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.
Poliomyelitis, shortened, became polio. For a time, polio was called infantile paralysis, though it did not affect only the young. Cause of Polio. Polio is caused by one of three types of poliovirus (which are members of the Enterovirus genus).These viruses spread through contact between people, by nasal and oral secretions, and by contact with contaminated feces.oliomyelitis, shortened, became polio. For a time, polio was called infantile paralysis, though it did not affect only the young. Cause of Polio. Polio is caused by one of three types of poliovirus (which are members of the Enterovirus genus).