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What Is Polio?

Polio (also called poliomyelitis) is a contagious, historically devastating disease. It was virtually eliminated from the Western hemisphere in the second half of the 20th century. Although polio has been around since ancient times, its largest outbreak was in the first half of the 1900s until the polio vaccine was introduced in 1955.

What Are the Signs & Symptoms of Polio?

Polio is a viral illness that in most cases causes no symptoms (called asymptomatic polio). When there are symptoms (symptomatic polio), the illness appears in three forms:

  1. a mild form called abortive polio: Most people with this type may not suspect they have it because their sickness is limited to mild flu-like symptoms such as mild upper respiratory infection, diarrhea, fever, sore throat, and a general feeling of being ill.
  2. a more serious form associated with aseptic meningitis called nonparalytic polio: A few people with this type have symptoms such as sensitivity to light and neck stiffness.
  3. a severe, debilitating form called paralytic polio: This occurs in 0.1%-2% of cases.

People who have abortive polio or nonparalytic polio usually make a full recovery. Paralytic polio, though, causes muscle paralysis and even death.

In paralytic polio, the virus leaves the intestinal tract and enters the bloodstream, attacking the nerves (in abortive or asymptomatic polio, the virus usually doesn't get past the intestinal tract). The virus may affect the nerves controlling the muscles in the limbs and the muscles necessary for breathing, causing respiratory difficulty and paralysis of the arms and legs.


In the United States, it's currently recommended that children have four doses of inactivated polio vaccination (IPV) between the ages of 2 months and 6 years.

By 1964, the oral polio vaccine (OPV) had become the recommended vaccine. OPV allowed large populations to be immunized because it was easy to administer, and it provided "contact" immunization, which means that an unimmunized person who came in contact with a recently immunized child might become immune, too.








During the height of the polio epidemic, the standard treatment involved placing a patient with paralysis of the breathing muscles in an "iron lung" — a large machine that actually pushed and pulled the chest muscles to make them work. The damaged limbs were often kept immobilized because of the confinement of the iron lung. In countries where polio is still a concern, ventilators and some iron lungs are still used.

Historically, home treatment for paralytic polio and abortive polio with neurological symptoms wasn't sufficient. However, asymptomatic and mild cases of abortive polio with no neurological symptoms were usually treated like the flu, with plenty of fluids and bed rest.

The Future of Polio


Reviewed by: Nicole A. Green, MD
Date reviewed: January 2014