Guinea worm in 2018, but cases were subsequently discovered after a peace agreement was reached in the South Sudanese Civil War. And Guinea worm has recently been detected in dogs and other animals, mainly in Chad. Eradication will require stopping all transmission, both human and animal.

But Makoy Samuel Yibi is optimistic we can get there—and so am I. His determination to root out every last case makes me hopeful that we will someday soon celebrate the end of Guinea worm disease.

“In the places where Guinea worm has been eliminated,” he says, “you can actually see how communities have been energized. They are more active, and they are productive. The communities are now empowered to be more self-sufficient, because they don’t have to worry about Guinea worm.”

Meet more of my heroes in the field