Polio [PO-lee-oh] is a viral disease that can damage the nervous system and cause paralysis.
The polio virus enters the body through the mouth, usually from hands contaminated with the stool of an infected person.
Polio is preventable by immunization.
Since polio immunization has become widespread in the United States, cases of polio are rare. However, polio remains a problem in many parts of the world.
What is polio?
Polio, short for poliomyelitis, is a disease that can damage the nervous system and cause paralysis. Since polio immunization has become widespread in the United States, cases of polio are rare. However, polio remains a problem in many parts of the world.
What is the infectious agent that causes polio?
Polio is caused by any of three polio viruses.
Where is polio found?
Before the availability of polio immunization, polio was common worldwide. However, with strong immunization programs and efforts to rid the world of polio, circulation of polio viruses is limited to a decreasing number of countries. The greatest risk is now in the Indian subcontinent and, to a lesser extent, in West and Central Africa.
How do people get polio?
The polio virus lives in the throat and intestinal tract of infected persons. The virus enters the body through the mouth, usually from hands contaminated with the stool of an infected person. Objects, such as eating utensils, can also spread the virus. Food and water are not thought to play a major role in the spread of polio.
What are the signs and symptoms of polio?
The polio virus attacks the nerve cells that control muscle movements. Many people infected with the virus have few or no symptoms. Others have short-term symptoms, such as headache, tiredness, fever, stiff neck and back, and muscle pain.
More serious problems happen when the virus invades nerves in the brain and causes paralysis of the muscles used in swallowing and breathing. Invasion of the nerves in the spinal cord can cause paralysis of the arms, legs, or trunk.
How soon after exposure do symptoms appear?
Symptoms usually start 7 to 14 days after exposure to the virus. Infected persons are most contagious from a few days before to a few days after the start of symptoms. However, persons with polio can spread the infection for as long as the virus is in their throat or stool. The virus can be found in the throat for about 1 week after infection and in the stool for 6 weeks or longer.
How is polio diagnosed?
Polio is diagnosed by a blood test or culture.
Who is at risk for polio?
Polio is most common in infants and young children, but complications occur most often in older persons.
What complications can result from polio?
Complications include paralysis, most commonly of the legs. Paralysis of the muscles that control breathing and swallowing can be fatal.
In very rare cases, the oral vaccine used to prevent polio can cause polio paralysis in persons who are vaccinated (1 in every 8.1 million doses) and in people who are close contacts of a vaccinated person (1 in every 5 million doses). About 8 to 9 cases of paralytic polio caused by the oral vaccine have been reported in the United States yearly.
What is the treatment for polio?
There is no treatment for polio. A polio patient must receive expert medical care, especially at the beginning of the illness.
How common is polio?
In the United States, the last case of "wild" polio was in 1979. Wild polio is naturally circulating polio that is not caused by the oral polio vaccine. Except for an occasional importation, all cases of paralytic polio since 1979 have been caused by the oral polio vaccine. However, thousands of polo infections still occur in other parts of the world. Most cases are reported from Asia and Africa.
How can polio be prevented?
Two types of polio vaccine are available: oral polio vaccine (OPV) and inactivated polio vaccine (IPV).
OPV is made with a live but weakened virus. OPV protects vaccinated persons directly. OPV also protects other susceptible persons who are indirectly "vaccinated" as the vaccine virus spreads in the community. Because of wide use of OPV, no cases of paralytic polio caused by naturally circulating polio virus have been reported in the United States since 1979.
IPV is given by injection. It protects vaccinated persons as well as OPV, but it is not believed to be as effective as OPV in preventing the spread of polio virus among non-vaccinated persons. However, IPV is not known to cause polio disease.
As of January 1997, the recommended schedule for polio vaccination for children was two doses of IPV at 2 and 4 months of age, followed by two doses of OPV at 12-18 months and 4-6 years. This schedule is expected to reduce the small number of polio cases caused by the oral vaccine.
Schedules containing all OPV or all IPV can still be used, too. IPV can be given at 2, 4, and 12-18 months, and 4-6 years. OPV can be given at 2, 4, and 6-18 months, and 4-6 years. Parents and doctors can choose among the three schedules.
Booster doses of polio vaccine are also recommended for persons traveling to areas of the world where polio is still a problem.
As is the case with all immunizations, there are important exceptions and special circumstances. Health-care providers should have the most current information on recommendations about polio vaccination.
This fact sheet is for information only and is not meant to be used for self-diagnosis or as a substitute for consultation with a health-care provider. If you have any questions about the disease described above, consult a health-care provider.
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