It seems to be well-documented that European colonists (and African slaves) brought with them a number of Euroasian diseases that spread among the Native populations of the Americas and decimated them.
However, are there any recorded instances of diseases endemic to the Americas that the colonists caught (and lacked immunity to) and spread in Europe/Asia/Africa? If not, how come?
This is a huge subject and thus new contributions would be welcome. But there is a good section of the AH wiki that has a subject heading of Impact of indigenous diseases on the Europeans and should address a lot of your question. I recommend entries by u/anthropology_nerd.