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
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?
There are two kinds of polio vaccine: IPV, which is the
shot recommended in the United States today, and a live, oral polio
vaccine (OPV), which is drops that are swallowed. Until recently OPV
was recommended for most children in the United States. OPV helped
us rid the country of polio, and it is still used in many parts of
Both vaccines give immunity to polio, but OPV is better at
keeping the disease from spreading to other people. However, for a
few people (about one in 2.4 million), OPV actually causes polio.
Since the risk of getting polio in the United States is now
extremely low, experts believe that using oral polio vaccine is no
longer worth the slight risk, except in limited circumstances which
your doctor can describe. The polio shot (IPV) does not cause polio
The recommended schedule
for polio vaccination is three doses of IPV at 2 , 4, and 6 months
of age, and a booster at 4-6 years of age. 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.osted 01-17-07