Outbreaks of disease have had a profound effect on human existence. From the time of the pharaohs to the present day, epidemics of diseases like the bubonic plague, cholera, influenza, and smallpox have had a cataclysmic impact on civilizations. These scourges changed history, accelerated the decline of empires, decimated armies, and molded cultures.
One such outbreak occurred 100 years ago. Just as World War I was ending, the Spanish flu devastated nations all around the world, killing about 20 million people by some estimates.
To mark the anniversary of this event, 24/7 Wall St. has compiled a list of the worst outbreaks of all time.