There were only 542 known cases of Guinea worm worldwide as of 2012, representing a 48 percent drop from 2011, CNN reported.
"We cannot rest until we get and contain the very last case," Dr. Donald R. Hopkins of the Carter Center in Atlanta, which has led the effort to wipe out Guinea worm, said Thursday.
The disease, also called dracunculiasis, gets into the human body when people drink water contaminated with water fleas that have ingested Guinea worm larvae. The human stomach kills the water fleas, but not the larvae within and worms pass through the intestinal wall and under skin tissues.
A patient develops a skin blister, through which a worm will emerge about 10 to 14 months after infection. The worm can be as long as 3 feet and looks like a long spaghetti noodle.
South Sudan has the most known cases today, at 521, said the Carter Center, a non-profit organization founded by former President Jimmy Carter that started working to eradicate Guinea worm in 1986.
Carter said the main obstacle in eradicating Guinea worm is that if a case is not treated properly, it can quickly spread from one person to hundreds. Communities that depend on open water sources in rural and isolated areas are especially affected, the World Health Organization said.
The international effort is watching about 7,000 villages that are at risk, he said.
"We need to find anyone who has Guinea worm" and "prevent them from going back to the water source," Carter said.