myelitis, infectious virus disease of the central nervous system, sometimes resulting in paralysis. The greatest incidence of the disease, also known as infantile paralysis, is in children between the ages of five and ten years. The disease was described in 1840 by the German orthopedist Jacob von Heine. In its clinical form it is more prevalent in temperate zones. The virus usually enters the body through the alimentary tract and spreads along nerve cells to affect various parts of the central nervous system. The incubation period ranges from ....