Through the heaving crowd of a Delhi railway platform, Vandana Saini spots a sleeping toddler slumped on her mother's shoulder. She darts forward brandishing a tiny squeeze bottle. "Polio?" she hollers over the screech of train brakes, inspecting the baby's fingernail for the tell-tale ink mark that shows the recently vaccinated. The mother shrinks back for a moment, then recognizes Ms. Saini's yellow vest, the sign of India's 2.3-million volunteer vaccinators. She nods assent and tips the baby's head off her shoulder. As the crowd eddies around them, Ms. Saini expertly squeezes the baby's cheeks until her mouth opens, deposits two drops of vaccine, marks the fingernail and sends the family onward, pivoting on her heel to spot the next child.
She will squeeze and drop, squeeze and drop each day this week, as she has tens of thousands of times before in her 10 years of working with India's polio eradication effort. She patrols the platforms and she rides the trains, working her way from car to car until she has done all the children, then disembarks and gets started on the next train back - seven or eight trains in a day.
This way, the polio team hopes, she will catch impoverished economic migrants flooding into the city. They come from villages with no sanitation to slums with no sanitation and they are most likely to carry the virus and be missed in a door-to-door campaign. An army of volunteers is at work this week at every rail station, every bus depot, every major crossroad outside the megacities; they aim to inoculate 174 million children.
The train-station campaigns are an Indian innovation, one of several new approaches that have helped to get this country achingly close to a goal that has seemed, for years, unobtainable.
Polio is all but gone from India, from this gigantic nation that has been the source for most of the critical new outbreaks in recent years, its last stand winnowed down to just two or three areas no bigger than 30 square kilometres.
"We have it on the ropes," said Bruce Aylward, the Canadian who has directed the World Health Organization's global polio eradication program for more than a decade.
Yet India's moment has gone unnoticed by a world bored with the "this-close" narrative of polio. This has critical implications: The fight against polio is all but bankrupt - short of $720-million (all figures U.S.) for 2011-12, despite hearty promises from G8 countries to keep the effort well-funded to the end.
A high-powered partnership has formed around polio eradication in recent years, its great new champion software tycoon Bill Gates, who calls this ambition his "number one priority" and whose foundation has put in $760-million in the last three years. And the WHO, UNICEF and Rotary International are equally engaged. India itself injects $300-million a year into the fight. But without the cash to continue, the partnership will have to curtail efforts to boost coverage.
Dr. Aylward and other experts understand the donor frustration - year after year, polio cases decline in some countries, but swell in others, while the overall cost of the campaign nears $10-billion. "The program seemed to stall on the precipice of eradication," said Hamid Jafari, the director of the WHO's India team.
But the experts have a worry of their own: this time, it really is different. India has had just one polio case in 2011, and only six in the past six months. And if it's possible here, "You can do it anywhere," Dr. Jafari said.
India's fight against polio holds two lessons for the rest of the world: the first concerns the perils of getting close to wiping out the virus, but not all the way there - and the second, the progress that is possible with a combination of political will, a healthy budget and scientific and social innovation. The poliomyelitis virus, which can cause life-threatening paralysis in just hours, was once a global scourge.
After Jonas Salk found a vaccine in 1953, fears of polio began to ebb in the developed world; a global eradication effort began in 1988, and the virus was gone from the Americas in 1991. By 1999, it remained only in a handful of countries in Central and South Asia and Africa.
Before the eradication campaign, India saw as many as 50,000 to 100,000 cases a year, but by 2005, it was down to just 66. But as the number waned, so did vigilance. The virus resurged the following year with 676 cases - many of them Indians who migrated, either within or without the country, taking the virus back into areas where it had long been eradicated, or abroad.
Microbiologists can "fingerprint" a virus can tell, based on its genetic makeup, where it came from - right down to the neighbourhood.
So we know that a 2007 outbreak in Angola, which had been polio-free, came from India. Then the virus spilled over the Angolan border into the Democratic Republic of Congo and then Congo-Brazzaville - two countries from which polio had been chased out, but where weak public-health systems and low vaccination coverage made it difficult to contain the new epidemics.
Meanwhile, two reservoirs of wild polio virus survived here: one in western Uttar Pradesh, the other in central Bihar. These two states in northern India are among the poorest and most populated. Some 500,000 new babies are born in Uttar Pradesh every single month, yet less than half of these are born in medical facilities where they might get the vaccine. In Bihar, the virus lurks in the Kosi River floodplains - a teeming area where people live with little no access to basic sanitation services or public health.
Dr. Jafari sends teams of vaccinators on motorbikes into the river delta, where they heave the bikes onto small boats to move between communities and then trek from each village eight or 10 kilometres out to a barsa, where people keep children in rough lean-tos to help stake a claim to land recently flooded with fertile silt. All the way, they lug ice chests with the vaccine, which quickly breaks down at room temperature. "There are more than a million children under the age of five on the Kosi River embankment alone," he said.
