Polio & Post-Polio Syndrome
What is Polio?
Polio is a crippling and potentially fatal infectious disease. There is no cure, but there are safe and effective vaccines. The strategy to eradicate polio is therefore based on preventing infection by immunizing every child until transmission stops and the world is polio-free.
Polio (poliomyelitis) is a highly infectious disease caused by a virus. It invades the nervous system and can cause irreversible paralysis in a matter of hours.
Who is most at risk of polio?
Polio can strike at any age, but it mainly affects children under five years old.
How is polio spread?
Polio is spread through person-to-person contact. When a child is infected with wild poliovirus, the virus enters the body through the mouth and multiplies in the intestine. It is then shed into the environment through the faeces where it can spread rapidly through a community, especially in situations of poor hygiene and sanitation. If a sufficient number of children are fully immunized against polio, the virus is unable to find susceptible children to infect, and dies out.
Young children who are not yet toilet-trained are a ready source of transmission, regardless of their environment. Polio can be spread when food or drink is contaminated by faeces. There is also evidence that flies can passively transfer poliovirus from faeces to food.
Most people infected with the poliovirus have no signs of illness and are never aware they have been infected. These symptomless people carry the virus in their intestines and can “silently” spread the infection to thousands of others before the first case of polio paralysis emerges.
For this reason, WHO considers a single confirmed case of polio paralysis to be evidence of an epidemic – particularly in countries where very few cases occur.
Most infected people (90%) have no symptoms or very mild symptoms and usually go unrecognized. In others, initial symptoms include fever, fatigue, headache, vomiting, stiffness in the neck and pain in the limbs.
Acute flaccid paralysis (AFP)
One in 200 infections leads to irreversible paralysis, usually in the legs. This is caused by the virus entering the blood stream and invading the central nervous system. As it multiplies, the virus destroys the nerve cells that activate muscles. The affected muscles are no longer functional and the limb becomes floppy and lifeless – a condition known as acute flaccid paralysis (AFP).
All cases of acute flaccid paralysis (AFP) among children under fifteen years of age are reported and tested for poliovirus within 48 hours of onset.
More extensive paralysis, involving the trunk and muscles of the thorax and abdomen, can result in quadriplegia. In the most severe cases (bulbar polio), poliovirus attacks the nerve cells of the brain stem, reducing breathing capacity and causing difficulty in swallowing and speaking. Among those paralysed, 5% to 10% die when their breathing muscles become immobilized.
No one knows why only a small percentage of infections lead to paralysis. Several key risk factors have been identified as increasing the likelihood of paralysis in a person infected with polio. These include:
- immune deficiency
- removal of the tonsils (tonsillectomy)
- intramuscular injections, e.g. medications
- strenuous exercise
Treatment and Prevention
There is no cure for polio, only treatment to alleviate the symptoms. Heat and physical therapy is used to stimulate the muscles and antispasmodic drugs are given to relax the muscles. While this can improve mobility, it cannot reverse permanent polio paralysis.
Polio can be prevented through immunization. Polio vaccine, given multiple times, almost always protects a child for life.
What is Post-Polio Syndrome?
Post-polio syndrome (PPS) is a condition that affects polio survivors anywhere from 10 to 40 years after recovery from an initial paralytic attack of the poliomyelitis virus. PPS is characterized by a further weakening of muscles that were previously affected by the polio infection. The most common symptoms include slowly progressive muscle weakness, fatigue (both general and muscular), and a decrease in muscle size (muscular atrophy). Pain from joint deterioration and increasing skeletal deformities such as scoliosis are common. 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. While polio is contagious, PPS is not transmissible.
Is there any treatment?
Presently, no prevention has been found that can stop deterioration.. Doctors recommend that polio survivors follow standard healthy lifestyle practices: consuming a well-balanced diet, exercising in moderation, and visiting a doctor regularly. There has been much debate about whether to encourage or discourage exercise for polio survivors or individuals who already have PPS. A commonsense approach, in which people use individual tolerance as their limit, is currently recommended. Preliminary studies indicate that intravenous immunoglobulin therapy may reduce pain, increase quality of life, and improve strength modestly.
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.