system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How come indigenous people have historically been affected by invaders diseases but the invaders weren't affected by some random disease that the natives had?
gpt
It's not always one way. Syphilis was one example of a new world disease that was definitely problematic for Europeans.  
But often times the larger populations of more developed nations meant that there were larger infection pools, over time only the most infectious of diseases would be able to propagate.   
Also many of the Europeans at the time lived in close proximity to livestock, meaning they learned to live with more diseases that could jump species.