1930s, two strains of the poliovirus are discovered (later it was determined that there were three).
1931, scientists create the first filter able to trap viruses.
1933, FDR inaugurated president of the United States.
1935, Maurice Brodie and John Kolmer test polio vaccines, with disastrous results.
1938, FDR founds the National Foundation for Infantile Paralysis, known today as the March of Dimes.
1940s, Sister Kenny, an Australian nurse, comes to the U.S. to promote her new treatment for polio, using warm compresses to relax painful, contracting muscles and massage for rehabilitation.
1947 - 50, Dr. Jonas Salk is recruited by the University of Pittsburgh to develop a virus research program.