Viral infection of the central nervous system
affecting nerves that activate muscles. The
disease used to be known as infantile
paralysis. The World Health Organization
expects that polio will be eradicated by
2000. The polio virus is a common one, and
mostly, its effects are confined to the
throat and intestine, as in flu or a mild
digestive upset. There may also be muscle
stiffness in the neck and back. Paralysis is
seen in about 1% of cases, and the disease is
life-threatening only if the muscles of the
throat and chest are affected. Cases of this
kind, once entombed in an `iron lung', are
today maintained on a respirator. Two kinds
of vaccine are available, one injected (see
Salk) and one given by mouth.