Salmonella Killed Off Majority Of Aztecs, New Studies Suggest

Published February 21, 2017
Updated December 15, 2017
Published February 21, 2017
Updated December 15, 2017

Two studies have independently found that salmonella may have caused the 16th-century plagues that wiped out four-fifths of the Aztecs.

Aztec Men

Wikimedia Commons

Two new studies have found that a deadly version of salmonella may be what was behind two 16th-century epidemics that wiped out four-fifths of the Aztec population, reports.

These studies were posted on bioRxiv as preprints, meaning that the papers have not yet been peer-reviewed but were screened by the Cold Spring Harbor Laboratory before they were accepted.

One study tested stomach bacteria discovered in a burial site connected to the plagues in question, while the other extracted and sequenced DNA from the teeth of 29 people who died during the epidemics. Both studies found that salmonella was involved.

The first study may be the first genetic evidence of what killed vast numbers of Aztecs after Europeans arrived in the Americas, Hannes Schroeder, an ancient-DNA researcher at the Natural History Museum of Denmark in Copenhagen, told “It’s a super-cool study,” adding that salmonella could have certainly caused the epidemics.

Meanwhile, the second study recreated two genomes of a salmonella strain called Paratyphi C using damaged DNA fragments found in the teeth. According to, the Paratyphi C strain causes enteric fever and will kill 10 to 15 percent of people it infects if left untreated.

Perhaps this is what finally explains the Aztecs’ demise. When the Spanish arrived in Mexico in 1519, the Aztecs numbered roughly 25 million. After the epidemic and a hundred years later, the population had dropped to a little less than just 1 million. These epidemics — called “cocoliztli” or the word for pestilence in the Aztec language — killed roughly 7 to 18 million of the Aztec people.

“In the cities and large towns, big ditches were dug, and from morning to sunset the priests did nothing else but carry the dead bodies and throw them into the ditches,” wrote a Franciscan historian who witnessed the outbreaks, according to

Now, as these papers await publication, we may finally know what caused such devastation.

Next, check out these five diseases whose origins medical experts got entirely wrong, before finding out about the unearthed mummy child that upended scientists’ beliefs about one of history’s worst diseases.

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