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Poliomyelitis
DefinitionPoliomyelitis is a disorder caused by a viral infection (poliovirus) that can affect the whole body, including muscles and nerves. Severe cases may cause permanent paralysis or death. Causes, incidence, and risk factorsPoliomyelitis is a communicable disease caused by infection with the poliovirus. Transmission of the virus occurs by direct person-to-person contact, by contact with infected secretions from the nose or mouth, or by contact with infected feces. The virus enters through the mouth and nose, multiplies in the throat and intestinal tract, and then is absorbed and spread through the blood and lymph system. Incubation (the time from being infected with the virus to developing symtoms of disease) ranges from 5 to 35 days (average 7 to 14 days). Risks include:
Polio occurs worldwide. There have been very few cases in the Western hemisphere. It once affected mostly infants and children, but now is mostly seen in people over 15 years old. It is more common in the summer and fall. Adults and young girls are more likely to be infected, but infection in young boys is more likely to result in paralysis. Between 1840 and the 1950s, polio was a worldwide epidemic. Since the development of polio vaccines, the incidence is much reduced. Outbreaks still occur, usually in non-immunized groups. SymptomsThere are three basic patterns of polio infection: subclinical infections, nonparalytic, and paralytic. Approximately 95% of these are subclinical infections, which may go unnoticed. Clinical poliomyelitis affects the central nervous system (brain and spinal cord) and is divided into nonparalytic and paralytic forms. It may occur after recovery from a subclinical infection. Subclinical Infection
Nonparalytic Poliomyelitis
Paralytic Poliomyelitis
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lack of immunization against polio
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