Quotes of the Day

The stone houses of Safal Bandi in Pakistan's remote Swat Valley have changed little over the past century. The only indication of the passage of time is a series of dates, six weeks apart, chalked on the door of each house. Parwanna Begum steps from behind one of those doors and adds today's date to the list, followed by a fraction: 2/3. Out of three children under the age of five in the household, Begum, a local health worker, has vaccinated two against polio. The third is out playing. Begum will have to come back tomorrow, because one child missed in the nationwide vaccination campaign means a hole in the net the world is trying to throw over the crippling disease.

This year, health workers are the closest they have ever been to eradicating polio—a virus that in 1988 was paralyzing 350,000 children a year—largely due to the efforts of hundreds of thousands of volunteers like Begum participating in a global vaccination program. In 2003, only 784 cases were reported worldwide. But a recent surge of new infections in Africa is raising fears that wiping out the disease may be just beyond humanity's grasp. Three years ago, Africa was on track to meet the World Health Organization's (WHO) objective of a polio-free planet by 2005—only 82 cases were reported. A year later, new cases had almost tripled, with most occurrences in Nigeria, after immunizations were curtailed due to rumors that the program was a Western plot to sterilize Muslim girls. By the end of 2003, another 447 children in Africa had been paralyzed, and health officials are worried the tide has turned against them. "This year is the real nail biter," says Dr. Bruce Aylward, coordinator of the WHO's polio-eradication program. "Under a thousand cases is an unnatural state for an epidemic disease. Either we force it down to zero, or it is going to blow up and paralyze hundreds of thousands of children every year."

Although the virus that causes polio is highly contagious, bringing it under control is relatively straightforward because a cheap vaccine has long been available. "There is no magic to this," says Dr. Tumseh Salah, who is managing the Swat Valley vaccination program. "You immunize enough kids, and you can stop the virus." Indeed, the eradication program has been a spectacular success. In its 16 years of operation, the number of countries where polio remains a chronic problem has fallen from 125 to just six: Egypt, Niger, Nigeria, Afghanistan, India and Pakistan. (In all of Asia, just 34 cases were reported in the first six months of the year.) But a vast and unstinting effort is required to achieve and maintain those results. In Afghanistan, Pakistan and India, the WHO works with governments and UNICEF to coordinate immunization drives involving thousands of local health workers and volunteers. Every six weeks, they fan out through cities and villages, each worker carrying a thermos of vaccine vials, roughly drawn maps and a clipboard to chart their progress. "It's like running three national elections eight times a year," says Aylward, "only you are going to the houses rather than bringing kids to the voting booths."

And like voting drives, immunization programs are vulnerable to political winds. In 2001, India was on the verge of becoming polio free—just 268 cases were reported that year. Encouraged by the progress and eager to reduce the $100 million annual cost of funding the program in India, the government scaled back the number of vaccinations. The following year there were 1,600 new victims. A renewed immunization campaign has brought cases down again, but the incident demonstrated how quickly progress can be undone.

Indeed, some question whether the polio program makes economic sense. The WHO estimates that 5 million cases of polio have been averted since 1988. But $3 billion was spent achieving that result—or $600 for every case avoided. Critics say the money would be better spent attacking deadlier diseases such as malaria, which kills at least a million a year.

Salah, a trained epidemiologist, says the value of the program is greater than the number of prevented cases. Health workers have created a game plan that can be applied to other scourges. "With this campaign, we have gathered a huge body of practical, field-tested methods on how to eradicate a disease," he says. "Once we develop vaccines for TB, SARS, HIV or malaria, we will be able to use these methods to add even more to the health of humanity."

But if you don't knock out polio first, he adds, it may all be for nothing, and the WHO must keep the pressure on. In the past 18 months, 77 new cases have appeared in nine African countries that were previously polio free. Another has just surfaced in Darfur, Sudan, bordering Chad, where refugee camps are a tinderbox of cramped quarters and unclean water. The world, says Aylward, is like a forest, and one polio case can touch off a wildfire that may take years to put out. "We have gone several seasons without [a forest fire]," he says, "and the brush has gotten dryer and dryer. One spark, and it could explode anywhere."

• Aryn Baker | Safal Bandi
• A new outbreak of polio in Africa underscores the difficulty of wiping out a stubborn global scourge