Polio is a viral disease that can affect nerves and can lead to partial or full paralysis. The medical name for polio is poliomyelitis.


Polio is a disease caused by infection with the poliovirus. The virus spreads by:

The virus enters through the mouth and nose, multiplies in the throat and intestinal tract, and then is absorbed and spread through the blood and lymph system. The time from being infected with the virus to developing symptoms of disease (incubation) ranges from 5 to 35 days (average 7 to 14 days). Most people do not develop symptoms.

Risks factors include:

As a result of a global vaccination campaign over the past 25 years, polio has largely been eliminated. The disease still exists in some countries in Africa and Asia, with outbreaks occurring in groups of people who have not been vaccinated. For an updated list of these countries, visit the website: www.polioeradication.org.


There are four basic patterns of polio infection: inapparent infection, abortive disease, nonparalytic, and paralytic.


Most people infected with poliovirus have inapparent infections. They usually do not have symptoms. The only way to know if someone has the infection is by performing a blood test or other tests to find the virus in the stool or throat.


People who have abortive disease develop symptoms about 1 to 2 weeks after getting infected with the virus. Symptoms may include:

These symptoms last up to 5 days and people recover completely. They have no signs of nervous system problems.


People who develop this form of polio have signs of abortive polio and their symptoms are more intense. Other symptoms may include:


This form of polio develops in a small percentage of people who are infected with the polio virus. Symptoms include those of abortive and nonparalytic polio. Other symptoms may include:

Exams and Tests

During a physical examination, the health care provider may find:

Tests that may be done include:


The goal of treatment is to control symptoms while the infection runs its course. There is no specific treatment for this viral infection.

People with severe cases may need lifesaving measures, such as help with breathing.

Symptoms are treated based on how severe they are. Treatment may include:

Outlook (Prognosis)

The outlook depends on the form of the disease and the body area affected. Most of the time, complete recovery is likely if the spinal cord and brain are not involved.

Brain or spinal cord involvement is a medical emergency that may result in paralysis or death (usually from respiratory problems).

Disability is more common than death. Infection that is located high in the spinal cord or in the brain increases the risk of breathing problems.

Possible Complications

Health problems that may result from polio include:

Post-polio syndrome is a complication that develops in some people, usually 30 or more years after they are first infected. Muscles that were already weak may get weaker. Weakness may also develop in muscles that were not affected before.

When to Contact a Medical Professional

Call your provider if:


Polio immunization (vaccine) effectively prevents poliomyelitis in most people (immunization is over 90% effective).

Review Date: 8/25/2019
Reviewed By: Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School; Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital, Boston, MA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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