Medical Definition of polio
: an infectious disease especially of young children that is caused by the poliovirus ◆Individuals infected with the poliovirus are often asymptomatic. In approximately 25% of cases, polio presents as a mild to moderate illness marked by headache, fever, sore throat, vomiting, diarrhea, and fatigue. Polio affects the central nervous system only infrequently with inflammation and sometimes destruction of the motor neurons in the gray matter of the spinal cord and brain stem. Central nervous system involvement results in temporary or permanent muscle weakness or flaccid paralysis of muscles especially of the limbs and typically the legs. Polio may become life-threatening when paralysis affects the muscles involved in breathing and swallowing. <Thanks to the Salk and Sabin vaccines, the specter of crippling polio that once made summers an apprehensive time for Americans has long since passed.—People Weekly, 17 Sept. 1984> <While the last case of naturally occurring polio in the United States was in 1979, the disease remains prevalent in other areas of the world.—Evan Johnson, The Addison County (Vermont) Independent, 21 Aug. 2014>—called also , ; see post-polio syndrome
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