10 Worst Epidemics Ever

Few words in the English language encapsulate as much horror, misery and doom as "plague." After all, infectious diseases have inflicted a great deal of damage throughout the centuries. They've decimated whole populations, ended blood lines, claimed higher casualties than wars and played pivotal roles in charting the course of history.

#10 - New World Smallpox... 

Before European explorers, conquerors and colonists began to flood into the New World in the early 1500s, the Americas were home to an estimated 100 million native people. During the centuries that followed, epidemic diseases decreased that number to somewhere between 5 and 10 million [source: Yount]. While these people, such as the Incas and the Aztecs, had built cities, they hadn't resided in them long enough to breed the kind of diseases Europeans had, nor had they domesticated as many animals. When the Europeans arrived to the Americas, they brought with them a host of diseases for which the native peoples had no defense or immunity.

100 million to 5 million... only #10!  Read about 9 even more grim epidemics...

http://health.howstuffworks.com/10-worst-epidemics.htm