• Last week /u/sagathain summarized the current academic consensus on the topic in conjunction with the recent 'discovery' of possibly pre-Columbian allusion to the Old Norse place name in: Did Italian sailors really know about the existence of America 150 years before Columbus, as a slew of recent articles claim?
• The classic account of the settlement and abandonment of Vinland is found in: What stopped the viking colonization of america? by /u/textandtrowel
• My hypothetical explanation on 'Why didn't they...?' is also posted before in: Why didn’t the Vikings further colonize Vinland and why did they leave?

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As for 'Vinland and the disease transmission' topic, the following cut & paste from the similar question thread as OP posted today, Why didn't Norse Explorers Introduce 'Old World' Diseases to Indigenous Americans?, might be useful.

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While there is always more to be said on the topic, the basic outline that I summarized before in Were any diseases brought to America by the Vikings? is still valid (though a recent scientific article published since my linked post (Ledger, Girdland-Fink & Forbes 2019) suggests that the Norse people might sometimes take a visit in L'Anse aux Mewdows in course of the 11th century).

In short, the degree of contact between the Norse people and the indigenous people must have been very limited (if any), so it is not so unnatural to suppose that the pathogens that the Norse people had had did not transmitted to the indigenous people if they really met in the 11th century and later.

Additional References:

• Kuitems, M., Wallace, B.L., Lindsay, C. et al. "Evidence for European presence in the Americas in ad 1021." Nature (2021). https://doi.org/10.1038/s41586-021-03972-8
• Ledger, Paul M., Linus Girdland-Flink, Véronique Forbes. "New horizons at L’Anse aux Meadows." Proceedings of the National Academy of Sciences Jul 2019, 116 (31) 15341-15343; DOI: 10.1073/pnas.1907986116

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On the other hand, /u/anthropology_nerd who authored excellent answers to the following relevant question threads might also have something to say especially in the latter part of OP's question, from different point of view from mine:

• At what point did Native American groups acquire some kind of immunity to western diseases?
• One of the main reasons Europeans were so utterly victorious against Native Americans was the introduction of diseases, that decimated the population. Why did the Norsemen of Vinland not bring diseases that carried the same effect?