In the 16th Century, over the course of five years, almost 80% of the Aztec population were wiped out due to an unknown disease that burnt through their villages, causing high fevers, bleeding from the mouth, nose and eyes and eventually lead to death. Without understanding the epidemic, the Aztecs named the phenomenon 'cocoliztli', their native word for 'pestilence'.

Scientists have pondered the potential cause of the cocoliztli epidemic for years, but only recently has new research uncovered what may have caused it.