After plaguing humans for thousands of years, polio is on the verge of being wiped out. In 1988, the virus was endemic in 125 countries, but today it exists in only three: Nigeria, Afghanistan and Pakistan. With scientists so close to eradicating polio, their work exhibits a renewed sense of urgency.
Polio, also called poliomyelitis or infantile paralysis, is caused by a virus that can infect nerves and lead to partial or complete paralysis. Between the 1840s and 1950s, polio epidemics occurred worldwide, paralyzing or killing half a million people each year.