What is polio?

Polio (full name: poliomyelitis) is an infectious disease caused by the poliovirus. It is transmitted through contact with an infected person primarily through the fecal-oral route. The virus enters the body through the mouth or respiratory system and multiplies in the throat and intestines. It can travel through the blood and may enter the central nervous system (spinal cord and brain), causing muscle weakness, paralysis, and in some cases, even death. The virus exits the body through the feces (stool).

The term “polio” refers to the paralytic form of the disease. Only those with this condition are said to have polio. Polio is fatal in 2-10% of cases for those who have the paralytic form because the muscles that are required for breathing cannot function normally.

Post-polio syndrome can occur from 15 to 40 years after the initial infection. Up to 40% of patients who survive paralytic polio may develop post-polio syndrome in the future. They might experience muscle pain, weakness or even paralysis many years after their original illness.

What causes polio?

Polio is caused by the poliovirus. The virus enters the body through the mouth. It is spread through contact with the feces (stool) of an infected person or through exposure to phlegm or mucus when an infected person coughs or sneezes. Polio can also be transmitted by handling objects that are contaminated with fecal matter containing the virus and then putting your hands in your mouth. Poor hygiene or unsanitary conditions leading to contamination of food or water supplies with the virus have also been linked to polio outbreaks.

A person who is infected with the virus can remain contagious for 1 or 2 weeks after symptoms first appear. An infected person can carry the virus and infect others even if he or she does not appear to be sick.

Although people of any age can get polio, children age 5 or younger are at greater risk of infection.

What are the symptoms of polio?

Most people (about 72%) who are infected with the poliovirus will not show any apparent symptoms.

Another 25% of those infected will experience symptoms that are similar to those of the flu, including:

These symptoms usually last for 2 to 5 days, and then disappear.

However, a smaller number of people develop more severe symptoms that are due to involvement of the spinal cord and brain.

These symptoms include:

  • Paresthesia: Feeling of pins and needles in the legs or arms.
  • Meningitis: Infection of the coverings around the brain and spinal cord.
  • Paralysis: Absent or reduced ability to move the legs, arms, and/ or breathing muscles.

About 1 in 200 people who are infected with the poliovirus will experience paralysis, which may result in permanent damage or death.

Last reviewed by a Cleveland Clinic medical professional on 12/07/2014.


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