Cholera

We haven't had a major outbreak of cholera in the US for a hundred years, but it's still a leading cause of death in the developing world.  Mortality rate is 50% if left untreated.  Of course, many famous pandemics throughout history, and it's frequently incoporated into major works of literature. It turned up in Haiti last week, and is "creeping" toward the capital city.  Not good.