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Polio is caused by a virus that enters the human body through the mouth and produces a mild infection in the small intestine. In a small percentage of cases, the infection spreads to the bloodstream and destroys cells in the central nervous system that are responsible for muscular contraction. The result can be serious illness, paralysis, or death.

Primarily a childhood disease, polio is spread by human-to-human contact and through contaminated food and water. Victims with mild cases can become inadvertent carriers. Though believed to be present in ancient Egypt and ancient Greece, polio was not recognized as a widespread threat to public health prior to cluster outbreaks during the nineteenth century in Europe and the United States. Public recognition in the US intensified after Dr. Charles Caverly documented a mini- epidemic of polio in his hometown of Otter Valley, Vermont, where 123 cases of the disease in 1884 left 50 people paralyzed and 18 dead. During the first half of the twentieth century polio crippled and killed thousands of children in the United States. Despite notable successes against bacterial diseases during that period, this viral affliction continued to baffle the scientific community. Probably because its victims were children, often from comfortable social situations, anti-polio campaigns galvanized one of the most successful fund-raising efforts in US history around mid-century. In the mid-1950s, rival scientists Jonas Salk and Albert Sabin developed vaccines that dramatically and quickly ended polio as a serious disease in nations that could afford to vaccinate their populations.