Polio has been around since ancient times. This ancient Egyptian tomb painting shows a man with a withered leg unable to bear weight without use of a walking stick. This means that most muscle fibers are replaced with scarring (muscle-wasting) that is permanent.

If someone had polio as a child or young adult but had kept or recovered some or all movement of weakened arms or legs, even to the point of being athletic afterward, they can risk becoming weaker in late adulthood. That is post-polio syndrome (PPS), a condition that can affect polio survivors decades after they recover from their initial poliovirus infection. Some PPS patients become wheelchair-bound when they had not been before.

Polio, or poliomyelitis, is an infectious viral disease that can strike at any age and affects a person's nervous system. Post-polio syndrome (PPS) is a non-contagious condition that can affect polio survivors usually 15 to 40 years after recovery from polio. Only a polio survivor can develop PPS, it is not contagious.

The polio vaccine has eradicated polio from the United States. However, polio still exists in some countries and cases of PPS still arise.

Poliovirus is a member of the Enterovirus genus, family Picornaviridae. Enteroviruses are transient inhabitants of the gastrointestinal tract, and are stable at acid pH. Picornaviruses are small, ether-insensitive viruses with an RNA genome. Poliovirus causes polio, or poliomyelitis, a highly infectious disease.

There are three poliovirus serotypes (PV1, PV2, and PV3) with minimal heterotypic immunity between them. That is, immunity to one serotype does not produce significant immunity to the other serotypes.

Poliovirus infects only humans. Poliovirus is spread by the fecal-oral and respiratory routes. Infection is more common in infants and young children. Polio occurs at an earlier age among children living in poor hygienic conditions. In temperate climates, poliovirus infections are most common during summer and autumn. In tropical areas, the seasonal pattern is less pronounced.

What is post-polio syndrome?

Post-polio syndrome (PPS) is a condition that affects polio survivors many years after recovery from an initial attack of the poliomyelitis virus. PPS is characterized by a further weakening of muscles that were previously affected by the polio infection. PPS is not contagious. The most common symptoms include:

• slowly progressive muscle weakness
• fatigue (both general and muscular)
• decrease in muscle size (muscular atrophy)
• loss of muscle function
• pain from joint deterioration and increasing skeletal deformities such as curvature of the spine (scoliosis)

Some individuals experience only minor symptoms, while others develop more visible muscle weakness and atrophy. PPS is rarely life-threatening but the symptoms can interfere significantly with the individual's capacity to function independently.

Is there any treatment?

There are currently no effective treatments that can stop deterioration or reverse the deficits caused by the syndrome itself, but there are recommended management strategies. Individuals with PPS should seek medical advice from a physician experienced in treating neuromuscular disorders.

Treatments for symptoms include:

• non-fatiguing exercises (those that do not cause pain or fatigue lasting more than 10 minutes) may improve muscle strength and reduce tiredness. Exercise should be considered under the supervision of an experienced health professional.
• cardiopulmonary endurance training
• mobility aids and ventilation equipment
• counseling to help individuals and families adjust to the late effects of poliomyelitis

Physicians recommend that polio survivors get a good night’s sleep, maintain a well-balanced diet, avoid unhealthy habits such as smoking and overeating, and follow a prescribed exercise program. Lifestyle changes, such as weight control, the use of assistive devices, and taking certain anti-inflammatory medications, may help with some of the symptoms of PPS.

What is the prognosis?

PPS is a very slowly progressing condition marked by long periods of stability. The severity of PPS depends on the degree of the residual weakness and disability an individual has after the original polio attack. People who had only minimal symptoms from the original attack and subsequently develop PPS will most likely experience only mild PPS symptoms. People originally hit hard by the polio virus, who were left with severe residual weakness, may develop a more severe case of PPS with a greater loss of muscle function, difficulty in swallowing, and more periods of fatigue.

The cause of PPS is unknown. The new weakness of PPS appears to be related to the degeneration of individual nerve terminals in the motor units. A motor unit is formed by a nerve cell (or motor neuron) in the spinal cord or brain stem and the muscle fibers it activates. The polio virus attacks specific neurons in the brain stem and spinal cord. Surviving cells sprout new nerve-end terminals and connect with other muscle fibers. These new connections may result in recovery of movement and gradual gain in power in the affected limbs.

Years of high use of these recovered but overly extended motor units add stress to the motor neurons, which over time results in the slow deterioration of the neurons and leads to loss of muscle strength. Restoration of nerve function may occur in some fibers a second time, but eventually nerve terminals malfunction and permanent weakness occurs. This may be why PPS occurs after a delay and has periods of relative stability combined with periods of decline with progressive weakness.

Most often, polio survivors start to experience gradual new weakening in muscles that were previously affected by the polio infection. Some individuals experience only minor symptoms while others develop visible muscle weakness and atrophy. A person who was more acutely affected by polio and who attained a greater recovery may experience a more severe case of PPS.

