Before 1492, Indigenous societies lived in a different ecological disease landscape than Eurasia. Fewer herd animals and lower population density meant fewer “crowd diseases,” but people still navigated a mix of endemic infections, parasites, fungi, and occasional epidemics whose signatures survive in bones, coprolites, and now ancient DNA.

A quick tour of the regions:

Arctic/Subarctic:
Small, mobile foraging societies faced zoonotic parasites tied to raw marine and terrestrial foods such as trichinellosis, fish tapeworm, echinococcus. Tuberculosis existed at low levels (confirmed by aDNA), possibly through coastal or Norse contact (speculated but unconfirmed), but major epidemics likely didn’t occur here.

Temperate North America:
Treponemal disease (yaws/bejel-like) was widespread, with characteristic bone lesions at sites like Chaco Canyon and Mississippian mound centers. TB shows up again. It likely arrived from the south via trade, as it matches the Peruvian seal-derived strain. Parasitic infections increased with agriculture. The desert Southwest uniquely battled coccidioidomycosis (Valley Fever); skeletal cases show disseminated fungal infection centuries before European contact.

Mesoamerica:
Urban density, irrigation agriculture, and long-distance trade supported persistent waterborne diseases and intestinal parasites. Triatomine-borne Chagas disease was endemic; one 14th-century epidemic near Lake Texcoco described swollen eyelids, hemorrhagic diarrhea, and high mortality—consistent with acute Chagas. Arboviruses likely circulated at low levels, though they leave little archaeological trace.

Altogether, the Americas hosted a patchwork of region-specific infections shaped by ecology, subsistence, and settlement patterns. 

Happy to answer questions or add diseases I missed.

What Infectious Diseases Existed in the Americas Before 1492? Part 1: A Tour Through Arctic, Plains, Southwest, and Mesoamerican Disease Ecology