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What Is Polio?

Polio (also known as poliomyelitis) is a highly contagious disease caused by a virus that attacks the nervous system. Children younger than 5 years old are more likely to contract the virus than any other group.

According to the World Health Organization (WHO), one in 200 polio infections will result in permanent paralysis. However, the disease has been largely eradicated thanks to the development of a polio vaccine. The most recent WHO poll, in 2010, reported only 1,352 cases of polio worldwide. (WHO)

Thanks to the polio vaccine, the U.S. has not had a reported case of polio since 1979. However, Afghanistan, Pakistan, and Nigeria still have frequent outbreaks.

Types of Polio

There are three types of polio infections:

  • Sub-clinical: Approximately 95 percent of polio cases are sub-clinical, and patients may not experience any symptoms. This form of polio does not affect the central nervous system (the brain and spinal cord).
  • Non-paralytic: This form, which does affect the central nervous system, produces only mild symptoms and does not result in paralysis.
  • Paralytic: This is the rarest and most serious form of polio, which produces full or partial paralysis in the patient. There are three types of paralytic polio: spinal polio (affects the spine), bulbar polio (affects the brainstem), and bulbospinal polio (affects the spine and brainstem).

Post-polio syndrome is a complication that can occur after a person has caught and recovered from poliovirus. Symptoms of the syndrome can appear up to 35 years after the polio infection.

What Causes Polio?

Poliovirus is often transmitted from person-to-person through fecal matter. People living in areas with limited access to running water or flush toilets often get the virus from drinking water contaminated by human waste that contains the virus.

In addition, the virus can be spread by contaminated food or water or direct contact with another infected person. According to the May Clinic, the virus that causes polio is so contagious that anyone living with an infected person will likely become infected themselves. (Mayo Clinic)

Pregnant women, people with weakened immune systems, such as HIV+ people, and young children are the most susceptible to the polio virus. If you have not been vaccinated, you increase your risk of contracting polio by:

  • traveling to an area that has had a recent polio outbreak
  • taking care of or living with someone infected with polio
  • handling a laboratory specimen of the virus
  • having your tonsils removed
  • extreme stress, which can compromise immune system function

Recognizing the Symptoms of Polio

Sub-clinical polio may not trigger noticeable symptoms. In fact it is estimated that 95 to 99 percent of infected patients are asymptomatic. In the five percent of polio cases in which patients do experience symptoms, they can range from mild to severe. Paralytic polio (polio that leads to paralysis) has more severe symptoms and can be fatal. Patients with non-paralytic polio experience mild, flu-like symptoms.

Sub-Clinical Polio

If patients do have symptoms, they usually last for 72 hours or less and may include:

  • headache
  • sore, red throat
  • slight fever
  • vomiting
  • general discomfort

Non-Paralytic Polio

The symptoms of non paralytic polio may last for a couple of days to a week or two and includes

  • fever
  • sore throat in the absence of upper respiratory infection
  • headache
  • vomiting
  • fatigue
  • abnormal reflexes
  • problems swallowing and/or breathing
  • back and neck pain and stiffness, particularly neck stiffness with forward flexion of the neck
  • arm and leg pain or stiffness
  • muscle tenderness and spasms

Paralytic Polio

People with paralytic polio experience the symptoms associated with non-paralytic polio first. Soon after, the following symptoms appear:

  • loss of reflexes
  • severe spasms and muscle pain
  • loose and floppy limbs, sometimes on just one side of the body, this is due to the weakness which results from the involvement of the spine
  • sudden paralysis (temporary or permanent)
  • deformed limbs (especially the hips, ankles, and feet due to prolonged weakenss and the lack of appropriate orthopedic bracing

Full paralysis can eventually develop, but it is rare. Only about one percent of all polio cases will result in a person being permanently paralyzed. Of those patients who experience paralysis, five to 10 percent will die when the paralysis attacks the muscles that control breathing. (CDC)

Post-Polio Syndrome

The symptoms of post-polio syndrome are:

  • continuing muscle and joint weakness
  • muscle pain that gets worse
  • becoming easily exhausted or fatigued
  • muscle wasting, also called muscle atrophy
  • trouble breathing and/or swallowing
  • sleep related breathing problems (sleep apnea)
  • becoming easily cold or
  • new onset of weakness in previously uninvolved muscles

How Do Doctors Diagnose Polio?

Doctors will use the patient’s reported symptoms to help determine whether he or she has polio. During a physical examination, a doctor may notice that the patient has impaired reflexes, back and neck stiffness, or difficulty lifting his or her head while lying flat.

To definitively diagnose polio, a doctor will take a sample of the patient’s throat secretions, stool, or cerebrospinal fluid (fluid surrounding the brain and spinal cord). The sample is then tested to see if it contains poliovirus and if the cells in the cerebrospinal fluid demonstrate changes consistent with what is called aseptic meningitis (a brain infection)

How Do Doctors Treat Polio?

There is no cure for polio. Doctors can only treat the symptoms while the infection runs its course. The most common treatments include:

  • rest
  • painkillers to relieve headaches, muscle aches, and muscle spasms
  • antibiotics for urinary tract infections
  • portable ventilators to help with breathing
  • physical therapy and/or corrective braces to help with walking
  • heating pads or warm towels to ease muscle aches and spasms
  • physical therapy to treat pain in the affected muscles
  • physical therapy to address breathing and pulmonary problems and then pulmonary rehabilitation to increase the patient’s pulmonary endurance as the acute breathing problems improve
  • In advanced cases of leg weakness, when a patient has difficulty walking he or she may need a wheelchair or other mobility device

How to Prevent Polio

The best way to prevent polio is to get vaccinated. Children should get polio shots according to the CDC vaccination schedule, shown below.

Rarely, the shots can cause mild or severe allergic reactions, including:

  • breathing problems
  • high fever
  • dizziness
  • hives
  • swelling of throat
  • rapid heart rate

Adults in the United States are not at a high risk for contracting polio. The greatest risk is when traveling to an area where polio is still common. Make sure to get a series of shots before you travel.

Center for Disease Control Vaccination Schedule



2 months

One dose

4 months

One dose

6 to 18 months

One dose

4 to 6 years

Booster dose

Content licensed from:

Written by: Shannon Johnson
Medically reviewed on: Oct 10, 2016: University of Illinois-Chicago, College of Medicine

This feature is for informational purposes only and should not be used to replace the care and information received from your health care provider. Please consult a health care professional with any health concerns you may have.
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