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Symptoms of Poliomyelitis
Symptoms of the disease can start 7-14 days after infection, but usually 7-10 days. Even in people who have not been vaccinated, about 95% of cases of polio are mild, causing a brief, unidentified illness with headache, fever and sometimes vomiting, that lasts for a few days and passes with no ill effects. However, in some cases this stage is followed by a very serious illness.
If the body’s immunity is insufficient, the viruses multiply in the throat and the bowel, invade the bloodstream and are carried to the nervous system. Serious illness is more likely if the tonsils have recently been removed or some other inoculation has been given, or if there is much physical exertion at the time the viruses reach the nervous system.
The acute stage features severe headache, neck stiffness, high fever and progressive muscle weakness (paralysis). The paralysis is worst at the end of the first week of the severe symptoms, and thereafter there may be gradual recovery. Any muscle that has shown no sign of movement by the end of a month is likely to be permanently paralysed.
If the upper part of the spinal cord or the brain stem is involved, the patient may develop a bulbar palsy. This features progressive paralysis of the tongue, throat and voice box (larynx) so that swallowing and speaking become difficult or impossible.
More seriously, the parts of the brain stem concerned with breathing may be destroyed. In such an event the person concerned can be kept alive only by continuous artificial respiration (ventilation) by a mechanical pump.
