Polio is a potentially deadly and crippling infectious disease caused by a virus. The virus spreads from person to person and can invade an infected person’s brain and spinal cord, causing paralysis. There is no cure, but it can be prevented with vaccination.
- Transmission and Symptoms
Poliovirus is very contagious and can spread easily from person-to-person. The virus lives in an infected person’s throat and gut. It can enter the body through the mouth from droplets of an infected person when they sneeze or cough. The poliovirus can also spread through contact with the feces (poop) of an infected person and not washing their hands before touching their mouth, eating, cooking or preparing food. One can also get infected if they put objects like toys that are contaminated with feces (poop) of an infected person.
An infected person may spread the virus to others instantly before and about 1 to 2 weeks after symptoms appear. The virus can live in an infected person’s feces for many weeks. It can pollute food and water in unsanitary conditions.
Most people who get infected with poliovirus (around 72 out of 100) will not have any visible signs or symptoms. About 1 out of 4 people with poliovirus infection will have flu-like symptoms including:
- Sore throat
- Stomach pain
These symptoms usually last 2 to 5 days then go away on their own.
A smaller amount of people with poliovirus infection will develop other more serious signs and symptoms that can 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 serious symptom of polio because it can lead to permanent disability and death. Between 2-10 of 100 people who have paralysis from polio, die because the virus infects 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 (www.cdc.gov/polio/us/pps.html).
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.
Polio vaccine protects children by preparing their bodies to fight the polio virus. Almost all children (99 children out of 100) who get all the recommended doses of vaccine will be protected from polio.
There are two types of vaccine that can prevent polio: inactivated poliovirus vaccine (IPV) and oral poliovirus vaccine (OPV). Only IPV has been used in the United States since 2000; OPV is still used throughout much of the world.
Thanks to effective vaccine, the United States has been polio-free since 1979. However, poliovirus is still a serious threat in some countries. Currently, there are four regions of the world (the Americas, Europe, South East Asia and the Western Pacific) that are certified polio free, but in a small number of countries the spread of this disease has never stopped, putting all the countries at risk. Polio has no cure, making vaccination the only way to eradicate it. However, continued conflict, political instability, hard-to-reach populations, and attempts to ban vaccination in some areas continue to pose complex challenges and threaten to derail decades of work.