Why Didn't Europeans Suffer from American or Aboriginal Plagues?

by Haylettc

So, this week I was reading about the decimation of the Australian Aboriginal population partially through disease and I was suddenly struck with a question that seems kind of obvious, but which I'd never considered before.

What was it about the "mainland" continent that made diseases from Europe massively devastating to the people of the Americas (and Aboriginals and others), while no diseases were brought back to Europe which really wreaked any havoc?

Given that Europeans would have been just as unexposed to American diseases as Native Americans were to European diseases, why was the resultant devastation so different? I've read a decent bit about American history at this point and know that it's popularly believed that 80-90% of Native Americans were wiped out by plague.

It just doesn't make sense that there wouldn't even be a ripple of something similar in Europe as Natives were taken back as slaves and Europeans returned from abroad. What am I missing?

Edit: Parentheses portion added

Darzin_

More can be always be said but this answer by u/anthropology_nerd and this answer by u/400-Rabbits should help give you some idea. One factor not mentioned by them is that some of the diseases Europeans brought came from domesticated livestock and that may have accounted for some of the disparity.