Pretty much as the title - when the Spaniards and other Europeans showed up in the 16th century the effect was pretty catastrophic on native populations as diseases like smallpox spread like wildfire among a population with no immunity to it.
But why when Leif Erikson and his Vikings rocked up a few hundred years earlier did this not happen to the ‘skraeling’ populations of Greenland and Vinland? Was contact just too brief, did the Norsemen not carry as contagious diseases, or what?
I put the following words into Google (with no quotation marks but in this order):
> Why didn’t the Norse infect native Americans with disease?
and got a lot of webpages claiming to know why this was true.
The Norse didn’t land in a very populated or well-connected area of the continent. Even if every native who came within 50m of one of them instantly caught a deadly disease, it is unlikely that it would have spread beyond Newfoundland.
Nor did the Norse really seek out contact with the natives. Maybe some light trading, but not the prolonged contact that would really help disease to spread.
From skimming through those pages I think the best answer is no one knows. Any evidence the Norsemen infected the natives would be very thin at best. The Spanish stayed and chronicled the spread of infectious agents, the Norse died out. The Norse may not have had any contact with the natives, Newfoundland was pretty sparsely population back then. The Norsemen may well have been free of any infectious diseases, having been isolated on Iceland, then isolated on Greenland. Also, we have 500 years of mutations between contacts, perhaps the natives were hit hard by the 1000 AD small pox, recovered, only to get zapped again with 1500 AD small pox … except the 1500 AD small pox came in massive numbers comparatively.
Evidence that the Norsemen were even here is thin, can’t imagine evidence of a pandemic would survive 1,000 years … so no one really knows.
I think the answer that has the most plausibility is that the Norse explorers who travelled to Vinland were already from a small, isolated population - the Norse who lived in Greenland. Epidemic diseases do not linger in small, isolated populations - they flame through them and are gone.
Moreover, the Norse encountered the natives who lived in what is now Newfoundland and Labrador - who lived in small, hunter-gatherer communities. The Spanish, in contrast, encountered massive urban settlements in Mesoamerica, having come more or less directly from Spain (with perhaps a stopover in Cuba).
So, there was no direct contact between the mass of European population (a reservoir for epidemic diseases) and the mass of native American population (another such reservoir). Instead, there was contact - fairly short term contact - between one isolated population of Europeans and another isolated population of native Americans.
This dramatically lowered the chance for epidemic disease transmission.
Virtually of the major pandemic diseases are born in tropical areas. The carriers don’t do well in the cold north. Spain is semi-tropical and had long contact with Africa. It’s likely that the Norse never had serious infections with these illnesses. They did travel widely but seldom created colonies. The ones in Canada yielded mostly battles rather than intermixing. The Norse stayed almost exclusively on islands off the Canadian coast. A few travelers may have hit the mainland but that wouldn’t be enough.
So the OP’s answers are the right ones. The two situations are wildly different from one another.
Wasn’t that contact also more along the lines of vicious combat, rather than peaceful trade?
I’d imagine that there’s not as much disease transmission under those circumstances than if you were trading and peacefully coexisting.
The Norse were present in Newfoundland for many years - evidence at L’Anse aux Meadows spans decades, IIRC. They eventually left the area, whether through choice or attrition is not clear. But implying that the Spanish were here long enough to see the effects of their presence but the Norse just popped in and out (or off) is not correct.
They also had recorded contact with the “skraelings” and it’s almost inconceivable that they had anything but regular (if possibly wary and infrequent) contact with the natives during their time in North America.
But the other answers in this thread pretty much answer the question, even if a little loose and vaguely.
I’m not sure I’d describe what the Spanish did as “peacefully coexisting” ( 
), but yes, there is no doubt that they had a lot more contact with the locals than the Norse did - but then, we don’t really know how much contact the Norse actually had. Only a limited amount was written about their settlement, which tended to focus on the fighting, but that may not have been the whole story.
I also learned in a university history course that the difference between Norse technology and Skraeling technology, at that time, was such that the Skraelings could hold their own.
Another thing that I learned was that Vikings tended not to conquer and occupy but, instead, did “hit and runs (while doing maximum damage)” and that, when they stayed, tended to become assimilated.
I also believe that the fact that Viking explorations and attacks did not represent a single coordinated effort by a nation-state may have had something to do with it.
Smallpox was endemic in Europe by the time the Spanish arrived in America. The Vikings came to America much earlier. Was smallpox commonly found in Vikings at that time in Northern Europe?
From what I can find, smallpox wasn’t well established in Europe before the time of the Crusades but was sporadic due to low population density. It would probably not have been endemic in Scandinavia, and even less likely to be transferred on the long ocean voyage to Greenland and then on to North America.
As has been said, the main reason that the Norse voyages to North America didn’t spread epidemic diseases to the New World was low population density in both the colonizing population and in the areas that they contacted. Epidemic disease can’t maintain itself and spread under such conditions. There may have been some mortality in local native populations that were in contact, but the diseases wouldn’t have spread much beyond that.
Moderator Note
This is not a useful response. Per GQ rules, we ask that posters not respond to questions with replies such as “just Google it.” No warning issued, but let’s refrain from this kind of reply in the future.
Colibri
General Questions Moderator
Did the Norse bring any animals with them to the new world? From what I understand pigs can transmit disease. If there were no animal vectors of transmission then that would also lower the chance of infecting the locals.
Based on excavations of farms in Greenland, they had cattle, sheep, goats, and pigs.
AFAICR, the excavations have not turned up evidence of domesticated animals at L’Anse aux Meadows. If they had intended on establishing permanent settlements, they would have brought some over at some point. (Absence of evidence is not evidence of absence, so take that for what it is worth.)
While lots of human diseases originate in farm animals, I don’t think that contact with animals presents a very big risk of catching a disease. Farmers just spend so much time in close quarters with their animals that the risk becomes significant.
Once the virus has jumped to humans, you are much more likely to catch it from another human than the original animal.
Actually, there is some evidence that the Norse from Greenland sought out natives. There is a site on Baffin Island named Tanfield Valley which was probably a Norse trading post. There’s a couple other places, one in northern Labrador, which could also be trading posts, but they haven’t been excavated yet.
There’s a second site in Newfoundland, Point Rosee, which is in the south of the island, which may have also been a Norse settlement.
However, none of these would change the answers given above.
Tenochitlan (Mexico City) was already a major urban metropolis when the Spanish arrived. Certainly the spread of disease and massive die-offs of major percentages of the population didn’t help with the existing social, economic, and political issues that any major metropolis has, so they were pretty much doomed from the start. Certainly the Spanish were more than happy to take over the failing, massively dysfunctional government and run things the way they thought would be best. As we know, the Europeans managed to wreck the ecosystem pretty quickly..
You are right about the assimilation. The Vikings had major colonies in England (Danelaw), northern France (Normandy), Sicily, Kiev, Scotland, and several other places, but Scandinavian languages have not survived in any of those areas and the local people today do not generally consider themselves Scandinavian - rather, the Vikings seem to have set themselves up as rulers and then learned the local language.
When a conquering population assimilates to the local language and/or culture, that’s usually a sign that the conquerors do not have enough social clout to get everyone else to change - quite likely an indication that their numbers were in fact small relative to the conquered population.
France has been a hotbed of assimilated conquerors for a while now - not only the Vikings but later the German Franks (who gave France its name) gave up their language upon arrival. C’est la vie.
It is interesting to consider that perhaps the native cultures of the new world would have been better off if the Vikings had brought the whole range of European epidemic diseases over - they may have developed some immunity by the time the Spanish etc. arrived.