What are the symptoms of polio?
Up to about 95 percent of people infected with polio have no symptoms. However, infected persons without symptoms can still spread the virus and cause others to develop polio. About four to eight percent of infected persons have minor symptoms such as fever, sore throat, upset stomach, or flu-like symptoms and have no paralysis or other serious symptoms. About one to two percent of infected persons develop aseptic meningitis with stiffness of the back, back or legs, and in some persons increased or abnormal sensations. Symptoms typically last from two to ten days, followed by complete recovery. Less than 1 percent of polio cases result in paralysis of the limbs (usually the legs). Of those cases resulting in paralysis, 5-10% die when the respiratory muscles are paralyzed. The risk of paralysis increases with age.
How common was polio in the United States?
Polio was one of the most dreaded childhood diseases of the 20th Century in the United States. There were usually about 13,000 to 20,000 cases of paralytic polio reported each year in the US before the introduction of Salk inactivated polio vaccine (IPV) in 1955. Polio peaked in 1952 when there were more than 21,000 reported cases. The number of cases of polio decreased dramatically following introduction of the vaccine and the development of a national vaccination program. In 1965, only 61 cases of paralytic polio were reported compared to 2,525 cases reported cases just five years earlier in 1960.
Is polio still a disease seen in the United States?
The last cases of naturally occurring paralytic polio in the United States were in 1979, when an outbreak occurred among the Amish in several Midwestern states. From 1980 through 1999, there were 152 confirmed cases of paralytic polio cases reported. Of the 152 cases, eight cases were acquired outside the United States and imported. The last imported case caused by wild poliovirus into the United States was reported in 1993. The remaining 144 cases were vaccine-associated paralytic polio (VAPP) caused by live oral polio vaccine (OPV).
