Here you can download different charts about cases by world region, prevalence rates, and progress towards polio eradication and much more. Polio is an infectious disease that is caused and transmitted by the poliovirus. Most infections do not lead to any symptoms, but—among the unvaccinated—between 1 in 50 and 1 in 500 infections result in paralysis. For some it leads to death. At the start of the 20th century, polio was endemic worldwide, with large epidemic outbreaks every year. But with the development of two vaccines in the 1950s, countries began eliminating polio one by one.