Polio (poliomyelitis) mainly affects children under five years of age but adults may also develop the disease.
In about 95 percent of polio cases, infection from the polio
virus causes no symptoms or serious effects (asymptomatic polio).
In about 5 percent of polio cases, the polio virus manifests in a
mild form (abortive polio) with flu-like symptoms, in a
nonparalytic form (aseptic meningitis) or in a severe form called
paralytic polio.
People who have minor or nonparalytic forms can recover completely.
A small percentage of those who did fully recover might go on to
develop post-polio syndrome (PPS) as many as 30 to 40 years after
contacting polio. In PPS, the damage done to the nerves during the
disease causes an acceleration of the normal, gradual weakness due
to aging.