How prevalent was smallpox among the Norse in Northern Scandinavia, Iceland, & Greenland?

Question

The Norse are the only people that - we can verify today - had pre-columbian contact with the New World. While it's clear that their settlements didn't last, it does appear that they interacted with the native people of North America. What I find interesting (and bit puzzling) is that their contact did not result in the spread of smallpox or other infectious diseases that, in post-columbian contact, led to the deaths of millions of Amerindians.

In order to answer the question above I thought it would be important to know how prevalent smallpox (or any other diseases that Amerindians succumbed to) were among the Vikings around the year 1000 A.D.? Are there records of plagues around that time period or other indications that the Norse were equally as likely to carry smallpox as say the Spanish?

Answer 1

Infectious diseases require a certain critical mass of people to become endemic in a population. Smaller than that, and they burn themselves out by making every susceptible person either immune or dead. The smaller and more isolated the population, the more quickly this happens.

Based on what I'm seeing in Epidemics and Pandemics: Their Impacts on Human History, Iceland appears to be below this threshold for Smallpox. It had an outbreak in 1670, and then a generation later (1707) another carried over from Denmark.

To get from there to the Americas, it would also have to jump from there to Greenland in the short window (roughly 2 years it appears from the records) that its floating around Iceland, and then from there to the mainland, and again from there to the Inuit populations. Inuit did not live in big settlements, so it would have to somehow then get transmitted from small hunting tribe to tribe many times over, crossing several more cultural gradients, until it hit a large city-dwelling culture further south to become endemic in.

I've seen multiple claims that Smallpox hit the Greenland settlement in the early 1400's. The Greatest Killer: Smallpox in History by Donald R. Hopkins for example. I'm not sure what those claims are based on¹. This would be right around the end of that settlement, which by chronology alone would strongly imply the disease was a factor in its demise.²

^{1 - Anyone?}

^{2 - You could also, purely by this chronology, postulate that this may in fact be what caused the end of the classic ("middle") Mississippians. I'd need to see some actual evidence before thinking this leap reasonable though.}

Answer 2

Many deadly diseases appeared late in Scandinavia; for example, the first recorded smallpox epidemic (variola) in Iceland was in 1241, arriving via the area of Denmark. Smallpox wasn't really a severe problem in Europe until the start of the Crusades (just at the end of the Viking Age), when returning crusaders brought the disease home with them. ("The History of Smallpox and its Spread Around the World". Ch. 5. Smallpox and its Eradication. Eds. Frank Fenner, Donald A. Henderson, Isao Arita, Zdeněk Ježek and Ivan Danilovich Ladnya. Geneva: World Health Organization. pp. 209-244. http://whqlibdoc.who.int/smallpox/9241561106.pdf)

Similarly, typhus ("spotted fever", Rickettsia prowazekii) doesn't seem to have spread throughout Europe until 1489, when Spanish soldiers who fought the Turks in Cyprus brought the disease to Spain. (James G. Olson. Epidemic Typhus: A Forgotten But Lingering Threat". Ch. 5. Emerging Infections 3. Eds. W.M. Scheld, W.A. Craig, and J.M. Hughes. Washington D.C.: ASM Press. 1999. pp. 67-72.)

Cholera is believed to have originated in the subcontinent of India. The disease may have been described by the Greek physician Hippocrates (460-377 BC), but the great cholera pandemics didn't occur until the 19th c. (Antonis A. Kousoulis. "Etymology of Cholera". Emerg Infect Dis. March 2012).

Prior to the scientific understanding of bacteria, and illness that could spread amongst people or animals could be considered "a plague". Hard evidence as to what diseases may have infected people in Viking Age Scandinavia are spotty. Tuberculosis, endemic in bovine populations, can be shown to have affected both humans and livestock in Viking Age Scandinavian settlements via the evidence of bone lesions.

Leprosy probably spread to Scandinavia during the Viking Age, when large numbers of slaves from Ireland were imported. Leprosy was known in Ireland as early as the 7th c. and widespread in Ireland by the 10th c. Certainly, both the Gulaþing Law and Borgarþing Law state that "a promise of marriage is not binding if one of the partners was found to be leprous". (Thomas M. Vogelsang. "Leprosy in Norway". Medical History 9:1 (Jan. 1965). pp 29-35. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1033440/pdf/medhist00156-0037.pdf)