Although polio can cause paralysis and death, the vast majority of people who are infected with the poliovirus don't become sick and are never aware they've been infected with polio.
Some people who develop symptoms from the poliovirus contract nonparalytic polio — a type of polio that doesn't lead to paralysis (abortive polio). This usually causes the same mild, flu-like signs and symptoms typical of other viral illnesses.
Signs and symptoms, which generally last one to 10 days, include:
- Sore throat
- Back pain or stiffness
- Neck pain or stiffness
- Pain or stiffness in the arms or legs
- Muscle weakness or tenderness
In rare cases, poliovirus infection leads to paralytic polio, the most serious form of the disease. Paralytic polio has several types, based on the part of your body that's affected — your spinal cord (spinal polio), your brainstem (bulbar polio) or both (bulbospinal polio).
Initial signs and symptoms of paralytic polio, such as fever and headache, often mimic those of nonparalytic polio. Within a week, however, signs and symptoms specific to paralytic polio appear, including:
- Loss of reflexes
- Severe muscle aches or weakness
- Loose and floppy limbs (flaccid paralysis), often worse on one side of the body
Post-polio syndrome is a cluster of disabling signs and symptoms that affect some people several years — an average of 35 years — after they had polio. Common signs and symptoms include:
- Progressive muscle or joint weakness and pain
- General fatigue and exhaustion after minimal activity
- Muscle atrophy
- Breathing or swallowing problems
- Sleep-related breathing disorders, such as sleep apnea
- Decreased tolerance of cold temperatures
- Cognitive problems, such as concentration and memory difficulties
- Depression or mood swings
When to see a doctor
Be sure to check with your doctor for polio vaccination recommendations before traveling to a part of the world where polio may still occur naturally, or where oral polio vaccine (OPV) is still used, such as Central and South America, Africa and Asia. In countries that use the OPV — vaccine made with live, but weakened (attenuated) polio virus — the risk of paralytic polio to travelers is extremely low, but not zero.
Additionally, call your doctor if:
- Your child hasn't completed the series of polio vaccinations
- Your child experiences an allergic reaction after receiving polio vaccine
- Your child has problems other than a mild redness or soreness at the vaccine injection site
- You have questions about adult vaccination or other concerns about polio immunization
- You had polio years ago and are now experiencing unexplained weakness and fatigue
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.
You're at greatest risk of polio if you haven't been immunized against the disease. In areas with poor sanitation and sporadic or nonexistent immunization programs, the most vulnerable members of the population — pregnant women, the very young and those with weakened immune systems — are especially susceptible to experience paralysis if they are infected with poliovirus.
These factors also increase your risk if you haven't been vaccinated:
- Travel to an area where polio is common or that has recently experienced an outbreak
- Living with or caring for someone who may be shedding poliovirus
- A compromised immune system, such as occurs with HIV infection
- Having had your tonsils removed (tonsillectomy)
- Extreme stress or strenuous physical activity after being exposed to poliovirus, both of which can depress your immune system
Paralytic polio can lead to temporary or permanent muscle paralysis, disability, and deformities of the hips, ankles and feet. Although many deformities can be corrected with surgery and physical therapy, these treatments may not be options in developing nations where polio is still common. As a result, children who survive polio may spend their lives with severe disabilities.
Although improved public sanitation and careful personal hygiene may help reduce the spread of polio, the most effective way to prevent the disease is with polio vaccine.
Currently, most children in the United States receive four doses of inactivated poliovirus vaccine (IPV) at the following ages:
- Two months
- Four months
- Between 6 and 18 months
- Between ages 4 and 6 when children are just entering school
IPV is 90 percent effective after two shots and 99 percent effective after three. It can't cause polio and is safe for people with weakened immune systems, although it's not certain just how protective the vaccine may be in cases of severe immune deficiency. Common side effects are pain and redness at the injection site.
Allergic reaction to the vaccine
IPV can cause an allergic reaction in some people. Because the vaccine contains trace amounts of the antibiotics streptomycin, polymyxin B and neomycin, it shouldn't be given to anyone who's had a reaction to these medications.
Signs and symptoms of an allergic reaction usually occur within minutes to a few hours after the shot and may include:
- Difficulty breathing
- Hoarseness or wheezing
- Rapid heart rate
- Unusual paleness
- Swelling of the throat
If you or your child experiences an allergic reaction after any shot, get medical help immediately.
Fewer shots for your child
Polio vaccine is normally given in conjunction with vaccinations against other diseases, including diphtheria, tetanus and acellular pertussis (DTaP), pneumococcal infections, and hepatitis B. But your child may not need to receive all these injections separately.
A combination vaccine called Pediarix is available that reduces the number of injections given during the first two years of life. Pediarix combines DTaP, hepatitis B and polio vaccine into a single vaccine. Side effects of Pediarix are similar to those of the individual vaccines administered separately, though fever is more likely to occur in children who receive Pediarix than in children who receive vaccines separately.
In the U.S., adults aren't routinely vaccinated against polio because most are already immune and the chances of contracting polio are minimal. However, certain adults at high risk of polio who have had a primary vaccination series with either IPV or the oral polio vaccine (OPV) should receive a single booster shot of IPV. A single booster dose of IPV lasts a lifetime. Adults at risk include those who are traveling to parts of the world where polio still occurs or those who care for people who may be excreting wild poliovirus.
If you're unvaccinated or your vaccination status is undocumented, get a series of primary polio vaccination shots — two doses of IPV at four– to eight–week intervals and a third dose six to 12 months after the second dose.