Alternative Names acute paralytic poliomyelitis or APP, polio, type 1 poliovirus, paralytic poliomyelitis, nonparalytic poliomyelitis, infantile paralysis
Definition Poliomyelitis, or polio, is a virus that causes a mild, flu-like illness in some people but in others leads to nerve damage and paralysis. A vaccine to prevent polio was developed in the 1950s and since then the infection has been eliminated from Australia, the US and most of Europe. The virus reproduces in the digestive system and spreads through the blood to the rest of the body. The virus is spread to others through infected faeces or by airborne particles.
What is going on in the body? During an attack of polio, nerve cells in the spinal cord are damaged or destroyed. These nerve cells transmit nerve impulses to the muscles and cause them to move. Without these functioning nerve cells, the body cannot move. Some of these nerve cells survive, however, and they can send out new nerve connections. In these cases, persons can regain much of their muscle use.
What are the signs and symptoms of the infection? In a mild case of polio there may be no symptoms at all, or the symptoms may include:
What are the causes and risks of the infection? Polio is caused by the poliovirus. In countries where people are not routinely vaccinated against the disease, polio can be spread through infected faeces or through airborne particles.
What can be done to prevent the infection? Polio can be almost completely prevented with polio immunisation. There are still many parts of the world that are not vaccinated. The majority of cases occur in Indian, Asia, and Africa. Once everyone in the world has been vaccinated, people will not need to be immunised because the virus will die out. Routine vaccination is not recommended after a person is 18 years old.
How is the infection diagnosed? Polio may be suspected in a child who has paralysis on one side of the body that occurred after a short, flu-like illness. To diagnose the disease, a spinal tap is done to obtain a sample of cerebrospinal fluid. A throat culture is done, and the person's stool is tested to see if polio is present.
What are the long-term effects of the infection? The long-term effects of the disease include death, paralysis, and postpolio syndrome. In the past, when the muscles of the lungs were affected, polio almost always led to death. Nowadays less than 5% of persons with polio will die because the respiratory problems can be managed better. Only 1% to 2% of persons infected with polio get symptoms related to nerve damage. The rest of the people will get no symptoms or a minor flu-like illness.
After some years, the overburdened nerve cells can sometimes weaken and fail. This results in new muscle weakness, called postpolio syndrome. About half the people with polio will get postpolio syndrome.
What are the risks to others? Polio is very contagious. The virus is spread directly from the stool of an infected person to the mouth of a noninfected person. This is usually from contaminated hands or eating utensils.
What are the treatments for the infection? People with mild symptoms usually get better after several days of bed rest. Any additional infections are treated with antibiotics. People who have damage to their nerve cells need to have their symptoms treated.
Muscle spasms and pain are treated with medication and hot, moist packs.
Sometimes the nerves and muscles that control the bladder are affected. In this case, a urinary catheter can be inserted into the bladder to drain urine.
A ventilator, or artificial breathing machine, may be needed if the nerves and muscles of the lungs are damaged.
A firm bed with a footboard can be used for people with paralysis of the legs.
In cases of paralysis, physiotherapy can help prevent muscle damage while the disease is active. Once the virus is no longer active, physiotherapy can help keep the muscles functioning.
What are the side effects of the treatments? All medications have side effects. Antibiotics and analgesics have some side effects, such as stomach upset or allergic reactions. Treatments to help with breathing or urination may cause infections.
What happens after treatment for the infection? After the poliovirus is treated, the person will still need physiotherapy to gain strength and mobility. After many years, new nerve cells can begin to fail, resulting in muscle weakness. This is known as Postpolio syndrome.
How is the infection monitored? Monitoring is ongoing. postpolio syndrome develops very slowly. It is usually diagnosed after muscle strength testing is done over a long period of time.
Author: Terry Mason, MPH Reviewer: HealthAnswers Australia Medical Review Panel Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia Last Updated: 1/10/2001 Contributors Potential conflict of interest information for reviewers available on request
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