What is polio?

Short Answer

Polio is an incurable infectious disease caused by a virus that lives in the throat and intestines. It is spread through contact with the stool, saliva, or mucus of an infected person. For most people infected with the polio virus, complications and symptoms are minor or nonexistent. However, some cases cause paralysis, which can lead to permanent disability and death. While polio isn’t present in the U.S., it is still found in several other countries around the world. There are two types of vaccines – only one of which is used in the U.S. – that are 99% effective in preventing polio.




Symptoms & Incubation

Most people who get infected with poliovirus do not have any symptoms. A small number of people (four to eight people out of 100) will have flu-like symptoms. These symptoms usually last two to five days, then go away on their own. The most serious symptoms can also include weakened or paralyzed limbs; these symptoms cannot be reversed.

An infected person may spread the virus to others immediately before and usually one to two weeks after developing symptoms. The virus may live in an infected person’s feces for many weeks. It can contaminate food and water when people do not wash their hands.



The risk of lifelong paralysis is very serious; about one out of 100 people will have weakness or paralysis in their arms, legs, or both. This paralysis or weakness can last a lifetime. Even children who seem to recover fully can develop new muscle pain, weakness, or paralysis as adults, 30 or 40 years later.

About two to five children out of 100 who have paralysis from polio die because the virus affects the muscles that help them breathe.



Poliovirus is very contagious. The virus lives in an infected person’s throat and intestines. It spreads through contact with the feces (stool) of an infected person and through droplets from a sneeze or cough. Polio can spread if an infected person’s feces contaminates objects (like a door or faucet after someone uses the bathroom and doesn’t properly wash their hands, for example), and then you handle those objects and then touch your mouth.


High-risk Populations

Unvaccinated children who come in contact with people who have recently traveled to areas of the world where polio is still common are more at risk of developing the disease.



The inactivated polio vaccine (IPV), which is the version available in the U.S., is extremely effective in preventing polio.


Safety & Side Effects

IPV is very safe and effective at preventing polio. Vac­cines, like any medicine, can cause allergic reactions. Side effects from IPV are very rare.



Children should get four doses of IPV at the following ages for best protection:

  • First dose at 2 months
  • Second dose at 4 months
  • Third dose at 6 through 18 months
  • Fourth (booster) dose at 4 through 6 years of age

It is safe to get IPV at the same time as other vaccines.


Since the Vaccine Was Introduced…

Before the polio vaccine, more than 20,000 people were paralyzed from polio in the United States each year. Today, thanks to the vaccine, there is no more polio in the United States. But if people stopped vaccinating, it’s possible that we would see cases of polio again. Even though no polio cases have originated in the United States in over 30 years, the disease is still in other parts of the world. It would only take one traveler with polio from another country to bring the disease back to the United States.