Most communicable diseases have jumped from animal to man. Flu, pox, measles, colds all have jumped from cows, camels, horses, chickens and pig to humans. They have then jumped back and forth mutating with each jump. In Europe/Africa/Asia the human immune system adjusted to fight these diseases. In the Americas where the Neolithic revolution was plant rather then animal based this adjustment never occurred. Instead the American immune system adjusted to fight off what was the big threat in the Americas, parasites. Animal based communicable diseases killed off New Worlders in larger numbers then the parasites killed off Old Worlders because you normally don't catch parasites by casual contact.
STDs were something that were around world wide. No matter whe Both areas had their own versions but STDs traveled both ways. Syphilis is the biggest one that traveled to Europe which is why you hear about it the most.
It’s very strange that animals for the most part were never domesticated in the new world and that the wheel was never developed.