It is an acute disease characterised by destructive lesions in the grey matter of the spinal chord and brain; there is degeneration of the cells in the anterior horns. There is inflammation of the leptomeninges, particularly over the anterior fissure of the cord. The cerebral and cerebellar cortex, the basal ganglia and brain stem may also be affected.
Paralysis is not an essential feature of Poliomyelitis. The incidence of paralytic cases gives a very erroneous impression of the actual prevalence of this disease. The presence of neutralising antibodies in the blood serum of from 50 to 60 per cent adult population indicates that a large proportion of urban dwellers have suffered from an unrecognised or abortive attack of Poliomyelitis.
The disease is caused by a neurotropic virus which is probably transmitted from person to person through the transfer of the secretions of the nose and throat by droplet infection, by fingers and the common use of articles recently contaminated with these secretions. The virus attaches itself to the olfactory hair, ascends by way of the olfactory nerves and invades the nerve cells with more or less extensive spread from brain to spinal cord. There is another and more probably way of communication of the disease in which infection spreads by mouth by infected milk or water and by insect vectors.
The virus multiplies chiefly in the walls of the pharynx and small intestine. It passes to the central nervous system through the pharyngo-tonsillar or intestinal mucous membrane, travelling along autonomic nerves to the medulla or spinal cord. The infection may pass along parasympathetic fibres in the 7th., 9th., or 10th. Cranial nerves, along sympathetic fibres to the thoraco-lumbar region, and along parasympathetic fibres to the sacral region.
Carriers and unrecognised or abortive cases play a very important part in the spread of this serious disease.
The virus has been isolated from the naso-pharynx during the third week of convalescence. It is excreted in the faeces, and can be detected in the faeces of patients suffering from the paralytic and the common abortive types of the disease. It may be present in the faeces in convalescence for over three months.
The incubation period appear to vary from 5 to 17 days, the average period being from 9 to 12 days. The patient must be promptly and effectively isolated. Children who have been in contact with the patient should be strictly quarantined and kept under medical observation for a period of three weeks from the date of last contact.
Adults may continue their occupation so long as they can avoid mixing with children, but they should avoid all social activities for a period of three weeks from the date of the last contact; kissing or playing with young children must bee strictly forbidden. Where a profession necessitates coming in contact with children (as in the case of nurses and school teachers), even the adults must be quarantined.
If a person coming in contact with a case of Poliomyelitis suffers from a febrile catarrh or other symptoms suggestive of an abortive attack of the disease, he should be strictly isolated till recovery. Children should not sleep together in the same bed, nor use a common handkerchief. They should spend as much time in the open air as possible.
During epidemic prevalence of Poliomyelitis, tonsillectomy operations should be postponed as it has on some occasions transformed a milk sub-clinical poliomyelitic infection into a fatal bulbar type of the disease.
THE ONSET AND COURSE OF THE DISEASE.
The patient is taken ill comparatively suddenly, with headache, malaise, fever, drowsiness, pains in the neck, back and limbs, nausea, vomiting, diarrhoea, and perhaps convulsions. Rigidity of the neck and signs of meningeal irritation develop, and the headache may be very intense. Small and uncontrolled movements of the fingers and hands may be noticeable.