Poliomyelitis is a contagious disease caused by infection with the polio virus. The virus enters through the mouth and nose, multiplies in the throat and intestinal tract, and spreads throughout the blood and lymph systems. The virus is transmitted by direct person-to-person contact, through contaminated water and food, by contact with infected fluids from the nose or mouth, or by contact with infected feces. This occurs commonly in areas where sanitation is inadequate. People carrying the polio virus can spread the virus for weeks in their feces, even if they do not experience any symptoms. Polio only affects humans.
Approximately 95% of polio infections are subclinical infections, which may present with flu-like symptoms or no symptoms at all. The other 5% of cases occur when the virus infects the central nervous system, which may cause temporary or permanent muscle paralysis, disability, and deformities of the hips, ankles, and feet. Complications from prolonged immobility may involve the lungs, kidneys, and heart and may be fatal.
Polio has been a health problem throughout recorded history. Between 1840 and the 1950s, polio was a worldwide epidemic, particularly in Europe, North America, Australia, and New Zealand. In 1952, the worst polio epidemic that occurred in the United States affected approximately 58,000 people, mostly children. Children that survived were often paralyzed. According to the World Health Organization (WHO), there are now 10-20 million polio survivors worldwide.
The polio vaccine was developed in the 1950s. In the United States, the last case of naturally occurring polio happened in 1979. Organizations including the WHO, the United Nations Children's Fund (UNICEF), and Rotary International are involved in massive vaccination campaigns to eliminate the polio virus. These efforts have reduced the number of annual diagnosed cases by 99%, from 350,000 cases in 1988 to 483 cases In 2001.
Today, most people in developed countries are immunized against the polio virus and are not exposed to the disease. Persons that are not immunized, have weak immune systems, and travel to places where polio outbreaks are common are at risk for developing polio.
There is no cure for polio. The goal of treatment is to control symptoms and prevent complications. Some forms of polio do not require treatment; however, severe forms may require orthopedic surgery. Common treatments include physical therapy, braces, and corrective shoes.
The most effective way to prevent polio infection is vaccination. The polio vaccine is over 90% effective in providing immunity to the polio virus. Most children in developed countries are routinely vaccinated. However, outbreaks still occur in the developed world, usually in groups of people who have not been vaccinated.
Abortive poliomyelitis, bulbar polio, bulbospinal polio, Heine-Medin disease, infantile paralysis, nonparalytic poliomyelitis, paralytic poliomyelitis, poliomyelitis, poliovirus, post-polio syndrome, spinal polio, subclinical poliomyelitis, vaccination.
types of the disease
Subclinical poliomyelitis, or abortive poliomyelitis, is an illness that does not involve the central nervous system. Patients with this type of polio recover completely. About 95% of polio infections fall into this category.
Poliomyelitis involving the central nervous system
Nonparalytic poliomyelitis: When a polio infection affects the central nervous system, over 99% of polio patients do not suffer paralysis but do experience aseptic meningitis. In these patients, symptoms include headache; neck, back, abdominal, and arm or leg pain; fever; vomiting; weakness; and irritability. After experiencing symptoms for 2-10 days, these patients recover completely.
Paralytic poliomyelitis: Less than one percent of polio cases result in paralysis. In these cases, the muscles become weak and poorly controlled, and finally completely paralyzed (called acute flaccid paralysis). Paralytic polio has several types, based on the part of the body that is affected: the spinal cord (called spinal polio), the brainstem (called bulbar polio), or both (called bulbospinal polio).