What Causes Polio?
Polio (also termed poliomyelitis or infantile paralysis) is an infectious disease caused by an enterovirus. The disease is characterized infection of the central nervous system that produces a wide range of symptoms from a mild nonparalytic infection to total paralysis that can happen over a few hours. There are three types or strains of polio virus; type 1 causes about 85% of all paralytic illness due to polio.
The history of polio infecting humans is long. A few Egyptian mummies from about 6000 to 1209 BC have been found with withered and deformed limbs that are probably due to polio. The first known written description of polio was in 1789, and the first described epidemic was described in 1834, although it is likely many outbreaks occurred before this date. Perhaps the most public figure who had polio was the U.S. president, Franklin D. Roosevelt. The viruses that cause polio were finally cultivated in tissue cultures in 1949. Affected individuals who were too weak to breathe were placed in an "iron lung" device that helped them breathe. Dr. Jonas Salk developed the first killed virus vaccine in 1954, and Dr. Sabin developed the live attenuated viral vaccine in 1958 (OPV or oral polio vaccine). In 2000, the U.S. switched to use of IVP shots (inactivated polio vaccine by injection); many other countries still use OPV. Polio vaccine development is a success story. The polio viruses survive in the wild only in humans and are transmitted only through human contact. It has been the goal of agencies like the World Health Organization (WHO) to eradicate polio worldwide. The efforts have led to a 99% decrease in polio infections worldwide with many countries reporting no new infections in years due to widespread vaccination programs. However, a few countries in Africa and the Middle East still see new infections. Developed countries see polio in the elderly or in immigrants. With ongoing vaccine efforts, the WHO still believes that, like smallpox, polio can be eradicated in the near future.
What Are the Risk Factors for Polio?
The greatest risk for polio infection is not being vaccinated against the disease. Other risk factors include people with immunodeficiency (for example, HIV and cancer), very young individuals, pregnant females, people under extreme stress and exposed to polio, polio patient caregivers, lab personnel working with live polio viruses, and travel to areas where polio is still common.
Last Reviewed 11/21/2017
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