STAT | D Sarkar/AP/Getty
Polio is a viral disease that mainly affects children under the age of five. One in 200 cases leads to irreversible paralysis. It’s highly contagious and spreads orally or through tiny, often invisible amounts of feces. Thanks to the rollout of two vaccines for the disease, cases of polio have decreased by 99% since 1988. It’s gone from being endemic in 125 countries to just two.