What Is Polio?

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Poliomyelitis, commonly known as polio, is a contagious disease that primarily affects children under age five (but it can impact a person at any age who has not been vaccinated). The disease is caused by a virus called the poliovirus. Polio is commonly known as a crippling disease that spreads from person to person, causing paralysis (the inability to move) of muscles as a result of the virus invading the brain and spinal column of the host (the person who is infected with a virus).

Paralytic polio symptoms
Verywell / Nusha Ashjaee 

History of Polio

Historically, there was no vaccine to prevent polio. Between the years of 1937 and 1997, over 400,000 Americans are said to have contracted polio. The virus impacts the nervous system, causing partial or full paralysis, and can result in difficulty breathing or even death. This is the reason the infamous “iron lung” was used as a life-saving treatment for those suffering from polio who had trouble breathing.

The 1950s brought a peak in the incidence of polio cases and mass hysteria about contracting the disease—particularly for parents, in fear of their kids contracting the disease. Many people avoided swimming, going to movie theaters, and public places altogether to avoid taking any chances on the disease. People were afraid of having contact with strangers and many feared that even casual contact—such as a handshake—may even cause the disease. Thankfully, the 1950s also brought about the approval of the polio vaccination for use in the public.

In 1955 the vaccine, developed by a man named Jonas Salk, was launched. This was perhaps one of the most important breakthroughs in medical history. Salk was invited by President Eisenhower to visit the White House, as Eisenhower thanked Salk for saving the children of the world from the horrors of Polio, the president became choked up. When the announcement was made publicly, people ran out into the streets, many crying with joy.

Astoundingly, within just two years of the availability of the vaccine, the number of cases of polio in the United States decreased by 85 to 90%.

Polio Symptoms

According to the Centers for Disease Control (CDC) in Atlanta, Georgia, “Most people who get infected with poliovirus (about 72 out of 100) will not have any visible symptoms. About one out of four people with poliovirus infection will have flu-like symptoms.”

These “flu-like” symptoms, also referred to as non-paralytic polio, mimic common flu symptoms and usually last from two to five days. Non-paralytic polio symptoms go away without any type of intervention, they may include:

  • Sore throat
  • Fever
  • Fatigue
  • Stomach discomfort
  • Nausea
  • Headache

Paralytic Polio Symptoms

Of the total number of those infected with the polio virus, a smaller number (than those with mild flu-like symptoms) will develop serious symptoms—such as those involving the nervous system (brain and spinal column). The symptoms, which are considered the most serious may begin mimicking non-paralytic polio (such as fever and headache). Next, there is a progression to more serious symptoms such as:

  • Loss of reflexes
  • Severe muscle aches
  • Flaccid paralysis (floppy limbs)
  • Paresthesia (tingling, "pins and needles" feeling in the legs)
  • Meningitis (infection of the membranes covering the brain and spinal cord), which occurs in one in 25 people with polio according to the CDC
  • Paralysis (inability to move parts of the body) or weakness in the arms and/or legs, which occurs in about one in 200 people with polio, according to the CDC
  • Death (from the paralysis of muscles that are required for breathing)

Paralytic polio can cause long term or permanent paralysis of muscles, disability (such as being unable to walk without crutches), bone deformities, or death.

Post-Polio Syndrome       

Not all of those who completely recover from Polio remain symptom-free. Some of the children go on to develop weakness, muscle pain, or paralysis during adulthood—15 to 40 years later, says the CDC. This is referred to as post-polio syndrome. Symptoms of post-polio syndrome may include:

  • Muscle or joint weakness and pain which progressively worsens
  • Fatigue
  • Atrophy of muscles (wasting)
  • Problems swallowing or breathing
  • Apnea or other sleep-related breathing disorders
  • Inability to tolerate cold temperatures

When to See a Doctor

According to Mayo Clinic, it’s important to see the healthcare provider when:

  • the complete recommended regime of vaccinations has not been given
  • symptoms of an allergic reaction occur
  • a person who had polio in the past is having unexplained symptoms of fatigue and weakness
  • a person who has recently traveled abroad is experienced symptoms like those caused by polio


Polio is a highly contagious disease that is spread from person to person by several methods or modes of transmission. The poliovirus only occurs in humans. Once contracted, the contagious virus resides in the infected person’s intestines and throat. A few days after exposure, it can then spread through person-to-person contact, right before symptoms appear.

