Not to discourage further contributions, but this (very interesting!) question has been asked a few times before and has received some really solid answers:

In this previous thread, u/anthropology_nerd and u/prehensilefoot address a similar, if not identical, question. Prehensilefoot's answer specifically mentions syphilis as the most obvious example of Europeans contracting diseases from the New World.

u/400-Rabbits also gave a fascinating answer, arguing that Europeans contracted diseases as well.

For future reference, I found these answers through the AskHistorians FAQ, which is super helpful (if not always straightforward) for a lot of questions!