Polio

Polio virus. PD image, from http://www.epa.gov

Poliomyelitis ("polio") is a viral paralytic disease. The causative agent, a virus called poliovirus, enters the body orally, infecting the intestinal lining. It may proceed to the blood stream and into the central nervous system causing paralysis and muscle weakness. There are effective vaccines against polio, and since their introduction, the disease has been wiped out in the Americas. The World Health Organization is working to eliminate polio worldwide.

People who have survived polio sometimes develop additional symptoms, notably muscle weakness, decades later; these symptoms are called post-polio syndrome.