For all of the mind-boggling achievements of modern medicine, only one -- one! -- disease has ever been completely eradicated: smallpox.

But now guinea worm -- the preventable disease that forces people to live with worms up to three-feet long inside them -- is teetering on the brink of joining that very, very short list of diseases.

"Guinea worm disease is fewer than 1,800 cases away from becoming only the second disease in history to be wiped from Earth," said former President Jimmy Carter, yesterday, at an awards ceremony for his eponymous center.

Back in 1986, when the Carter Center began waging war on the disease, some 3.5 million people had Guinea worm in more than 20 nations. Now, after a 2004 World Health Assembly meeting calling for an "intensification of eradication activities," and the continued efforts of UNICEF, the CDC and the Carter Center, it is confined to the Southern Sudan, Mali, Chad and Ethiopia. (According to the CDC, Ghana may have recently conquered the disease.)

Guinea worm is a parasitic infection that is transmitted in unfiltered water or from stagnant surface waters. According to the CDC, people with guinea worm larvae feel no symptoms for about a year, during which time the worm incubates. Thereafter, they begin to feel nausea and dizziness and a blister develops -- typically in the lower part of the body. When a person puts the affected area into water to soothe it, the worm bursts out, releasing larvae back into the water.

All of which make guinea worm an incredibly difficult disease to eradicate. There is no vaccine and the only way to prevent its spread is to keep people with active infections from going into bodies of water and re-infecting them. Which is basically what has been done.

But even as we near the possible historic event of wiping out guinea worm, the difficulties of complete eradication are never far from mind.

"The last cases of any disease are the most challenging to wipe out," said Carter Center vice president of Health Programs and smallpox expert, Dr. Donald Hopkins. "Especially when stability is threatened in the endemic communities of Southern Sudan and Mali."

