Poliomyelitis and the role of risk analysis in global infectious disease policy and management.

In 1988, when the World Health Assembly committed to globally eradicate wild polioviruses by the year 2000, no comprehensive models existed to support rigorous policy analyses that could project the human or financial resources that would be required. However, clear demonstration of an effective strategy for polio eradication by the Pan American Health Organization (PAHO) led world health leaders to anticipate significant reductions in the burden of disease, resulting in large long-term global health and financial benefits. The Global Polio Eradication Initiative (GPEI) has made remarkable progress, reducing the annual number of cases of paralytic polio from an estimated 350,000 (with wild polioviruses endemic in 125 countries in 1988) to fewer than 2,000 cases per year (with endemic circulation remaining in only Afghanistan, Nigeria, Pakistan, and India as of publication of this issue). Challenges in these remaining endemic areas differ, with vaccine campaigns in India missing children (particularly in the minority population), those in Nigeria suffering from operational and political issues, and those in Afghanistan and Pakistan limited by security issues associated with current conflicts. During the past several years, the challenges to successfully eradicating wild polioviruses and our knowledge of them increased as new risks emerged. Notably, as some polio-free countries reduced or eliminated their use of live oral poliovirus vaccine (OPV), local outbreaks occurred due to neurovirulent cir-