Teams infiltrated the most inaccessible areas, and repeatedly vaccinated more than 90 per of children. In most places, that is enough to quash polio, but not in Kosi or Uttar Pradesh. "Here you need at least 95 per cent - in an area with extremely high population density and zero public services," Dr. Aylward said. "It's like having to run the 100 meters two seconds faster than anyone else in the Olympics."
No one knows why the vaccine works only half as well in these areas. The extremely high levels of diarrhea in children? The profusion of other bugs in their gut? But they needed a new plan.
Polio comes in three distinct strains. The vaccine used in most of the world targets all three. In northern India, that vaccine wiped out Type 2, but didn't work as well on 1 or 3. So the polio campaign decided to revert to type-specific vaccines used in the early days of immunization. But whenever they drove Type 1 back, 3 flared up; when they quashed 3, then 1 came back. Dr. Jafari likened it to a vicious game of Ping-Pong.
This called for a new vaccine, one that would work against Types 1 and 3 simultaneously, without, in lay terms, cancelling each other out.
Normally the production of a new vaccine would be years in the making. But the WHO teamed up with India's Medical Research Council and local pharmaceutical firms to design a vaccine that worked on Types 1 and 3 - and they were using it on children in just six months. "The commitment of the government of India and the state governments is incredible - India is the only country that funds more than 80 per cent of its polio program," Dr. Jafari said.
The Indian government reported just 42 cases last year - down 94 per cent from the year before, and the lowest number ever recorded here.
That news is, in a way, even better than it sounds: In the entire high-transmission season, which comes with the summer monsoon, there was not a single case in Uttar Pradesh, and just three in Bihar. From nine distinct genetic clusters of Type 1 polio virus in 2006, there is now just one.
"We've never been this close," Dr. Jafari said, his voice lowered, as if not to tempt fate. "We've never seen this picture before."
That said, the fight is not over in India: there was an unexpected, fast-moving outbreak in West Bengal last year caused by a virus from Bihar. But an extensive "mop-up operation" is under way there now, before the rains come, and if no new cases are reported for 18 months, India will be removed from the list of four countries where polio remains endemic.
One of the holdouts is Nigeria, which had a sharp flare-up in cases after 2003. In Nigeria, state governments banned vaccination when rumours spread that the polio vaccine was actually being used to sterilize Muslims. The virus spread from Nigeria back into 12 countries that had wiped it out. Heavy lobbying persuaded Islamic leaders to urge people to co-operate with vaccinators. Nigeria reported just 21 cases in 2010, down from 388 cases in 2009. Experts believe eradication may be possible there soon.
The last two endemic countries are Afghanistan and Pakistan. Despite the weak state and vicious fighting in much of Afghanistan, a team there has successfully negotiated with warring factions to allow access to children.
India will need to maintain the rounds of mass vaccination for a few years, to keep herd immunity high - and also redouble efforts at surveillance, so that if a new case pops up, it is caught immediately.
The surveillance network investigates all reported cases of acute flaccid paralysis, the tell-tale sign of polio - some 55,000 a year.
The WHO team regularly reminds doctors in hospitals and private practice to call their hotline the moment they see a limp-limbed child. It also cultivates relationships with herbalists, village healers and temple priests, to whom poor people often take sick children first.
The cause is not without dedicated backers: Mohammed bin Zayed Al-Nahyan, the crown prince of Abu Dhabi, recently pledged $50-million to vaccinate children in Pakistan and Afghanistan, while the Gates Foundation has pledged another $450-million for the next two years.
But, Dr. Aylward said, it isn't enough: they need the world's richest nations to pitch in further. In 2005 (and many times since), the G8 member countries pledged to maintain or increase their contributions, yet G8 contributions for 2011-12 account for just 12 per cent of the global campaign's $1.86-billion budget, compared with 58 per cent in 2004-05.
Walter Orenstein, a polio expert with the Gates Foundation, called this the greatest threat: that in an era of economic downturn, donors will think that almost eradicating polio sounds good enough. "We will get periods of silence," he warned. "And then outbreaks like in Congo or Tajikistan."
The budget shortfall means that Dr. Aylward is "cutting corners" in vaccine rounds in Nigeria, scaling back a vaccination campaign in Congo and restricting surveillance in India. It's risky. And if the disease isn't wiped out, he said, when the world came this close, it will stand as a stark rebuttal to the idea that all children are created equal. "If we don't end polio now, we're not saying it's because we can't, we're saying, 'It ain't worth it.' Because now, we have no excuse. Now we know it's doable."