Poliomyelitis, often called polio or infantile paralysis, is an acute, viral, infectious disease spread from person to person, primarily via the fecal-oral route. The virus lives in an infected person’s throat and intestines. It is most often spread by contact with the stool of an infected person. You can also get it from droplets if an infected person sneezes or coughs. It can contaminate food and water if people do not wash their hands. Polio is a highly infectious viral disease, which mainly affects young children.
The poliovirus resides only in humans and enters the environment in the feces of someone who’s infected. Poliovirus spreads primarily through the fecal-oral route, especially in areas where sanitation is inadequate.
Poliovirus can be transmitted through contaminated water and food or through direct contact with someone infected with the virus. Polio is so contagious that anyone living with a recently infected person is likely to become infected, too. People carrying the poliovirus can spread the virus for weeks in their feces.
Most people who get infected with poliovirus (about 72 out of 100) will not have any visible symptoms.
About 1 out of 4 people with poliovirus infection will have flu-like symptoms that may include:
- Sore throat
- Stomach pain
These symptoms usually last 2 to 5 days then go away on their own.
A smaller proportion of people 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.
There is no cure for polio, only treatment to alleviate the symptoms. Heat and physical therapy is used to stimulate the muscles and antispasmodic drugs are given to relax the muscles. While this can improve mobility, it cannot reverse permanent polio paralysis.
Polio can be prevented through immunization. Polio vaccine, given multiple times, almost always protects a child for life.
Children should be vaccinated with 4 doses of inactivated polio vaccine (IPV) at the following ages:
- A dose at 2 months
- A dose at 4 months
- A dose at 6-18 months
- A booster dose at 4-6 years
These are the recommended ages, but children traveling to areas where wild poliovirus (WPV) has circulated in the last 12 months should complete the series before international travel. If a child cannot complete the routine series before departure, an accelerated schedule is recommended.
Most adults do not need polio vaccine because they were already vaccinated as children. But three groups of adults are at higher risk and should consider polio vaccination in the following situations:
- You are traveling to polio-endemic or high-risk areas of the world. Ask your healthcare provider for specific information on whether you need to be vaccinated.
- You are working in a laboratory and handling specimens that might contain polioviruses.
- You are a healthcare worker treating patients who could have polio or have close contact with a person who could be infected with poliovirus.
Adults in these three groups who have never been vaccinated against polio should get 3 doses of IPV:
- The first dose at any time,
- The second dose 1 to 2 months later,
- The third dose 6 to 12 months after the second.
Adults in these three groups who have had 1 or 2 doses of polio vaccine in the past should get the remaining 1 or 2 doses. It doesn’t matter how long it has been since the earlier doses.
Adults who are at increased risk of exposure to poliovirus and who have previously completed a routine series of polio vaccine (IPV or OPV) can receive one lifetime booster dose of IPV.