Polio virus infection
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Poliomyelitis is caused by three types of polio virus. Type 1 polio virus is the most virulent and prior to immunization was responsible for major epidemics.
Polio virus is an enterovirus and is spread by the feacal-oral route.
Other factors associated with paralysis are: pregnancy, tonsillectomy and prophylactic injections.
The incubation period is 3-21 days (usually 7-14 days).
Clinical features: There is a flu-like prodromal illness. The symptoms may resolve at this stage (abortive infection) or may progress to aseptic meningitis. The meningitis may be complicated by flaccid paralysis which may be bulbar or spinal. Occasionally in children paralysis may be the first symptom of infection.
Diagnosis:
1. Characteristic clinical features (NB no sensory deficit)
2. CSF leucocytosis (neutrophils may predominate initially), raised CSF protein.
3. Isolation of virus from the stool or from a throat swab.
Treatment is supportive, and most efforts should be directed towards prevention by immunization: the Sabin vaccine, oral polio vaccine, is a live attenuated vaccine incorporating antigens from the three virus types.
