Guinea worm is about as close to a real-life Alien event as you can get — a parasitic worm mates inside a person's abdomen, grows up to 3 feet long and then exits (painfully) from a blister.
But the worm's final chapter is near: The world is closer than ever to wiping the parasite off the face of the Earth.
There were only 17 cases of Guinea worm in the first five months of this year, the Carter Center reported Monday. That's a 75 percent reduction from this time last year, when 68 people reported infections.
Back in the mid-'80s, more than 3 million people were catching the parasite each year. Then an international campaign started slashing cases, year after year.
"We anticipate we'll end 2014 with less than 100 cases," says Dr. Ernesto Ruiz-Tiben, who leads the Guinea worm eradication effort at the Carter Center. "The data speak for themselves. Great strides have been made against Guinea worm."
Now Guinea worm has been eradicated in 17 of the 21 countries where it ever existed. And the worm has cropped up in only two countries this year: South Sudan and Chad.
Most of us aren't familiar with Guinea worm. (It's never existed in the Western Hemisphere.) But once you hear how it infects people, you probably won't forget it.
The parasite lives in tiny fleas swimming in fresh drinking water. When someone accidentally swallows a flea, the worm's larvae are released inside the person's stomach.
The larvae mate and mature inside the abdomen. Then about a year later, a painful blister appears on the person's skin, often on a leg or a foot. A long worm slowly emerges from a hole.
The worm doesn't usually kill you. But its exit is debilitating and excruciatingly painful. To remove the worm, a health worker winds it around a small stick and manually pulls it out of the skin over the course of a few weeks. During the process, a person usually can't go to work or school.
The disease is also known as dracunculiasis, or "affliction with little dragons," because the worm feels like tiny, hot daggers poking through skin. This burning sensation makes a person want to dip the blister into cool water, such as a lake or river. Then the worm releases a fresh batch of larvae into the water. And the infection process starts all over again.
There is no cure or vaccine for Guinea worm. So the Carter Center, together with local health agencies, has focused on stopping the parasite's spread. They teach people to filter water, and they dig wells for clean drinking water.
When health workers hear about an emerging infection, they rush to the village to make sure the person doesn't infect local water sources. The health workers also kill water fleas with insecticide in potentially contaminated lakes or rivers.
Guinea worm requires humans to complete its life cycle. So once the parasite is wiped out of people, it will be extinct.
The challenge now, Ruiz-Tiben says, is finding the last few and far-flung cases before a person spreads the worm. "These cases are in very remote parts of the world," he says. "We have a monetary award set up: A person can get $100 if they have information about infections, or if they're infected themselves. So that helps with surveillance and awareness."
Twelve of the 17 Guinea worm cases this year have occurred in one small pocket of Eastern Equatoria State, South Sudan. Luckily, Ruiz-Tiben says, this region is far away from the recent violence in the young country. So health workers have been able to continue treating cases there despite the civil war.
So when will Guinea worm be gone for good?
"It's conceivable that we could have zero cases in 2015," Ruiz-Tiben says. "But if I was a betting man, I would say that we have a 60 to 40 percent chance of getting to zero there in 2015. Our chances the following year are much higher."
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