When the feces of an infected person is introduced (via the mouth) to another person, the disease is transmitted. This commonly occurs when there is contamination of drinking water or food, called “fecal-oral transmission.”

Another common mode of transmission is called droplet spread. Although this mode is less common than fecal-oral transmission, it does occur as a result of infected droplets from sneezing or coughing. Other ways to transmit the disease include:

  • direct contact (via contaminated stool/feces or droplets spread on the hands, then touching the mouth)
  • oral to oral (mouth to mouth) transmission by way of a person’s infected saliva (like kissing, which may account for some instances of polio)
  • fecal to oral, through the water supply; in areas of poor sanitation, this was historically a common mode of transmission, involving stool/feces from a person infected with polio getting into the water supply
  • through food (contaminated by feces from an infected person)
  • droplet spread (via a sneeze or cough from an infected person)
  • contact with an object (such as a toy) contaminated with an infected person’s stool/feces or saliva/droplet spread, that is put into the mouth
  • the poliovirus can spread to others right before symptoms start, about 3–6 days after exposure. It can live in a person’s feces for several weeks, contaminating water and food in unsanitary conditions

The most dangerous time for polio to be transmitted is before symptoms have occurred because others are unaware that the disease is present.


Polio may be suspected if symptoms are detected during a physical exam, including neck stiffness, abnormal reflexes, and problems swallowing or breathing. The diagnosis is confirmed by a lab evaluation of a sample of throat secretions, cerebrospinal fluid (the clear liquid that surrounds the brain and spinal column), or stool that is positive for poliovirus.


There is no known effective treatment for polio, other than palliative treatment (keeping a person comfortable) and prevention of complications. This is the reason that getting fully vaccinated is so important. Supportive treatment may include:

  • Ventilators (to enable normal breathing)
  • Pain medication
  • Physical therapy (to prevent loss of muscle function)


There are two different types of vaccinations that can prevent polio. The first is called the oral poliovirus vaccine (OPV), which is taken by mouth, and the second is the inactivated poliovirus vaccine (IPV), which is injected into the bloodstream. In the United States, only the IPV form of the vaccine has been used since the year 2000; however, in other parts of the world, the OPV is still used.

According to the CDC, 99 out of 100 children who are fully vaccinated with the oral polio vaccine will be protected against getting polio.

Since the year 1979, there have been no active cases of polio that originated in the United States. However, the virus still occurs in other countries. 

This means that for children, getting fully vaccinated before traveling abroad is imperative (and a booster may be recommended for adults before traveling to areas such as Central and South America, Africa, and Asia).

According to the Mayo Clinic, “Adults who have been vaccinated who plan to travel to an area where polio is occurring should receive a booster dose of inactivated poliovirus vaccine (IPV).” Mayo Clinic adds that after a booster shot, a person will receive a lifetime immunity to the disease.

Complications of the Vaccination

Generally, the polio vaccination is safe, but there are some possible complications that may occur. A common side effect may include pain and redness at the injection site for the IPV vaccine. 

The IPV vaccine has small amounts of antibiotics, including polymyxin B, neomycin, and streptomycin. Anyone who is allergic to these medications should not receive the IPV vaccine.

The IPV can cause more severe symptoms, such as those resulting from a severe allergic reaction—but this is not common. Signs and symptoms of a severe reaction (which could occur within minutes, up to a few hours after vaccination) may include:

  • Hives
  • Dizziness
  • Hoarseness
  • Wheezing
  • Fast heart rate
  • Problems breathing

If any signs of an allergic reaction are observed after an IPV vaccination, it’s vital to seek emergency medical care immediately.

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By Sherry Christiansen
Sherry Christiansen is a medical writer with a healthcare background. She has worked in the hospital setting and collaborated on Alzheimer's research.