Humanity is nothing if not resilient. Need proof? Just consider everything weve survived so far! For this list, well be looking at the deadliest and most significant outbreaks of contagious disease throughout human history. Our countdown includes the 2009 Flu Pandemic, the 1772 Persian Plague, 1520 Smallpox Epidemic, and more! What do YOU think is the worst epidemic in history? Let us know in the comments! Watch more great worst of videos here: Top 10 Worst Movie Outbreaks: