Salk began his research into a polio vaccine in 1948, after receiving a grant from the University of Pittsburgh. For his work, Dr. Salk would be given many awards throughout the rest of his life, including the Presidential Medal of Freedom in 1977.
Polio attacks the nervous system, causing varying degrees of paralysis. Mostly striking infants, it could strike adults as well. Perhaps the most famous of it's victims was President Franklin D. Roosevelt, who became partially paralyzed after being struck with at the age of thirty-nine. In 1952 alone nearly 3,000 Americans had died from the disease.
The disease has not been wiped from the earth, and does pop up every once in awhile in the United States. Most cases are people who have immigrated from other countries, especially developing ones.