Polio, once easily transmitted and widespread among young children, is now rare in developed nations due to the development of the polio vaccine in the 1950s. Three related viruses cause polio (or poliomyelitis), a contagious disease. Children and adults can contract polio; however, children suffer more often from this condition, hence, it was once known as “infantile paralysis.”
This acute viral disease occurs sporadically and in epidemics. It is characterized clinically by fever, sore throat, headache, and vomiting. Neck and back stiffness also accompany polio. In the minor illness, only these symptoms may occur. The major illness, which may or may not be preceded by the minor illness, entails involvement of the central nervous system, stiff neck, pleocytosis in the spinal fluid, and possible paralysis. There may be subsequent atrophy of groups of muscles, ending in contraction and permanent deformity. The administration of vaccines now largely controls this disease.
In nearly 95 percent of polio cases, infection results in no symptoms or serious effects. In other cases, polio marks itself in a mild form, known as abortive polio. It results in flu-like symptoms, in a nonparalytic form (aseptic meningitis). A severe form, known as paralytic polio can also emerge. Those who acquire the minor or nonparalytic form recover completely. On the other hand, paralytic polio results in damage to the spinal cord and the brain, because the virus invades the central nervous system. It can result in weakness, paralysis, serious breathing problems or death. One long-term effect is permanent muscle weakness.
Post-polio syndrome (PPS) affects polio victims who have previously suffered from the disease. The conditions resulting from PPS are not life threatening, but do cause discomfort and can impair mobility. PPS affects from 20 to 40 percent of polio survivors and usually occurs 30 to 40 years after recovery from the initial infection. It is more likely to strike those who have had paralytic polio.
