Polio is a viral infection of humans that occasionally spreads to the central nervous system. Once this happens, permanent muscle paralysis development often occurs. These cases only occur when the polio virus attacks and destroys the spinal cord and brain tissue that controls muscle activity. It's transmitted through oral ingestion of virus present in the stool of infected individuals and saliva. Most people do not have symp-toms when they are infected with polio. Only about 5% …showed first 75 words of 1126 total…

…showed last 75 words of 1126 total…are also medical scientists. In 1977, he received the Presidential Medal of Freedom. Dr. Salk's last years were spent investigating for a vaccine against AIDS. Jonas Salk died 80 years old on June 23, 1995 of congestive heart failure. Jonas Salk is a very dedicated scientist and has been very successful in his years of research. He saved millions of lives and has ended the suffering of thousands more. Jonas Salk is considered a hero to all polio victims.