Two years ago, the global campaign to eradicate polio stalled here after rumors spread that the vaccine could cause sterility or AIDS. Teams of vaccinators were taunted and stoned. Parents hid their children. Government officials suspended the program, allowing polio to rebound in northern Nigeria and spread to 17 other countries that had been free of the disease.

That decision continues to spawn outbreaks across Africa and Asia, but in northern Nigeria, the anti-vaccine myths have finally been dispelled. Instead, a series of vaccination campaigns are bringing the disease under control in a region health officials regard as the world's most difficult battleground in the war against polio.

"They've turned this thing around," said R. Bruce Aylward, head of the Global Polio Eradication Initiative, speaking by phone from Geneva. "Real progress is finally being made at that epicenter."

The number of polio cases in Nigeria has fallen by about one-quarter, with 325 confirmed infections so far compared with 453 at the same point in 2004, and the geographical reach of the virus has declined as well, health officials said. Fewer areas in northern Nigeria have reported cases, and the disease has retreated almost entirely from the south, including the sprawling seaside metropolis of Lagos, the country's commercial capital.

The turnaround has come after two years in which Nigeria was the world's leading exporter of the polio virus. Strains genetically related to the outbreak here in 2003 have since been found in 17 countries. So far this year, there have been 1,053 cases reported in 14 countries, topped by Yemen with 415 and followed by Nigeria and Indonesia.

Polio also remains endemic in Niger, Egypt, India, Pakistan and Afghanistan, though the number of cases is on the decline in those countries.

The virus is spread via feces, especially in poor and crowded residential areas, and it can lead to paralysis and death. Vaccines eliminated the disease from the developed world in the 1970s, but in 1988 there were still 350,000 cases in 125 poorer countries. That year, a global eradication campaign was started by the World Health Organization, UNICEF, Rotary International and the U.S. Centers for Disease Control and Prevention.

The effort made significant strides for five years but suffered a serious setback in 2003, when rumors spread throughout northern Nigeria that the polio vaccine contained agents that would sterilize children or cause AIDS. The area is overwhelmingly Muslim, and it was whispered that the vaccine campaign was part of a Western plot to weaken or diminish the Muslim populace.

Tens of thousands of parents refused to allow their children to be vaccinated. Teenage girls hired to deliver the vaccine, a liquid dropped onto the tongue, were harassed. Some political and religious leaders urged a suspension of vaccinations until researchers could assess the truth of the claims, a process that took several months.

In July 2004, vaccinations resumed in Kano, a state surrounding a large urban trading center of the same name. But the number of new infections in Nigeria continued to rise to 782, nearly four times the number from 2002. By the end of 2004, the virus had also spread to at least 12 other African countries that previously had been free of polio.

The Nigerian government has taken a variety of measures to restore trust to the vaccination project. Educational programs have been broadcast on radio and television. President Olusegun Obasanjo personally administered the vaccine to the daughter of Kano's governor. Muslim religious leaders embraced the campaign. New rounds of vaccinations saw progressively higher rates of acceptance.

This month, the latest eradication drive reached more than 90 percent of the estimated 3.8 million children under age 5 in Kano state.

"We still have a residual number of people who are not accepting the vaccine," said Hamisu Walla, the regional polio surveillance officer for the World Health Organization. But he said parents who refuse to allow their children to receive the drops tend to complain about the general lack of health care, rather than express fears of the vaccine itself.

Health officials said they had been surprised by the speed with which polio spread abroad after trouble began in Nigeria -- but also by the ability of coordinated vaccination campaigns to rapidly curb new cases.

Sule Yau Sule, a government spokesman in Kano, said full eradication would come soon as vaccination campaigns reach larger percentages of the region's children.

Aylward, head of the eradication initiative, predicted that stopping polio transmission is possible this year in most of the world, though perhaps not Nigeria.

"It would take a small miracle to get us across the line by the end of 2005 in northern Nigeria," Aylward said. "Everywhere else could still finish."

A girl is vaccinated against polio in Kano, in northern Nigeria, as part of a campaign to administer 40 million doses throughout the country in four days.A child is led through the packed polio ward at Murtala Muhammed Public Hospital in Kano, where local leaders suspended vaccinations two years ago.