Polio, still lurking in the shadows.

Introduction Iron lungs sucking breath into immobile bodies. Paralysis. Useless limbs. Forced separation of children from their families. Polio conjures up a nightmarish vision, in part due to the rapid and unexpected onset of paralysis, the inability to predict who might succumb, and the absence of any cure for the potentially lifelong poliovirus-associated paralysis. Sporadic cases of polio have plagued us for thousands of years. In the last 150 years, epidemics of polio have generated fear and confusion. Ironically, associated with increased sophistication in clean water supplies and sewage disposal in cities, the immunity that had previously been generated from early contact with the virus was delayed until a later stage of development, leading to mass outbreaks of paralytic polio. In 1952 polio caused 3200 deaths, and Ͼ21,000 cases of paralysis in the US alone Rehabilitation centers such as the one shown in the photograph in Figure 1 in 1953 were crowded with young patients. After smallpox, poliovirus (PV) has been on the road to potentially becoming the second major human virus to be eradicated from the planet. Many countries have not seen a case of poliomyelitis in a decade or longer, raising our confidence