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Tilkeshwar is one of India's forgotten villages.

It's 20 miles (30 kilometers) from the nearest paved road, untouched by electricity, running water, sanitation and even the barest of health care. Life is so bleak that nearly all adult men leave to search for menial work for their families' survival.

Here, deep in the floodplains of the Kosi River, the polio virus has stubbornly hidden. And it is here where the long-stalled global fight to eradicate the crippling disease might be on the verge of a badly needed victory.

The sudden optimism has been stoked by a startlingly effective campaign by the government and aid groups to finally drive polio out of India. The scale of the effort is staggering. In just five days last month, 2 1/2 million workers visited 68 million homes to inoculate 172 million children.

Similar campaigns have fallen short in the past, but two factors this time are different: Health workers are armed with a new, more effective vaccine, and nearly airtight monitoring means virtually no child is missed, not even in the most remote of villages.

For India, teetering between the worlds of poverty and new wealth, defeating a disease long forgotten in richer countries would be a crucial step in its transformation into a global power.

"It's a stigma for India," said Dr. Lakhindra Prasad, chief medical officer of India's Darbhanga district, which covers Tilkeshwar.

For the rest of the world, success in India would would create a precedent for bringing health services to even the poorest and most remote people.

"(It shows) what we think is impossible is actually possible in public health," said Bruce Aylward, the head of the World Health Organization's global polio campaign.

Across India, one of four nations where polio remains endemic, only 42 cases were recorded in 2010, a drop of 94 percent from the year before. It is the lowest number ever recorded here.

In the Kosi floodplains of central Bihar, there hasn't been a case since last January. In Uttar Pradesh, the other region in India where polio remains endemic, there hasn't been a case since April.

"We think the end of polio is near, we definitely feel it," said Dilip Kumar Mukhiya, a member of the Tilkeshwar village council.

India's near success, and a similar plunge in cases in Nigeria, has brought a surge of energy to the long-stalled global campaign against a disease that has paralyzed millions.

Last month, philanthropist Bill Gates pledged $102 million to eradication, which he called his top priority; Abu Dhabi's crown prince, Sheik Mohammed bin Zayed Al Nahyan, pledged another $50 million to vaccinating children in Afghanistan and Pakistan against polio and other diseases; Rotary International, which has already given more than $1 billion to eradication, unveiled a fundraising campaign entitled "This Close."

"This is the best situation I've ever seen," said Tim Peterson, a polio expert with the Gates Foundation. "I certainly think there's light at the end of the tunnel."

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The withered, twisted limbs of polio victims are common among the teenagers and adults of Tilkeshwar. One boy, who looks 10 but says he is 17, clings to a bamboo stick, his right leg bent and shriveled from the polio he got as a 6-month-old.

Lalti Kumari, a shy 3-year-old, limps alongside her grandmother. She had been vaccinated 12 times, but still caught the disease in March 2009, likely because malnourishment or diarrhea made the doses ineffective.

"I don't know how it happened," said her mother, Sharmila Devi.

Kumari's case is vexing but also represents hope — she is one of the last people to have come down with polio here.

The battle against polio dates back to the development of modern sanitation in the 19th century. This public health triumph stopped the spread of many fatal illnesses, but also turned polio from a relative rarity into a raging menace.

As contact with polio-laced sewage became less frequent, people no longer contracted the disease in early infancy, when side effects were rare. Suddenly, older children began succumbing to polio, which invaded their central nervous system and cursed its victims to a lifetime on crutches or in wheelchairs.

In the United States, families lived in fear of the summer, when the disease ran rampant. Parents kept their children out of public pools and movie theaters. Schools delayed opening until the outbreaks had subsided. Thousands were paralyzed or killed every year.

In 1953, Jonas Salk developed an injectable vaccine from dead polio virus. A few years later, Albert Sabin developed an oral vaccine from weakened, live virus that was even easier to administer. In the U.S. alone, cases plunged from 21,000 in 1952 to 61 in 1965.

In the 1980s, public health officials, giddy from their triumph in eradicating smallpox, turned their sites on polio.

The World Health Assembly started a global effort in 1988 to eradicate the virus by 2000. It was wiped out across the Americas by 1991; the Western Pacific by 1998; Europe by 1999.

But the drive stalled in Africa and south and central Asia. About 1,000 people a year fell prey to the disease, a huge drop from 350,000 before the campaign, but far short of eradication.

Polio proved to be far more elusive than smallpox, which brings a rash that makes those infected easy to locate. With polio, fewer than 1 percent of the infected fall ill, but they still spread the virus in their stool.

And the four countries where polio remains endemic presented other challenges. In Afghanistan and Pakistan, lawlessness and conflict made it difficult for vaccinators to reach children. In northern Nigeria, Muslim religious leaders boycotted the vaccine as a Western plot to sterilize their children. In India, malnutrition and chronic diarrhea made children too weak to properly process the vaccine.

