Gene analysis may have finally revealed what killed 15 million Aztecs

When Europeans arrived in North America, they carried with them pathogens against which the continent's native people had no immunity. And the effects could be devastating. Never was this more true than when smallpox wiped out 5-8 million Aztecs shortly after the Spanish arrived in Mexico around 1519. Even worse was a disease the locals called “huey cocoliztli" (or “great pestilence" in Aztec) that killed somewhere from 5 to 15 million people between 1545 and 1550. For 500 years, the cause of this epidemic has puzzled scientists. Now an exhaustive genetic study published in Nature Ecology and Evolution has identified the likely culprit: a lethal form of salmonella, Salmonella enterica, subspecies enterica serovar Paratyphi C. (The remaining Aztecs succumbed to a second smallpox outbreak beginning in 1576.)

In a paper published in Nature Ecology & Evolution, they describe how DNA extracted from the teeth of 29 skeletons buried in a cemetery in southern Mexico revealed previously unidentified traces of the salmonella enterica bacterium.

The bacterium is known to cause enteric fever, of which typhoid is an example. According to the study, the symptoms tally with those mentioned in records from the time, which describe victims developing red spots on the skin, vomiting, and bleeding from various body orifices.

The epidemic was one of several to hit the indigenous population soon after the arrival of Europeans in the early 16^th century. 

"When the Europeans arrived in Mexico, they brought with them lots of different diseases," Ashild Vagene, co-author of the study, told The Independent. "There were dozens of epidemics across the New World and Mexico was particularly hard hit."