Polio

Though it's been around since ancient times, polio, which targets the nervous system, only rose to epidemic proportions in the 20th century, perhaps because increased population density facilitated its transmission.

At its worst, polio was serious business: some patients were left with life-long limb paralysis or deformities, while an even unluckier few found their respiratory muscles paralyzed and were left dependent upon coffin-like iron lungs for their survival. Many eventually died. Amazingly, up to 95 percent of people infected with polio showed no symptoms, and most others just faced your standard flu-like fare … but those numbers can be misleading.

At the height of the polio epidemic in the 1950s, there were over 13,000 cases involving paralysis and 1,000 deaths each year from the disease, many of them children.

Thanks to a large-scale vaccination campaign, polio is no longer a problem in most of the world, but remains endemic in parts of India, Pakistan and Nigeria.

Source; http://science.discovery.com/life-earth-science/10-infectious-diseases.htm