What is cocoliztli? Scientists 'identify' mystery illness that wiped out the Aztecs

Salmonella was brought over to South America by European settlers. The natives had no resistance to the bacteria and millions of people died as a result

Salmonella was brought over to South America by European settlers. The natives had no resistance to the bacteria and millions of people died as a result

Within five years, as many as 15 million people - an estimated 80 percent of the population - were wiped out in an epidemic the locals named "cocoliztli".

Symptoms of the second epidemic were high fever, headaches and bleeding from the eyes, mouth and nose, and death followed within three or four days.

More than 500 years ago, most of the Aztecs were wiped out from the face of the Earth by a bad epidemic.

Cocoliztli translates to "pestilence" in the Aztec language.

On Monday, scientists swept aside smallpox, measles, mumps, and influenza as likely suspects, fingering a typhoid-like "enteric fever" for which they found DNA evidence on the teeth of long-dead victims.

It is considered one of the deadliest epidemics in human history, approaching the severity of the bubonic plague that killed 25 million people in Europe in the 14th century.

"The 1545-50 cocoliztli was one of many epidemics to affect Mexico after the arrival of Europeans, but was specifically the second of three epidemics that were most devastating and led to the largest number of human losses", said Åshild Vågene of the University of Tuebingen in Germany, co-author of a study published yesterday in Nature Ecology & Evolution. Using new techniques in ancient DNA research, experts from the Max Plank Institute, Harvard University and the Mexican National Institute of Anthropology and History, identified Salmonella enterica Paratyphi C in skeletons left behind from the 1545-1550 cocoliztli epidemic.

Germs brought to Mexico by European colonizers spread and developed as diseases in the native people who had never encountered them before.

"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", is how Franciscan historian Fray Juan de Torquemada is cited as chronicling the period. Scientists now think they know what killed them.

"We can not say with certainty that S enterica was the cause of the cocoliztli epidemic", researcher Kirsten Bos said.

"We tested for all bacterial pathogens and DNA viruses for which genomic data is available", and salmonella enterica, the bacteria that causes typhoid fever, was the only germ detected, said Alexander Herbig, co-author of the study. The research team says it is possible other pathogens have remained undetected or "completely unknown". The salmonella strain, which was present in Europe during the Middle Ages, may have traveled to Mexico via domesticated animals from Spain.

"We can not say with certainty that salmonella enterica was the cause of the [second] cocoliztli epidemic", said team member Kirsten Bos. However, the team believe that Salmonella Enterica "is a strong candidate".

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