The Worm That Uses Your Pain

The Guinea worm grows up to three feet long inside the body, then forces its way out through a burning blister in the skin over weeks of agony.

That pain is the worm's plan. Desperate for relief, people plunge the wound into cool water, and at that exact moment the worm releases a cloud of larvae into it. The next person who drinks that water swallows the parasite, and the cycle begins again.

It may soon become only the second human disease ever wiped out, after smallpox, and the first beaten with no medicine at all.