Poliomyelitis

Alternative names:

infantile paralysis; polio

Definition:

A disorder caused by a viral infection (poliovirus) that affects the whole body including muscles and nerves. Severe cases may cause permanent paralysis or death.

Causes, incidence, and risk factors:

Poliomyelitis 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 ranges from 5 to 35 days (average 7 to 14 days).

Risks include: lack of immunization against polio; travel to an area that has experienced a polio outbreak; pregnancy; very old or very young age; trauma to the mouth/nose/throat, such as recent tonsillectomy or dental surgery; and unusual stress or physical exertion after an exposure to poliovirus (emotional and physical stress can weaken the immune system).

Polio occurs worldwide; however, cases of polio in the U.S. have not been reported in recent years (only 6 cases were reported in 1991). 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 nonimmunized groups.