The Probert Encyclopaedia of Medicine

POLIO

Polio (properly poliomyelitis, and also known as infantile paralysis) is caused by infection of the nervous system by a virus which gains entry through the nasopharynx and breeds in the intestinal mucous lining. It is expelled in the faeces. The blood stream carries the disease to the nervous system. There the virus attacks the cells lying in the grey matter of the brain and spinal cord, and in a case of very severe infection certain of these nerve cells may be entirely destroyed. This affection of the nerve cells leads to the characteristic symptom of the disease, namely muscular paralysis. A striking feature of the disease is its occurrence in young children, especially in those between the ages of two and four years. It may occur also in adolescence and early adult Life, but is rare after middle age. During an epidemic the virus may attack many people without giving rise to actual paralysis in any part of the body, and it has been found that over 50 per cent of the adult population have the special antibodies against the virus in the blood, showing that they have at some time suffered from a mild or unrecognised attack.
Confirmation of these facts was found in an American epidemic in the 1950s. Amongst twenty-two contacts of a case of infantile paralysis, fourteen were found to have the virus in the faeces. Fourteen of the twenty-two cases developed slight fever, but only one became paralysed. The disease is spread by human carriers of the virus, who may or may not be ill with the disease. The secretions of the nose and throat are infective during the first ten days of the illness, and spread of the disease mainly takes place from one person to another by what is known as 'droplet infection' (as in sneezing, coughing, talking, etc.), and by the common use of articles recently contaminated by these secretions. The virus may be present also in the faeces of a patient up to three months after his apparent recovery.
The disease may also be spread by infected water, milk or fruit, either by direct handling, or by flies carrying infection from lavatories or sewage. The disease is much more prevalent during the hotter months of the summer, and in the European climate it reaches its maximum frequency in August and September. The incubation period varies between six and ten days, the average being nine days. Infantile paralysis begins suddenly with fever lasting from one to five days, the temperature rising to 102 or 104 degrees. The child is usually flushed and drowsy, but may be very irritable, and vomiting and convulsions may occur. There is headache, with pain in the neck and back, and tenderness of the limbs. The symptoms at this stage are similar to those seen in many other acute infectious diseases, though special significance should be attached to severe pains in the limbs and tenderness of the muscles. In one to five days the characteristic signs of paralysis appear in one or more groups, of muscles. In older children and adults the paralysis is usually present within twenty-four hours of the onset. It develops rapidly and appears to have its maximum limit of distribution from the moment it appears. It is, in fact, usually much more widespread at the onset than it is destined to be permanently.
At first all four limbs may appear to be completely helpless, but after some days a rapid recovery occurs from much of the paralysis, so that only one limb may be finally affected. The narrowing down of the initial paralysis begins to appear after the end of the first week, and any muscle which is going to recover its power will have done so before the end of the first month. The muscles which are permanently paralysed become atrophied, or wasted, and in the course of time they tend to become contracted or shortened. This shortening may lead to considerable deformity of the part unless it is prevented by suitable treatment. The paralysis may affect any of the muscles of the body, but those of the leg are far more commonly involved than any others.
Research Polio