JOHANNESBURG -- A new report says the world is moving closer to eradicating Guinea worm disease, in which a meter-long worm slowly emerges from a blister in a person's skin.

The U.S.-based Carter Center, which leads the eradication campaign, says just 30 cases were reported last year in isolated areas of Ethiopia and Chad. All 15 cases in Ethiopia occurred at a farm where workers drank unfiltered water from a contaminated pond.

Mali has not reported any cases in 25 months, and civil war-torn South Sudan has reported no cases in 13 months. The Carter Center called that a "major accomplishment."

The incapacitating disease three decades ago affected more than 3 million people in 21 countries in Africa and Asia. The meter-long worm incubates in people for up to a year before painfully emerging, often through extremely sensitive parts of the body.

"It was more painful than giving birth," one South Sudan resident, Rejina Bodi, told The Associated Press last year. "Childbirth ends but this pain persists."

Unlike other diseases which are controlled by medicines or vaccines, Guinea worm can be eradicated by educating people how to filter and drink clean water.

Globally, the Guinea worm program is entering the final stretch, though the World Health Organization warns that the remaining cases can be the most difficult to control as they usually occur in remote and often inaccessible areas.

If South Sudan continues to report no cases, the world's youngest country will be on track to be certified Guinea worm-free in the next couple of years. In an interview last year with the AP, former President Jimmy Carter praised South Sudan for making steady progress despite the "tremendous problems" in the East African nation.