I.

Introduction

Poliomyelitis, infectious viral disease, commonly called polio, that sometimes causes temporary or permanent paralysis. The infection chiefly affects children and young adults. More than 95 percent of polio infections produce no noticeable symptoms or mild symptoms that last only a few days. In the remainder the virus enters the nervous system and infects nerve cells that control muscles. It can then cause paralysis, most often of the legs. In its most dangerous form, the polio virus attacks the brain, creating complications that sometimes result in death. Because of polio’s prevalence among young children, it was sometimes called infantile paralysis.

Polio once ranked among the most dreaded diseases in much of the world. The disease most often struck in summer and early fall. Fearing infection, many people avoided beaches, public pools, theaters, fairs—any place of public gathering. Occasionally schools were closed until epidemics subsided. Paralysis was frightening. Especially terrifying was the thought of lying immobile in an “iron lung”—an artificial breathing device for polio patients who could no longer breathe by themselves.

The fight against polio represents one of the great medical success stories of the 20th century. In much of the world, polio went from a feared disease to mostly a memory in little more than half a century. The introduction of vaccines that protect against polio in the 1950s, along with successful vaccination programs, virtually wiped out polio in developed countries. Vaccination efforts continue in developing countries of Asia and Africa.