Polio's Back. Why Now?

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But low does not mean nonexistent, and the parents of a lot of at-risk kids are doing nothing to reduce the danger. Ninety-two percent of U.S. children ages 19 months to 35 months receive three or more doses of polio vaccine, but those numbers aren't distributed evenly. Up to 2.1 million children in that age group may be either undervaccinated or entirely unvaccinated each year. Many come from poor or uninsured families with no access to health care or health information. Others are on the opposite end of the demographic arc--well-educated and comparatively wealthy Americans who opt out of vaccinations for their children either because they are suspicious of vaccines in general or because their religious beliefs forbid them. Home-schooled kids may be at particular risk, since their parents can sidestep the rules requiring vaccinations for all children in the public school system.

Kids left unprotected become part of a dangerous underbrush that can burn fast when a virus hits. The last polio outbreak in the U.S., in 1979, struck a vaccine-averse Amish community, paralyzing 14 people. That virus originated outside the country. "There are people in the U.S. who question vaccinations," says Heidi Larson of UNICEF. "But I think it's because they don't see the impact of the disease around them."

That's not a problem in the countries now struggling with outbreaks of polio and others that lie in the path of the virus. Polio could yet be snuffed out around the world, like smallpox, which was officially declared eradicated in 1980. But it will take more work in the developing world--and less complacency in the developed one--before that happens. --Reported by Helena Bachmann/Geneva, Sora Song/New York and Jason Tedjasukmana/Cidadap