Not an answer, but I've also always wondered why Native American's didn't have their own set of diseases that the European's immune systems were not prepared for.
There's always room for discussion, but perhaps these topics from the Native Americans and (European) Diseases section of our FAQ will answer your inquiry.
As a corollary: Do we actually know for sure that the Norse didn't provide an initial source of disease before the Europeans showed up and made the situation worse by spreading more diseases even further?
It seems plausible that there could have been multiple waves of pandemic, but I'm not sure what evidence we have for or against.
I had heard that there actually was a massive plague that decimated a majority of the North American Native populace prior to the arrival of the Europeans, which went a long way towards aiding their conquest of the continent. Didn't the natives already have their own dangerous diseases affecting them?
The areas Norseman went to where more sparsely populated.
Introduction of disease had nothing to do with how "utterly victorious" the europeans were. As a matter of fact, it took centuries after the first europeans brought the disease before europeans could completely subdue the americas. And the americas were subdued by guns rather than disease.
For example, even after 150 years after british invasion of north america, the best the colonists and the might british empire could do was to negotiate the appalachian mountains as the border between the colonies and the indians. So the colonists were relegated to a small sliver of the eastern seaboard while the natives controlled everything else. So that's how "utterly victorious", the colonies and the british empire was nearly 300 years after columbus.
https://en.wikipedia.org/wiki/Royal_Proclamation_of_1763
And it wasn't until decades later that the US pushed the "border" between indians and americans to the mississippi and started shipping indians west of the mississippi.
https://history.state.gov/milestones/1830-1860/indian-treaties
https://en.wikipedia.org/wiki/Treaty_of_Dancing_Rabbit_Creek
And it wasn't until after the civil war ended that the west was "won".
There have been countless wars with the natives from early 1600s and onwards.
https://en.wikipedia.org/wiki/American_Indian_Wars
It wasn't like the white man showed up and the indians died off.
The true "victory" didn't really come until well after the civil war when extraordinarily population growth along with advances in weaponry coupled with the railroad system allowed for the complete annihilation of the natives.
Even into the early 1800s, the natives were able to keep the white man at bay, but the industrial revolution, population growth, advances in weaponry, etc in the following decades tipped the scales in favor of the white settlers over the natives and the natives got wiped out ( not by disease but by the gun ).
White man's disease didn't wipe out the natives. No matter how hard it is to accept, it was the white man. Just like disease didn't wipe out the europeans, disease didn't wipe out the natives either. It was a rather prolonged unofficial genocide campaign. We wanted their land and they were simply too weak to stop us from taking it. Simple as that.
Edit: Downvoted for stating historical facts, treaties, etc? Welcome to reddit I guess...
There is one disease which many speculate was contracted by the early European explorers to the Americas: SYPHILIS. I've read a number of articles theorizing that syphilis was brought back to Europe from the new world (here's a Scientific American article about it), but most of these theories seem based solely on the timing of the first recorded syphilis outbreaks. Other than looking back at the history of the first outbreaks, I don't know that there would be any way to conclusively prove that syphilis came from America.
Syphilis is interesting, because it's closest cousins (also caused by treponemal bacteria) Yaws and Pinta, are typically tropical diseases (Here's a map of yaws endemic distribution from a Lancet article). As such, given our understanding of the areas touched by Norse visitors, it's unlikely that they would have encountered the early syphilis progenitor bacteria.
*Edit: I forgot words and things
What way would there be for us to reliably know whether or not there were any epidemics or breakouts of disease after the Norsemen left? It seems to me that primary native sources would be lacking after the hundreds of years until Europeans made contact with any other native group ever again, plus that so much could have changed anyways where it would have been impossible to know ever anyways.