Donors were losing patience with a program that has already cost nearly $9 billion, and requires another $750 million each year. But even as skepticism soared, victory suddenly seemed within reach in India.

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Early on a winter morning, Marta Dodri, a maternity ward nurse, trudged 20 kilometers through a frigid, pre-dawn gravy of dust and fog, crossing a patchwork of rivers and streams in rickety boats to reach Tilkeshwar. During the summer rainy season, when the streams swell to rivers, the swamps to lakes and the fields to mud, the villages become islands reachable only by long boat rides.

She has made the trip every month for five years to vaccinate the children here.

"I'm doing this because I want to get rid of polio. I want to do something good for society," she said.

Since 2009, the government, which runs this $300-million-a-year campaign with help from the WHO and UNICEF, has shored up efforts to finish off the disease.

It set up satellite offices across the Kosi floodplains, began monitoring every newborn to ensure they get the vaccine repeatedly and strengthened their surveillance so anyone with polio symptoms is swiftly tested.

During immunization drives, vaccinators in yellow vests go to schools, train stations, bus depots and roadside nomadic enclaves. The vaccinators are often female so mothers will trust them with their children. Health workers give zinc and oral rehydration solution to stop diarrhea and help children absorb the vaccine.

When they encounter resistant parents, vaccinators enlist community leaders — a neighbor, a teacher, an imam — to persuade them to relent. These efforts cut the number of children missed by each campaign from 14 percent before 2009 to less than 1 percent, said Dr. Ashish Satpathy, a WHO doctor assisting the program in Kosi.

"Nothing has been left to chance," he said.

When Dodri first started coming to Tilkeshwar, people ignored her. Now, they greet her and rush out to find their children.

"People understand that what we are doing is for them, and they help us, encourage us," she said.

The village is so poor, the children can't even find a ball to play cricket with, using an old plastic milk bottle and a stick instead. Half-naked children defecate by the road.

Dodri and her colleague Sanjana Shoba take along a cooler filled with ice packs and vaccine vials delivered by couriers who rode bicycles for hours over pitted trails to arrive here. The women methodically work their way to 60 homes of mud and cow dung.

In a small courtyard, 8-month-old Mousam Kumari is pulled off her mother's breast and given two quick drops of vaccine as she starts wailing. On a nearby rope bed, 5-month-old Gaurav Kumar sits with his grandmother. Shoba squeezes open his mouth and drops in the vaccine. Gaurav's brother, 5-year-old Neranjan, wanders in and gets a quick dose. Shoba colors their left pinky nails with an indelible purple marker to keep track of who has received the drops.

Dodri paints the date and a "P'' on the house, signaling all the children who live there are protected. She marks another with an "X," showing some have been missed. A supervisor follows to ensure no houses have been wrongly marked.

Later in the day, Dodri and Shoba will loop back to the "X'' houses to vaccinate the missed children. If any slip through, they come back again the next day.

Villagers complain that the vaccinators are the only health workers they ever see. One asked why they didn't bring other medicine; another demanded clean drinking water.

Rajkishore Tanti, a 45-year-old who estimates his two children were vaccinated roughly 50 times each, said the eradication program is the only government service that reaches the village.

"If the road department, the electricity department, all the other government departments functioned like this polio campaign, our plight would be over," he said.

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Perhaps the greatest change in the eradication campaign was in the vaccine.

The traditional formula targeted three polio variants, including one already eradicated, but was less effective against the remaining two. Last year a new vaccine aimed only at the remaining strains was rolled out. Infections plunged and hopes soared. In Nigeria, where religious leaders are now supporting vaccination, the number of cases dropped to 21 last year, from 388 in 2009.

Yet there have been false hopes before. In 2005, cases in India fell to 66 and many thought they were on the brink of victory. The next year, polio struck back, with 676 cases.

International experts urged caution, pointing to outbreaks that keep cropping up in countries where the disease had been eradicated. Polio erupted in Tajikistan last year, affecting 458 people and spreading to Russia, Turkmenistan and Kazakhstan.

"In the global sense, as long as it's anywhere it's not over," said Ellie Ehrenfeld, who sits on WHO's Advisory Committee for Polio Eradication. "As long as there is some place, some pocket, of poorly immunized people, it'll spread like wildfire."

Another problem is the oral vaccine itself, which causes polio in rare cases. The injectable vaccine doesn't have such side effects, but also costs 20 times more.

"The magnitude of the task of getting from where we are right now to the end should not be underrated," said Dr. Donald Henderson, who headed WHO's smallpox eradication program. "We have quite a ways to go."

Despite the challenges, Aylward, the head of the global eradication drive, said that for the first time, hope seems to be winning out. When the WHO board met last month, there were few of the usual impatient demands for a new polio strategy, he said.

"Everyone can see the numbers, everyone can see the big drops," he said. "Now they were saying, 'Gosh, this can be finished.'"