Today, India celebrated a long-sought milestone in its fight against polio: By all indications, the country has gone 1 year without a single case. (Final confirmation is expected in a few weeks, when the most recent laboratory samples have been analyzed.) The last known case, in a 2-year-old girl in West Bengal, occurred on 13 January 2011. India has been one of four so-called endemic countries in which public health efforts were never able to interrupt indigenous transmission of the wild poliovirus. Because of its sweeping poverty, population density, and poor sanitation, India has proved a particularly tough environment in which to wipe out the virus, with the country delivering an estimated 1 billon doses of polio vaccine each year. For years, India recorded more cases annually than any other country. But thanks to redoubled efforts by the government, the partners in the Global Polio Eradication Initiative (GPEI), and a recent infusion of money and energy from the Bill and Melinda Gates Foundation, cases dropped from 741in 2009 to zero. India’s achievement is a major boost to the beleaguered GPEI, which has spent more than $8 billion over the past 23 years to rid the world of the disease—a goal originally set for 2000. Still, the program fell short of meeting its goal of stopping poliovirus transmission in two endemic countries by the end of 2011. 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The GPEI’s influential Independent Monitoring Board noted in its October report that “GPEI is not on track to interrupt polio transmission by the end of 2012 as it planned to.” Worldwide, more than 600 polio cases were reported in 2011, and cases are surging in a number of countries — not just the three other endemic countries of Pakistan, Afghanistan, and Nigeria, but in a dozen reinfected countries, many in Africa. Public health experts say the alarming rise in polio cases in neighboring Pakistan—192 in 2011—poses a huge threat to India’s fragile success. (Many countries have been declared polio-free only to be reinfected by virus imported from another country.) While applauding India’s achievement, Hamid Jafari, manager of the National Polio Surveillance Project, a collaboration between the World Health Organization and the Government of India, warns that “risks and challenges remain and final success requires maintenance of highly sensitive surveillance for poliovirus, intense ongoing immunization against polio, and a heightened state of emergency preparedness to respond to any circulating poliovirus.” India plans to vaccinate 174 million children against polio in the next 3 months.