What is polio?
Polio (poliomyelitis) is a disease caused by poliovirus. It causes mild or no symptoms in most people, but in some people it can cause paralysis or death.
There are three variations of poliovirus, called wild poliovirus type 1, 2 and 3 (WPV1, WPV2 and WPV3). Wild polio types 2 and 3 have been eradicated (no longer exist), and wild polio type 1 only exists in a few parts of the world. Polio type 1 is most likely to cause paralysis.
Is polio a virus or disease?
Polio is the name of the disease caused by poliovirus.
Is polio still alive today?
Yes, there are still cases of polio in some parts of the world today. While the number of people affected has been greatly reduced, international efforts to eradicate polio are still ongoing.
What are the types of polio?
Polio can affect your body differently depending on where the virus multiplies and attacks. Types of polio include:
- Abortive poliomyelitis causes flu-like and intestinal symptoms. It only lasts a few days and doesn’t cause long-lasting issues.
- Non-paralytic poliomyelitis may cause aseptic meningitis, a swelling of the area around your brain. It causes more symptoms than abortive poliomyelitis and may require you to stay in the hospital.
- Paralytic poliomyelitis happens when poliovirus attacks your brain and spinal cord. It can paralyze the muscles that allow you to breathe, speak, swallow and move your limbs. Depending on what parts of your body are affected, it’s called spinal polio or bulbar polio. Spinal and bulbar polio can appear together (bulbospinal polio). Less than 1% of people with polio get paralytic poliomyelitis.
- Polioencephalitis is a rare type of polio that mostly affects infants. It causes brain swelling.
- Post-polio syndrome is when symptoms of polio come back years after a polio infection.
How does polio affect my body?
Poliovirus gets into your body through your mouth or nose. It makes more copies of itself (reproduces) in your throat and gut (intestines). In some cases, it gets into your brain and spinal cord and causes paralysis. Paralysis can affect your arms, legs or the muscles that control your breathing.
Who is at risk for polio?
You’re most at risk for polio if you aren’t vaccinated and you:
- Live in or travel to an area where polio hasn’t been eliminated.
- Live in or travel to an area with poor sanitation.
- Are under 5.
- Are pregnant.
Can adults get polio?
Yes, adults can get polio. Many adults have immunity, either because they’re vaccinated or they’ve had polio. Adults who aren’t vaccinated can get polio if they’re exposed to poliovirus.
How common is polio?
Symptomatic polio is rare in many parts of the world, thanks to worldwide vaccination programs. In most countries, polio is considered eliminated — it’s no longer spread in that area. But when people stop getting vaccinated, polio can start to spread again.
Is polio eradicated?
Wild poliovirus types 2 and 3 are globally eradicated. That means there aren’t any naturally occurring cases anymore. Poliovirus type 1 has been eliminated in most countries but not eradicated worldwide. “Eliminated” means a disease is no longer spread in that area. There can still sometimes be cases and outbreaks, usually from international travel.
Pakistan and Afghanistan are the only countries that still have naturally occurring cases of polio.
When was the last recorded case of polio in the U.S.?
The last case of naturally occurring (wild) polio in the U.S. was in 1979. Cases since then have either been contracted outside of the U.S. or have been from the live polio vaccine (vaccine-derived), which is no longer given in the U.S. The last case of vaccine-derived polio in the U.S. was reported in 2022.
Symptoms and Causes
What are the symptoms of polio?
Between 70% and 95% of people infected with poliovirus don’t have symptoms. Of those with symptoms, most people have the mildest form (abortive poliomyelitis) with flu-like and intestinal symptoms. Paralytic polio causes the most serious symptoms, including paralysis.
Symptoms of abortive poliomyelitis
Abortive poliomyelitis symptoms are similar to many other illnesses. They start three to seven days after getting infected and last a few days. Symptoms of abortive poliomyelitis include:
- Diarrhea or constipation.
- Sore throat.
Symptoms of non-paralytic poliomyelitis
Non-paralytic poliomyelitis starts with the same symptoms as abortive poliomyelitis. Additional symptoms start within a few days, including:
- Neck stiffness.
- Pain or pins-and-needles feeling in your arms and legs.
- Severe headache.
- Sensitivity to light (photophobia).
Symptoms of paralytic poliomyelitis
Paralytic poliomyelitis starts out with symptoms similar to abortive poliomyelitis or non-paralytic poliomyelitis. Additional symptoms can appear days or weeks later, including:
- Sensitivity to touch.
- Muscle spasms.
- Spinal poliomyelitis makes it so you can’t move your arms or legs or both (paralysis).
- Bulbar poliomyelitis makes it hard to breathe, swallow and speak.
- Bulbospinal poliomyelitis has symptoms of both spinal and bulbar polio.
