I always believed that the infection that destroyed the indigenous populations in the Western Hemisphere was smallpox. Similarly, I thought that smallpox was the most likely culprit for Galen's Antonine Plague and as well as probably many of the other plagues of Ancient Rome.
This article makes me reconsider this notion.
https://www.archaeology.org/issues/298-1805/trenches/6524-trenches-mexico-colonization-salmonella
This bacterium, relatively uncommon today, causes an extremely virulent paratyphoid fever.
https://en.wikipedia.org/wiki/Paratyphoid_fever
Excavated structure at the northern edge of the Grand Plaza at Teposcolula-Yucundaa. Architectural investigations of the Grand Plaza resulted in the unexpected discovery of a large epidemic cemetery associated with the 1545-1550 cocoliztli epidemic. The cemetery was found to contain numerous mass burials, attesting to the catastrophic nature of the epidemic. Photo: Christina Warinner/Teposcolula-Yucundaa Archaeological Project
guy also known as gaius