Poliomyelitis, better known as polio or infantile paralysis, is the infectious viral disease that sometimes results in paralysis. Polio was a big cause of death of children and many elderly adults in the 20th century. Over 100,000 people have been affected with polio since the 20th century, and a new 20,000 cases of the disease was reported in 1999. This major epidemic has brought about major changes in medical history, and does nothing but make more medical advances for finding the cure for polio today.
Polio is transmitted through physical contact in most cases. It usually enters the boy through the mouth and grows in the tonsils and lymph nodes. The virus then spreads to the intestines and is excreted from the body, which may cause either more polio cases because of the way human waste is disposed. Actually, that was how many people in the 20th century caught polio. Polio causes paralysis by spreading to the spinal cord. The destruction of the cells found here creates muscular weakness in the arms and legs, causing paralysis. How extreme the paralysis is depends on the area of the spinal cord that has been affected and how many cells located there were destroyed. Paralysis of the leg was most common in children under five years of age in the 20th century, and paralyses of all of the limbs were common in adults.
A few years after polio became more widespread in the United States, scientists tried to figure out its source and how to stop it. Applied research was used mainly in monkeys to see how polio acted in the body. With this research, a scientist named John Enders created the first polio vaccine. The vaccine was unsuccessful however because it killed many polio patients who had the vaccine or made the condition worse than it was in the patient. Later on, Jonas Salk develops the first successful "killed" vaccine. A killed vaccine contains all three weakened types of the poliovirus so that when given it can attack the virus no matter what kind of polio the patient had.