Poliomyelitis (polio) is a highly infectious
viral disease that can involve the nervous system and can cause paralysis.
Polio is most common in infants and children but can occur in adults. Because
of widespread polio vaccination, the disease is now very rare in developed
countries but still occurs in developing countries where vaccination coverage
is not complete. The October 13, 2004, issue of JAMA includes an article about
changing recommendations for giving the polio vaccine in the United States.
The poliovirus usually enters the body through the mouth from
hands that have contacted the virus from an infected person.
The virus can be found in the throat and multiplies in the intestines.
The poliovirus can invade nerve cells that control muscles, including
those involved with breathing.
Most people infected with the poliovirus have few, if any, symptoms.
Others have short-term symptoms that include headache, tiredness,
fever, stiff neck and back, and muscle pain.
If the nervous system becomes infected, permanent paralysis can
occur, usually of the legs and less commonly involving the breathing muscles,
which may require artificial ventilation.
Although there is no cure for polio, it can be prevented by giving the
polio vaccine multiple times, ideally during childhood. There are 2 types
of polio vaccine:
Oral polio vaccine (OPV) is taken by
mouth and contains weakened but live polio virus.
Inactivated polio vaccine (IPV) contains
killed poliovirus and is given as an injection.
Oral polio vaccine can rarely cause polio and is no longer available
in the United States. Inactivated polio vaccine is thought not to be as good
as OPV in preventing the spread of polio in a community. However, a person
cannot get polio from IPV.
Before polio vaccine became available in the 1950s, thousands of cases
occurred every year in the United States. The last case of polio originating
in the United States (except for cases caused by OPV) was in 1979. To eliminate
cases of polio acquired through OPV, the US national vaccination recommendations
changed in 2000 to use exclusively IPV for vaccination against polio.
In 1988, a global initiative was launched to eradicate polio. Since
the initiative was launched, the number of polio cases has dropped by more
than 99%, from an estimated 350 000 cases worldwide in 1988 to 1919 cases
in 2002. In the same period, the number of countries with significant numbers
of polio cases dropped from 125 to 7. Countries that presently have the highest
rates of polio include Afghanistan, Egypt, India, Niger, Nigeria, and Pakistan.
American Academy of Pediatrics 202/347-8600 http://www.aap.org
Centers for Disease Control and Preventionhttp://www.cdc.gov/nip/menus/vaccines.htm#polio
World Health Organization 202/974-3000 http://www.who.int/en/
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Sources: American Academy of Pediatrics, Centers for Disease Control
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Parmet S, Glass TJ, Glass RM. Polio. JAMA. 2004;292(14):1780. doi:10.1001/jama.292.14.1780