Why did the diseases European colonizers brought to the Americas kill off natives in huge numbers but not the other way around?

Question

Why didn’t diseases native to the Americas kill off European colonizers in large numbers?

In: Other

Answer 1

There is one example of a disease going the other way – Columbus [brought back syphillis](https://www.scientificamerican.com/article/case-closed-columbus/) from the Americas, and it did kill millions of Europeans.