When I learned about European settlers from Spain, Portugal and the rest of Europe entering the New World (read: the Americas, my grasp of historical terms is poor), a main reason why I hear that they were able to conquer the native populations so quickly is the fact that they brought over diseases that the natives did not have natural immunities to and thus killed/weakened the natives enough to be conquered. My question is, were there such diseases of similar potency in the New World, and if so, why did that not then cripple the Europeans just as much as their diseases did the natives?
If I remember correctly, there was one instance of some settler bringing over syphilis or some other STD, but from what I understand, that was an isolated case.
Sorry in advance for incorrect terms, again.
If you go to the "Frequently Asked Questions" in the wiki for this site, under "Americas before Columbus and Native American History", you will find a section called Impact of indigenous diseases on the Europeans. That section has several good answers to this question because it gets asked fairly frequently. I recommend you look for entries by u/anthropology_nerd and u/400-rabbits.