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Alternate Names

  • acute paralytic poliomyelitis or APP
  • polio
  • type 1 poliovirus
  • paralytic poliomyelitis
  • nonparalytic poliomyelitis
  • infantile paralysis


Poliomyelitis (polio) is a viral disease that causes a range of symptoms from a mild, flu-like illness to arm and leg paralysis or even death. A vaccine to prevent polio was developed in the 1950s, and since then the infection has been eliminated from most of the world.

What is going on in the body?

The polio virus is transmitted by the fecal-oral route (e.g. oral ingestion of fecal particles). The virus reproduces in the digestive system and spreads through the blood to the rest of the body. In some individuals, the virus infects nerve cells in the spinal cord causing paralysis of the muscles that they innervate. If the muscles necessary for respiration are affected, then death may ensue if artificial ventilation is not utilized.


What are the causes and risks of the infection?

Polio is caused by the poliovirus. In world areas where poliovirus still circulates, polio can be spread through infected feces or through airborne particles.


What can be done to prevent the infection?

As of January 2007, four countries (Nigeria, India, Afghanistan, and Pakistan) still had ongoing (endemic) transmission of poliovirus, and five other surrounding nations were battling importations of the virus. In each of these countries, children are given oral poliovaccine in "waves" on national or subnational immunization days several times each year.
In addition, so long as polio still exists in the world, routine immunization of children must be maintained. In the United States and in many other countries, inactivated (injectable) polio vaccine is used, eliminating the tiny risk of a vaccine-related polio case which can result from oral (live) polio vaccine. Those traveling to countries that still have polio must be sure to update their immunizations.


How is the infection diagnosed?

Polio may be suspected in a child who has paralysis on one side of the body that occurred after a short, flu-like illness. To diagnose the disease, a spinal tap is done to obtain a sample of cerebrospinal fluid. A throat culture is done, and the person's stool is tested to see if the poliovirus is present. If found, the poliovirus can be characterized in the laboratory to determine its likely source.

Long Term Effects

What are the long-term effects of the infection?

The long-term effects range from none to death, paralysis, and post-polio syndrome. In the past, when the muscles of the lungs were affected, polio almost always led to death. Nowadays less than 5% of persons with polio will die because the respiratory problems can be managed better. Only 1% to 2% of persons infected with polio get symptoms related to nerve damage.
Fortunately, the majority of people infected with polio suffer from no symptoms or a minor flu-like illness. After some years, those with a history of paralysis may again experience deterioration in strength. This phenomenon is known as post-polio syndrome. The cause is not clearly understood; however, some have speculated that the loss of strength is the result of loss of nerve function as happens in normal aging superimposed on the nerve damage resulting from polio.

Other Risks

What are the risks to others?

Polio is very contagious. The virus is spread directly from the stool of an infected person to the mouth of a noninfected person. This is usually from contaminated hands or eating utensils.


What are the treatments for the infection?

People with mild symptoms usually get better after several days of bed rest. In cases of paralysis, physical therapy can help prevent muscle damage while the disease is active. Once the acute illness has ceased, physical therapy can help keep the muscles functioning.
People who have paralysis may experience the following:
  • Muscle spasms and pain that can be treated with medication and hot, moist packs.
  • bladder dysfunction requiring a urinary catheter
  • breathing difficulties requiring a ventilator, or artificial breathing machine

Side Effects

What are the side effects of the treatments?

All medications have side effects. Antibiotics and pain medications have some side effects, such as stomach upset or allergic reactions. Treatments to help with breathing or urination may cause infections.

After Treatment

What happens after treatment for the infection?

After the poliovirus is treated, the person will still need physical therapy to gain strength and mobility. After many years, new nerve cells can begin to fail, resulting in muscle weakness. This is known as postpolio syndrome.


How is the infection monitored?

In the acute setting, monitoring is ongoing. Following the acute illness, physical therapy is the mainstay of treatment for those with residual weakness or paralysis.


Polio, March of Dimes Birth Defects Foundation, 1995

Frequently Asked Questions about Poliomyelitis and Polio Vaccine, Centers for Disease Control, Atlanta, Georgia

Poliomyelitis-United States and Canada, MMWR, March 3, 1999/48 [LMRK];61-66

The MERCK Manual, Of Diagnosis and Therapy, Merck Sharp&Dohme Research Laboratories, Rahway, N.J.

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