There are currently more than 750 such areas in the National Wilderness Preservation System comprising over 109 million acres -- roughly 5% of the United States by area. Need a refresher from the other 95%? The Active Times picked 10 wild places in the lower 48 states that are truly wild.
Polio, which struck children disproportionately, could attack the central nervous system and cause muscle deterioration, paralysis and even death. American virologist Jonas Salk, who was born 100 years today on October 28, 1914, developed the worldâs first safe and effective polio vaccine.
Because his goal was to create a live attenuated vaccine, Dr. Sabin had to isolate the poliovirus strains and then passage the strains through a myriad of host cells in order to attain the right virulenceâstrong enough to illicit an immune response, but weak enough so as to not cause polio in the recipient.