What is Polio?

polio virus
  • Polio, or poliomyelitis, is a disabling and life-threatening disease caused by the poliovirus.
  • The virus spreads from person to person and can infect a person’s spinal cord, causing paralysis (can’t move parts of the body).


Most people who get infected with poliovirus (about 72 out of 100) will not have any visible symptoms.

About 1 out of 4 people (or 25 out of 100) with poliovirus infection will have flu-like symptoms that may include:

  • Sore throat
  • Fever
  • Tiredness
  • Nausea
  • Headache
  • Stomach pain

These symptoms usually last 2 to 5 days, then go away on their own.

A smaller proportion of people (much less than one out of 100, or 1-5 out of 1000) with poliovirus infection will develop other, more serious symptoms that affect the brain and spinal cord:

  • Paresthesia (feeling of pins and needles in the legs)
  • Meningitis (infection of the covering of the spinal cord and/or brain) occurs in about 1 out of 25 people with poliovirus infection
  • Paralysis (can’t move parts of the body) or weakness in the arms, legs, or both, occurs in about 1 out of 200 people with poliovirus infection

Paralysis is the most severe symptom associated with polio, because it can lead to permanent disability and death. Between 2 and 10 out of 100 people who have paralysis from poliovirus infection die, because the virus affects the muscles that help them breathe.

Even children who seem to fully recover can develop new muscle pain, weakness, or paralysis as adults, 15 to 40 years later. This is called post-polio syndrome.

Note that “poliomyelitis” (or “polio” for short) is defined as the paralytic disease. So only people with the paralytic infection are considered to have the disease.

Post-Polio Syndrome (OPHPR)

Polio has been around since ancient times. This ancient Egyptian tomb painting shows a man with a withered leg unable to bear weight without use of a walking stick. This means that most muscle fibers are replaced with scarring (muscle-wasting) that is permanent.

If someone had polio as a child or young adult but had kept or recovered some or all movement of weakened arms or legs, even to the point of being athletic afterward, they can risk becoming weaker in late adulthood. That is post-polio syndrome (PPS), a condition that can affect polio survivors decades after they recover from their initial poliovirus infection. Some PPS patients become wheelchair-bound when they had not been before.

children holding up hands


  • Poliovirus is very contagious and spreads through person-to-person contact.
  • It lives in an infected person’s throat and intestines.

Poliovirus only infects people. It enters the body through the mouth and spreads through:

  • Contact with the feces (poop) of an infected person
  • Droplets from a sneeze or cough of an infected person (less common)

You can get infected with poliovirus if:

  • You have picked-up minute pieces of feces on your hands, and you touch your mouth.
  • You put in your mouth objects like toys that are contaminated with feces.

An infected person may spread the virus to others immediately before and up to 2 weeks after symptoms appear.

  • The virus can live in an infected person’s feces for many weeks. It can contaminate food and water in unsanitary conditions.
  • People who don’t have symptoms can still pass the virus to others and make them sick.

Prevention and Treatment

There are two types of vaccine that can prevent polio:

  • Inactivated poliovirus vaccine (IPV) given as an injection in the leg or arm, depending on the patient’s age. Only IPV has been used in the United States since 2000.
  • Oral poliovirus vaccine (OPV) is still used throughout much of the world.

Polio vaccine protects children by preparing their bodies to fight the poliovirus. Almost all children (99 children to 100 out of 100) who get all the recommended doses of the inactivated polio vaccine will be protected from polio.

Diagnosis, Specimens, & Containment


man holding syringe

CDC laboratories conduct testing for poliovirus including culture, PCR, genome sequencing, and serology.


multipe syringes

CDC guidance on maintaining the integrity of specimens for collection, storage, and shipment.



CDC containment of the poliovirus is critical to minimizing the risk of the virus causing harm in the environment.

Page last reviewed: September 28, 2021
Content source: Global Immunization