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 probably many other plagues of Ancient Rome.
This article prompts me to reconsider this notion.
https://www.archaeology.org/issues/298-1805/trenches/6524-trenches-mexico-colonization-salmonella
This bacterium, which is relatively uncommon today, causes a highly virulent form of 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