In modern times, a strain of salmonella called Paratyphi C. causes a typhus-like outbreak called enteric fever that can kill as many as 15% of those it infects, mostly in developing countries. Now, evolutionary geneticists think this strain of salmonella could be what sickened and killed millions of natives in Mexico in the 1500s, essentially bringing about the collapse of the Aztec empire. Reporting on the bioRxiv server, researchers say they sequenced fragments of DNA taken from the teeth of 29 bodies buried in the Oaxacan highlands of Mexico after an outbreak around 1550. In those fragments, they saw evidence of the salmonella strain. "It’s a super-cool study," one ancient-DNA researcher not involved in the work tells Nature. "They make a really good case."
For centuries, people have wondered what wiped out the native population of 25 million, which plummeted to 1 million within 100 years of the 1519 arrival of Spanish conquistadors. During a second outbreak in 1576, the devastation was such that a historian wrote: "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." Researchers have ruled out typhus, measles, and smallpox, though one scientist not involved in this study is skeptical that salmonella is the primary cause of so many deaths; she contends that a virus could be responsible, given that the method used wouldn't have detected a virus. A post at Science Alert advises caution until the research is peer-reviewed. (Salmonella brought down more than half the guests at this wedding.)