You always hear how the Native Americans were killed by the millions because of foreign diseases, but you never hear about the same thing happening to the European settlers? Surely the Natives would have also had diseases their immune systems adapted to fight that the Europeans Had never encountered.
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Scroll down to: Impact of indigenous diseases on the Europeans
In short, yes, probably most famously syphilis, along with a host of various parasites. But unlike smallpox which can kill you days or maybe weeks after getting it, syphilis takes many years