Symptoms of polioencephalitis
You can have symptoms of polioencephalitis on their own or along with flu-like symptoms. Symptoms include:
- Extreme tiredness (fatigue).
- Trouble focusing.
What causes polio?
Polio is caused by a virus (poliovirus). Poliovirus infects your throat and intestines, causing flu-like symptoms. It can then spread to your brain and spine, causing paralysis.
How does polio spread?
Polio spreads through coughing or sneezing or from coming in contact with poop (feces) of an infected person (fecal-oral route). It can spread by:
- Not washing your hands after going to the bathroom or touching poop (like changing diapers).
- Drinking contaminated water or getting it in your mouth.
- Eating foods that have touched contaminated water.
- Swimming in contaminated water. Water can become contaminated when someone who has diarrhea swims in it.
- Coughing or sneezing.
- Being in close contact with someone with polio.
- Touching contaminated surfaces.
Is polio contagious?
Yes, polio is highly contagious. It spreads easily from person to person.
Diagnosis and Tests
How is polio diagnosed?
A healthcare provider diagnoses polio by performing a physical exam, testing samples of body fluids and asking you about your symptoms. It’s important to let your provider know if you’ve traveled anywhere recently.
Your provider might take samples of body fluids to look for signs of polio or other infections, including:
- Spit (saliva) from your throat.
- Poop (stool).
- Cerebrospinal fluid (liquid around your brain and spinal cord).
Because polio symptoms look a lot like flu symptoms, your provider may do other tests to rule out more common conditions.
Management and Treatment
How is polio treated?
There are no specific medications to treat polio. If you have paralytic polio, you’ll receive physical therapy. If your breathing muscles are weakened or paralyzed, you’ll need mechanical ventilation, a machine that helps you breathe.
You might be able to improve your symptoms by:
- Drinking fluids (such as water, juice and broth).
- Using heat packs to help muscle aches.
- Taking pain relievers, such as ibuprofen (Advil®, Motrin®).
- Doing physical therapy and any exercise recommended by your healthcare provider.
- Getting plenty of rest.
Is there a cure for polio?
No, there’s no cure for polio. There isn’t any way to make it go away faster or prevent paralysis.
How can I prevent polio?
The best way to prevent polio is to get vaccinated. Vaccination is usually done in childhood. If you didn’t get vaccinated as a child or don’t know if you did, ask your healthcare provider if you should get vaccinated.
Recommended polio vaccination schedule
Healthcare officials recommend four polio shots in childhood:
- First shot at 2 months old.
- Second shot at 4 months old.
- Third shot between 6 and 18 months old.
- Booster shot between 4 and 6 years old.
If you’ve never been vaccinated for polio and it’s recommended you get vaccinated as an adult, you’ll get three shots:
- Two doses one to two months apart.
- A third dose six to 12 months after the second.
Adults at higher risk for polio
Your healthcare provider might recommend you get a booster dose of polio vaccine (or get vaccinated as an adult, if you’ve never been vaccinated) if you:
- Are planning to travel to certain areas of the world where polio still exists.
- Work in a lab where you might come into contact with poliovirus.
- Work with patients who may be exposed to poliovirus.
What are the types of polio vaccine?
There are two types of polio vaccines: live-attenuated (oral) and inactive. The inactive vaccine is used in most parts of the world, including the Americas and Europe. The live vaccine is only used in parts of the world where polio still occurs naturally.
Inactivated polio vaccine
The inactive polio vaccine (IPV) contains poliovirus that’s been treated (“killed”), so it can’t multiply anymore. It has an inactive version of polio types 1, 2 and 3. IPV is given as a series of shots (injections). You can’t get sick from an inactive vaccine or spread polio to others after getting it.
Oral polio vaccine (live-attenuated)
Oral polio vaccines (OPV) use a live virus that’s been weakened (attenuated), so it shouldn’t make you sick. OPV can contain one, two or all three types of polio virus (monovalent, bivalent or trivalent vaccines). You get the vaccine in a liquid that you swallow.
OPV creates an immune response in your intestines (mucosal immunity), where poliovirus multiplies, so it can provide better protection than a shot. It also ends up in your poop (stool), so vaccine protection can spread to people you’re in close contact with, even if they’re not vaccinated.
Even though it’s weakened, there’s a small risk (1 in 2.5 million) of getting sick from OPV. Rarely, OPV can change (mutate) and spread from person to person like naturally occurring polio (vaccine-derived poliovirus). This can only happen in areas where not many people are vaccinated.
OPV isn’t used in areas where polio is eliminated, which reduces the risk of getting sick from a vaccine. The oral poliovirus vaccine hasn’t been used in the U.S. since 2000.
