Polio Home > What Is Polio?
Polio is a viral-based disease that can cause paralysis. Up to 95 percent of people who are infected will not have symptoms. However, even without symptoms, infected people can still spread the virus and cause others to develop the disease. While there is no cure, most people recover from the condition without any long-term problems.
Polio (also known as poliomyelitis or infantile paralysis) is an infectious disease that is caused by a virus. The disease used to be common in the United States. It caused severe illness in thousands of people each year before the vaccine was introduced in 1955.
Polio used to be 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 before the introduction of the Salk vaccine in 1955. The disease peaked in 1952, when there were more than 21,000 reported cases. The number of cases decreased dramatically following the 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 reported cases just five years earlier in 1960.
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. Of the 152 cases, 8 were acquired outside the United States and imported. The remaining 144 cases were vaccine-associated paralytic polio caused by the live oral polio vaccine.
(Click History of Polio for more information.)
Up to 95 percent of people who are infected with poliovirus have no symptoms. However, infected people who do not have symptoms can still spread the virus and cause others to develop the disease.
If a person does develop symptoms, they can be categorized into one of three groups, which include:
- Minor polio symptoms (also known as abortive poliomyelitis)
- Aseptic meningitis
- Paralytic poliomyelitis.
(Click Polio Symptoms for more information or Polio Pictures to see the possible impact of infection.)