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.

Nonparalytic polio
Some people who develop symptoms from the poliovirus contract nonparalytic polio — a type of polio that doesn't lead to paralysis (abortive poliomyelitis). This usually causes the same mild, flu-like signs and symptoms typical of other viral illnesses.

Signs and symptoms, which generally last two to 10 days, include:

• Fever
• Sore throat
• Headache
• Vomiting
• Fatigue
• Back pain or stiffness
• Neck pain or stiffness
• Pain or stiffness in the arms or legs
• Muscle spasms or tenderness
• Meningitis

Paralytic polio
Fewer than 1 percent of people infected with poliovirus develop paralytic polio, the most serious form of the disease. Initial signs and symptoms of paralytic polio, such as fever and headache, often mimic those of nonparalytic polio. Between one and 10 days later however, signs and symptoms specific to paralytic polio appear, including:

• Loss of reflexes
• Severe muscle aches or spasms
• Loose and floppy limbs (acute flaccid paralysis), often worse on one side of the body

The onset of paralysis may be sudden.

Classifications of paralytic polio
Paralytic polio has historically been divided into several types, depending primarily on which part of the body is affected. These classifications aren't rigid, and overlap may occur among the different forms.

• Spinal polio. This most common form of paralytic polio attacks certain nerve cells (motor neurons) in your spinal cord and may cause paralysis of the muscles that control breathing and those in your arms and legs. Sometimes the neurons are only damaged, in which case you may recover some degree of muscle function. But if the neurons are completely destroyed, the paralysis is irreversible, although you still retain your sense of feeling, unlike after many spinal cord injuries.
• Bulbar polio. In this severe type of polio, the virus affects the motor neurons in your brainstem, where the centers of the cranial nerves are located. These nerves are involved in your ability to see, hear, smell, taste and swallow. They also affect the movement of muscles in your face and send signals to your heart, intestines and lungs. Bulbar polio can interfere with any of these functions but is especially likely to affect your ability to breathe, speak and swallow and can be fatal without respiratory support.
• Bulbospinal polio. A combination of both bulbar and spinal paralytic polio, this form can lead to paralysis of your arms and legs and may also affect breathing, swallowing and heart function.

Post-polio syndrome
Affecting some people who have recovered from polio, post-polio syndrome is a cluster of disabling signs and symptoms that appears decades — an average of 30 to 40 years — after the initial illness. 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

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

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

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. Although people carrying the poliovirus are most contagious seven to 10 days before and after signs and symptoms appear, they can spread the virus for weeks in their feces.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

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 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
• Handling laboratory specimens that contain live 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

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

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 endemic. As a result, children who survive polio may spend their lives with severe disabilities.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

Doctors often recognize polio by symptoms such as neck and back stiffness, abnormal reflexes, and difficulty swallowing and breathing. To confirm the diagnosis, a sample of throat secretions, stool or cerebrospinal fluid — a colorless fluid that surrounds your brain and spinal cord — is checked for the presence of poliovirus.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

Because no cure for polio exists, the focus is on increasing comfort, speeding recovery and preventing complications. Supportive treatments include:

• Bed rest
• Antibiotics for secondary infections (none for poliovirus)
• Analgesics for pain
• Portable ventilators to assist breathing
• Moderate exercise (physiotherapy) to prevent deformity and loss of muscle function
• A nutritious diet

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

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.

Polio vaccine
Currently, most children in the United States receive four doses of inactivated poliovirus (IPV) at the following ages:

• 2 months
• 4 months
• Between 6 and 18 months
• A booster shot, between ages 4 and 6 years 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:

• High fever
• Difficulty breathing
• Weakness
• Hoarseness or wheezing
• Rapid heart rate
• Hives
• Dizziness
• 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 other vaccinations, including diphtheria, tetanus and acellular pertussis (DTaP); hepatitis B-Haemophilus influenzae type b (HBV-Hib); and pneumococcal conjugate vaccine (PCV). 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 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.

Adult vaccination
In the U.S., adults aren't routinely vaccinated against polio because most are already immune and the chances of contracting wild 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 dose 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, you should receive a primary polio vaccination series with IPV — two doses at four- to eight-week intervals and a third dose six to 12 months after the second dose.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.