What is vaccine-derived polio?
Circulating vaccine-derived poliovirus (cVDPV) is a version of poliovirus that was originally part of the oral poliovirus vaccine. Over time, the virus can change (mutate) from the weakened version and spread to people who aren’t vaccinated.
Even though it comes from a weakened version of the virus, the changes make the virus act like naturally occurring polio. Vaccine-derived polio can make you sick. The most common cVDPV is from poliovirus type 2.
When a virus has been eliminated in an area, live vaccines are no longer used. This eventually stops the risk of getting sick from a vaccine-derived virus and should cause cVDPV to disappear over time. Scientists are developing live vaccines that are less likely to change and spread, like nOPV2.
Vaccine-derived polioviruses can only spread where not many people are vaccinated. The polio vaccines significantly reduce — but don’t completely eliminate — your risk of infection. They do reduce the risk that you’ll develop a severe illness or death from a breakthrough case of cVDPV. If you aren’t vaccinated and travel to a country where oral polio vaccine is used, you could get cVDPV.
If you’re immune to one type of poliovirus, can you still get polio?
Yes, if you’re immune to one type of poliovirus, you’re only protected from that type. You can still get polio from one of the other two versions of the virus.
Outlook / Prognosis
What can I expect if I have polio?
Most cases of polio last a few days to a week, but there’s no way of knowing who will progress to paralytic polio and who won’t. You might feel better and then get additional symptoms days or weeks later.
If you had polio as a child, you can develop post-polio syndrome as an adult.
Outlook for polio
While there’s no cure for polio, most people recover without long-lasting damage. Muscle weakness or paralysis can be permanent.
Can polio come back?
Yes, polio symptoms can come back years later as post-polio syndrome. About 40% of people who previously had polio will have some symptoms come back.
Post-polio syndrome is when symptoms of polio come back years after you’ve recovered from polio. It can happen 15 to 40 years after you were first sick with polio.
Post-polio syndrome tends to cause symptoms in muscles that were originally affected by polio. Symptoms of post-polio syndrome may start slowly and then get worse. They include:
- Muscle weakness.
- Muscle atrophy (muscles shrinking in size).
- Difficulty breathing or swallowing.
- Curvature of your spine (scoliosis).
- Joint, muscle and bone pain.
Is post-polio syndrome contagious?
Post-polio syndrome isn’t contagious. Only someone who already had polio can get it.
What is the survival rate of polio?
Most people with non-paralytic polio survive. Of those who develop paralytic polio, up to 10% die of complications.
When should I see my healthcare provider?
Contact your healthcare provider if:
- You’ve been exposed to polio and have symptoms, especially if you aren’t vaccinated.
- You have questions about getting vaccinated or getting your child vaccinated.
What questions should I ask my doctor?
- How can I take care of myself at home?
- When should I follow up with you?
- What symptoms should prompt me to go to the hospital?
- Am I contagious? For how long?
- Can I go to work or school?
- What can I do to make sure I don’t infect other people?
- When will I feel better?
- Will I have any long-term problems?
Frequently Asked Questions
What do they call polio today?
Even though we’ve known about it for over a century, the illness that comes from poliovirus is still called “polio” today. You also might hear it called poliomyelitis.
How can we get rid of (eradicate) polio?
The best way to completely get rid of, or eradicate, an illness is through vaccination. When enough people are vaccinated, the virus has no one left to infect, and it will disappear. If people stop getting vaccinated before a disease is completely eradicated, it can come back, even if there are very few cases in the world.
What is the history of polio in the U.S.?
The first recorded polio epidemics started in the late 1800s, but historians think polio existed long before then. Outbreaks of polio in the early 1900s paralyzed and killed thousands of people. In the last outbreak in 1952, polio paralyzed more than 21,000 people in the U.S., most of them children.
Widespread use of polio vaccines starting in 1955 greatly reduced poliovirus infections, with only 62 cases in 1965. The last case of naturally-occurring polio in the U.S. was reported in 1979. Polio was declared eliminated in the U.S. in 1994.
Polio cases are still occasionally reported in the U.S., usually as a result of international travel. Polio could come back in the U.S. if vaccination rates drop too low.
What is an iron lung?
An iron lung is a large machine that uses pressure to get your lungs to breathe. People whose breathing muscles were weakened or paralyzed by polio used them in the early and mid-1900s. Though iron lungs have been replaced by newer breathing therapies, a small number of polio survivors still use them.
A note from Cleveland Clinic
Vaccinations have eliminated polio in many parts of the world, but we’re still working to completely eradicate it. As long as polio still exists in any part of the world, it can come back and cause severe illness in those who aren’t protected by vaccination. The best way to protect yourself and your community is to get vaccinated.
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