It is known that the native population of the Americas in the post Colombian time of around 1550 were fighting a war for survival, but the biggest enemy was not the Spanish, it was disease. Measles, influenza, typhoid, yellow fever, and especially small pox decimated the population. Why was it though that the “European diseases” won over the local ones. Why didn’t the local germs decimate the conquistadors. Why wasn’t it the other way around? Was it because the population of the Americas had better sanitary practices? They didn’t live so densely packed? But even then, there must has been some endemic diseases the Europeans were not familiar with, why did the Old World diseases prevail agains the New World diseases?
From the FAQ:
/u/anthropology_nerd discusses European settlers being devastated by American disease, the impact that colonial systems and societal disruption had on indigenous mortality, and faulty interpretation of mortality figures here
/u/CommodoreCoCo critiques (by way of Jared Diamond) the geographic determinism baked into this premise, and gets into the historiography of the disease myth here
There is of course a lot more to be said, especially about the historiography of the narrative.