Deadly Aztec outbreak may have been Salmonella, study finds

January 19, 2018

With cities seemingly floating on water, stone temples and palaces, and warriors decked out in jaguar skins with obsidian blades, the Aztec Empire was the most powerful empire to ever exist in Central America. Now, researchers have found a possible factor contributing to the society’s downfall: Salmonella.

At its peak, the Aztec Empire was one of the most technologically advanced societies in the world, but its expansion was cut short in 1521, when it was conquered by Spanish colonizers. Then, in 1545 and again in 1576, a mysterious disease referred to as cocoliztli began to kill a huge percentage of the population — between seven million to 17 million, estimated to be between 45% and 90% of the entire region.

“This was a hugely devastating epidemic,” Kirsten Bos, one of the authors of a recent study investigating the outbreaks’ source, told Newsweek. “It was a cataclysmic population decline.”

The disease caused bleeding, vomiting and rashes — symptoms that have led historians and archaeologists to debate causes for years.

Now, thanks to a computer program called MALT, researchers have pieced together fragments of an ancient Salmonella strain found in DNA samples taken from a cocoliztli cemetery. What exactly did they find? A deadly but rare strain called Salmonella enterica Paratyphi C.

Researchers got their samples by drilling into the core of the teeth of skulls found at the burial site. Pathogens are often trapped inside of teeth when a person dies, remaining there for years.

The DNA fragments then had to be painstakingly reconstructed due to years of degradation — a puzzle with snippets of DNA being compared to the modern Salmonella genome until a complete picture was formed.

“It’s like a mirror that’s been shattered, and you have to try to put it back together somehow,” said Bos.

The study published by Bos and her colleagues says that researchers couldn’t really identify a source of the bacteria. Some say the bacteria was brought over by Spanish conquerors, while other evidence points to a local strain that was made worse by an ongoing drought, reports NPR.

The findings aren’t conclusive, the researchers admit. They say that the best way to know for sure that they’ve found the outbreaks’ cause is to identify more DNA samples from cocoliztli bodies located at different sites to compare.