THE MOP-UP.(polio in India)

The index case was an eleven-month-old boy with thick black hair his mother liked to comb forward so that the bangs rimmed his round face. His family lives in the southern Indian state of Karnataka, in a village called Upparahalla, along the Tungabhadra River. Dry mountains of teetering rocks can be seen in three directions from the village. It has no running water and little electricity. The boy's mother is illiterate; the father can read only road signs. They are farm laborers, and they live with their three children in a single-room hut of thatch and mud. But the children are well nourished. The mother wears gold and silver earrings. Once in a while, they travel.

In April last year, the family took a trip north to see relatives. Shortly after they returned, on May 1st, the boy developed high fevers and racking bouts of nausea and vomiting. His parents took him to a nearby clinic, where a doctor gave him an antibiotic injection. Two days later, the fevers subsided, but he became unable to move either of his legs. In a panic, the parents took him back to the doctor, who sent him to the district hospital in Bellary, about forty miles away. As the day progressed, the weakness spread through the boy's body. His breathing grew shallow and labored. He lay flat and motionless in his hospital cot.

A doctor at the hospital, following standard procedure in cases of sudden childhood paralysis, phoned a surveillance medical officer with the World Health Organization in Bangalore, the capital of Karnataka. The medical officer made sure that proper cultures were taken and sent to a national laboratory in Mumbai. On June 24th, the laboratory results came back. A young technical officer with the W.H.O. in New Delhi got the call; it was a confirmed case of polio, a disease thought to have been eliminated from southern India, and it set off an alarm.

The World Health Organization is in the sixteenth year of a campaign to eradicate polio from the world. If the campaign succeeds, it may be mankind's single most ambitious accomplishment. International organizations are fond of grand-sounding pledges to rid the planet of this or that menace. Such pledges make the organizations feel that they are doing something important. But they nearly always fail. The world is too vast and too various to submit to dictates from on high.

A handful of serious attempts have been made to eliminate individual diseases from the world. In 1909, the newly established Rockefeller Foundation launched the first global eradication campaign, an effort to end hookworm disease, using anti-helminthic drugs, in fifty-two countries. It didn't work. Today, a billion people--a sixth of the world's population--are infected with hookworm, an intestinal parasite that feeds on human blood. A seventeen-year campaign against yellow fever, led by the Rockefeller Foundation and the United States armed services, had to be abandoned in 1932 when yellow fever was found to have a reservoir outside human beings. (The yellow-fever virus persists in mosquitoes' eggs.) In 1955, the W.H.O. and unicef began a campaign to end yaws, an infectious disease causing painful, purulent skin ulcers; workers screened a hundred and sixty million people in sixty-one countries for the disease, and treated every case they found with penicillin. A dozen years later, the campaign was dropped when it turned out that silent, subclinical infections were continuing to propagate the disease. Billions of dollars were spent in the fifties and sixties to eradicate malaria; today the disease afflicts more than three hundred million people a year.

In the course of a century, the only successful attempt at disease eradication has been the battle against smallpox--a mammoth undertaking that was, however, decidedly simpler than the campaign against polio. Smallpox, with its distinctive blisters and vesicles, could be easily and quickly identified; the moment a case appeared, a team could be dispatched to immunize everyone the victim might have come into contact with. That strategy, known as "ring immunization," eradicated the disease by 1979. Polio infections are far harder to identify. For every person who is paralyzed, between two hundred and a thousand infected people come down with little more than a stomach flu--and they remain silently contagious for several weeks after the symptoms abate. Nor is every case of childhood paralysis polio; and it usually takes a couple of weeks for stool specimens to be obtained, delivered to a laboratory, and properly tested. By the time one case has been identified, scores more people have been infected. As a result, the area targeted for polio immunization must be far larger than that for smallpox. And, whereas people needed to be vaccinated against smallpox only once for immediate protection, a single dose of polio vaccine does not always take--children with diarrheal illnesses tend to pass the vaccine straight through--and so a repeat round of immunization is required within four to six weeks. In logistical terms, it's the difference between extinguishing a candle flame and ...