In January 2004 health ministers from the countries where polio remains a danger—Afghanistan, Pakistan, Egypt, India, Niger, and Nigeria—pledged to help wipe out the disease by January 2005. But earlier events would sabotage their success: Officials in the densely populated Nigerian state of Kano had suspended immunization in 2003 because of rumors that the vaccine was contaminated. By early November 2004, nearly 800 new cases of the infection had cropped up in Nigeria, and neighboring West African countries that had previously been declared polio-free encountered a resurgence of the disease. “Africa went from the brink of eradication to the largest spread in recent history,” says Bruce Aylward, coordinator of the Global Polio Eradication Initiative for the World Health Organization.
Controlling polio isn’t easy or simple. Infection is virtually impossible to diagnose by sight because only one in 200 people infected will develop the telltale paralysis, and that allows the virus to spread invisibly. In addition, the oral polio vaccine is extremely sensitive to heat, and children must receive as many as 10 doses before they are fully immunized.
The outbreak in West Africa threatens the momentum of the polio eradication campaign, which cut the number of new polio cases worldwide from an estimated 350,000 in 1988 to only 784 in 2003 and wiped out the disease in the Americas, the Western Pacific region, and Europe. But this fall public-health officials mobilized more than 1 million volunteers in 23 countries to combat a polio revival by immunizing more than 80 million children under age 5. Once the last infected countries are declared polio-free, Aylward says, immunization must continue for at least another three years to ensure that the disease has finally been beaten back. Aylward now expects Asia and Egypt to eradicate polio by mid-2005; the rest of Africa could follow within a year. “It’s rare in international development and health that you can work toward such a definite end,” he says.