Symptoms include:

• slowly progressive muscle weakness
• fatigue
• a gradual decrease in the size of muscles (muscle atrophy)
• loss of muscle function
• pain from joint degeneration and increasing skeletal deformities such as curvature of the spine (scoliosis)

PPS is rarely life-threatening, but the symptoms can significantly interfere with an individual's ability to function independently. Respiratory muscle weakness, for instance, can result in trouble with proper breathing, affecting daytime functions and sleep. Weakness in swallowing muscles can result in aspiration of food and liquids into the lungs and lead to pneumonia.

There are no laboratory or diagnostic tests specific for PPS. Physicians diagnose the condition after completing a comprehensive medical history and physical examination, and by excluding other disorders that could explain the symptoms.

Physicians look for the following criteria when diagnosing PPS:

• Prior paralytic poliomyelitis with evidence of motor neuron loss. This is confirmed by history of the acute paralytic illness, signs of residual weakness and muscle atrophy, and signs of motor neuron loss on electromyography (EMG).
• A period of partial or complete functional recovery after acute paralytic poliomyelitis, followed by an interval (usually 15 years or more) of stable neuromuscular function.
• Slowly progressive and persistent new muscle weakness or decreased endurance, with or without generalized fatigue, muscle atrophy, or muscle and joint pain. Onset may at times follow trauma, surgery, or a period of inactivity, and can appear to be sudden. Less commonly, symptoms attributed to PPS include new problems with breathing or swallowing.
• Symptoms that persist for at least a year.
• Exclusion of other neuromuscular, medical, and skeletal abnormalities as causes of symptoms.

Diagnostic tests include:

• magnetic resonance imaging (MRI) and computed tomography (CT) of the spinal cord
• electrophysiological studies and other tests to investigate the course of decline in muscle strength and exclude other diseases that could be causing or contributing to the new progressive symptoms
• muscle biopsy
• spinal fluid analysis to exclude other, possibly treatable, conditions that mimic PPS

There are currently no effective treatments that can stop deterioration or reverse the deficits caused by the syndrome itself, but there are recommended management strategies. Individuals with PPS should seek medical advice from a physician experienced in treating neuromuscular disorders.

A number of research studies have demonstrated that non-fatiguing exercises (those that do not cause pain or fatigue lasting more than 10 minutes) may improve muscle strength and reduce tiredness. Cardiopulmonary endurance training also is helpful. Exercise should be considered under the supervision of an experienced health professional.

Mobility aids, ventilation equipment, and revising activities of daily living activities can help to avoid rapid muscle tiring and total body exhaustion.

Counseling may help individuals and families adjust to the late effects of poliomyelitis. Support groups that encourage self-help, group participation, and positive action can be helpful.

Physicians recommend that polio survivors get a good night’s sleep, maintain a well-balanced diet, avoid unhealthy habits such as smoking and overeating, and follow a prescribed exercise program. Lifestyle changes, such as weight control, the use of assistive devices, and taking certain anti-inflammatory medications, may help with some of the symptoms of PPS.

Polio, or poliomyelitis, is a crippling and potentially deadly disease. It is caused by the poliovirus. The virus spreads from person to person and can invade an infected person’s brain and spinal cord, causing paralysis (can’t move parts of the body).

Polio can be prevented with vaccine. Inactivated polio vaccine (IPV) is the only polio vaccine that has been given in the United States since 2000. It is given by shot in the arm or leg, depending on the person’s age. Oral polio vaccine (OPV) is used in other countries.

CDC recommends that children get four doses of polio vaccine. They should get one dose at each of the following ages:

• 2 months old
• 4 months old
• 6 through 18 months old
• 4 through 6 years old

Almost all children (99 out of 100) who get all the recommended doses of polio vaccine will be protected from polio.

The first polio vaccine was available in the United States in 1955. Thanks to widespread use of polio vaccine, the United States has been polio-free since 1979. But poliovirus is still a threat in some countries. It takes only one traveler with polio to bring the disease into the United States. The best way to keep the United States polio-free is to maintain high immunity (protection) in the U.S. population against polio through vaccination.

At the National Institutes of Health (NIH), the National Institute of Allergy and Infectious Diseases (NIAID) is the leading funder of PPS research. The National Institute of Neurological Disorders and Stroke (NINDS) is the leading funder of research on neuromuscular disorders. NIH is the leading supporter of biomedical research in the world.

Scientists are working on a variety of investigations that may one day help individuals with PPS. Some basic researchers are studying the behavior of motor neurons many years after a polio attack. Others are looking at the mechanisms of fatigue and are trying to learn more about its possible causes. Researchers also are developing and refining interventions to help people with chronic conditions more effectively manage fatigue and sleep disturbances.

Determining if there is an immunological link in PPS also is an area of interest. Researchers who discovered inflammation around motor neurons or muscles are trying to find out what causes this immunological response.