Swords, Sails, and Smallpox: Were the Vikings History's Original Superspreaders?
Uncovering how Viking voyages may have spread one of history's deadliest diseases across continents.
The Viking Age (circa 793–1100 AD) conjures images of fierce warriors, swift longships, and legendary conquests. However, recent research suggests that the Norse may also have played an unexpected and sinister role in history: the spread of smallpox. Far beyond raiding and trading, the Vikings’ extensive travels may have helped disseminate one of the world's deadliest viruses, making them inadvertent superspreaders.
Unveiling the Smallpox Connection
Smallpox, caused by the variola virus, has long been one of humanity's most devastating diseases, claiming millions of lives before its eradication in 1980. While its origins remain murky, a groundbreaking 2020 study published in Sciences shed new light on its ancient history. Researchers analyzed DNA extracted from Viking-age human remains in Scandinavia and found evidence of an extinct strain of the variola virus. This discovery pushed the known existence of smallpox back over 1,400 years, suggesting that the disease ravaged populations much earlier than previously thought.
Crucially, the study highlighted the Vikings’ potential role as vectors. With their extensive maritime networks spanning Europe, the Middle East, and North America, the Vikings could have acted as biological conduits, carrying the virus far and wide.
Superspreaders Across Continents
The Vikings were uniquely positioned to spread diseases like smallpox. Their voyages were not isolated raids but formed an intricate web of interaction. They interacted with diverse populations and ecosystems by establishing trade routes and settlements. As seen in their expeditions to Constantinople, the British Isles, and Greenland, the Vikings were adept at crossing geographical and cultural boundaries.
One compelling hypothesis is that the crowded and unsanitary conditions aboard Viking longships created the perfect breeding ground for viruses like smallpox. Although the Vikings were known to carry cats on their ships to control rat populations—as I explored in my article on Viking maritime practices—this effort to reduce pests may not have been sufficient to prevent the spread of human-borne pathogens. The close quarters and prolonged exposure during voyages could have accelerated disease transmission among the crew, turning a single infected individual into a super-spreader.
Methodology Behind the Discovery
The discovery of smallpox in the Viking Age remains a result of groundbreaking advances in ancient DNA analysis. Researchers extracted DNA from the teeth and bones of human remains buried in sites across Scandinavia. By focusing on well-preserved samples, scientists could identify genetic traces of the variola virus, confirming its presence in Viking populations.
This study's use of high-throughput sequencing technologies is remarkable. These technologies allowed researchers to reconstruct ancient viral genomes with unprecedented precision. This approach confirmed the existence of smallpox during the Viking Age and revealed that the strains present at the time differed from the modern variola virus eradicated in the 20th century. These ancient strains likely caused milder outbreaks but contributed to the disease's long history of human affliction.
The study also employed radiocarbon dating to establish a timeline for the remains, aligning the presence of smallpox with the height of Viking activity. By correlating these findings with historical accounts and archaeological evidence, researchers were able to hypothesize how the Vikings' extensive travel networks facilitated the spread of the virus.
The Middle East Connection: Raiders Turned Traders
The Vikings’ expeditions extended well into the Middle East, where they established trade routes along the rivers of modern-day Russia and engaged with the Byzantine and Abbasid empires. These interactions may have exposed them to pathogens circulating in the densely populated urban centers of the Middle East. Rather than introducing smallpox to the region, it’s more plausible that the Vikings contracted the virus there and brought it back to Europe.
The return journey—often involving prolonged stops at trading hubs like Kyiv or Novgorod—would have allowed the virus to spread. The Vikings’ dual roles as traders and raiders further increased their contact with varied populations, amplifying the disease’s reach.
Evidence from the Grave
Archaeological discoveries support the theory of Viking-era smallpox transmission. The 2020 Science study found smallpox DNA in Viking-age skeletal remains from multiple locations, including Sweden, Norway, and Russia. These findings suggest that the disease was widespread among Norse populations and likely persisted over generations.
Further supporting this are historical accounts of disease outbreaks in medieval Europe. While records from the Viking Age are sparse, later chronicles, such as those from Anglo-Saxon England and Frankish Europe, describe plagues sweeping through regions frequented by the Norse. For example, the Anglo-Saxon Chronicle mentions pestilence in the 9th century, when Viking raids and settlements were prevalent. Similarly, Frankish annals recount outbreaks in territories impacted by Norse incursions, suggesting a correlation between Viking activity and the spread of disease. It’s reasonable to infer that their mobility played a role in introducing or exacerbating these outbreaks.
The Superspreader Framework
Modern epidemiology offers a valuable lens for understanding how the Vikings may have functioned as superspreaders. Key characteristics of superspreaders include high mobility, extensive contact networks, and prolonged infectious periods—all traits that align with Viking lifestyles. Their longships carried not just warriors and goods but also invisible pathogens, making every raid or trade mission a potential vector for disease.
Mitigating Factors: Hygiene and Cats
Despite their role in disease transmission, the Vikings were not oblivious to hygiene. Viking culture actively encouraged cleanliness. Historical sources, including Anglo-Saxon, Frankish, and Scandinavian accounts, describe Vikings bathing at least once a week—a practice notably more frequent than that of their southern European counterparts. Archaeological finds of daily life, including intricately designed grooming kits with combs, ear picks, and tweezers, further emphasize personal grooming. Current scholarship often regards the Norse as being as clean, if not cleaner, than other Europeans of the time. This commitment to hygiene may have been partially practical, as it could enhance social interactions and reduce lice and other parasitic infestations common in medieval societies.
As noted earlier, their use of cats on ships to control rats demonstrates a rudimentary understanding of pest management. This practice likely reduced the risk of rat-borne diseases like the bubonic plague, which spread via fleas. However, smallpox—a human-specific virus transmitted through respiratory droplets or direct contact—would not have been mitigated by such measures.
Lessons for Today
The Viking example underscores the profound impact of human mobility on disease dynamics. Much like modern air travel enables the rapid global spread of pathogens, the Vikings’ maritime networks connected distant regions, facilitating the exchange of both goods and germs. Understanding their role as superspreaders provides valuable historical context for pandemics and highlights the interconnectedness of human societies.
Conclusion: The Legacy of Viking Voyages
While the Vikings are celebrated for their adventurous spirit and cultural contributions, their legacy also includes the unintended consequences of their mobility. The discovery of smallpox DNA in Viking-age remains challenges us to reconsider their historical impact, not just as conquerors and traders but also as carriers of one of history’s deadliest diseases.
When I first wrote In The Shadow of the Beast (Saga of Hasting the Avenger, Book 2), I wanted to explore the external adventures of Hasting and his crew and the unintended consequences of their far-reaching voyages. In the book, Hasting’s settlement is devastated by a plague they unwittingly bring back from distant lands, a narrative decision born from my curiosity about the hidden costs of exploration. Reading studies like the one that uncovered smallpox DNA in Viking-age remains validates this storytelling choice in a way I never expected. It’s fascinating—and sobering—how these historical findings align with the fictional world I created. The idea that Vikings could act as unwitting carriers of disease reinforces the complexity of their legacy, and it makes me reflect on how fiction can sometimes intuitively echo historical truths long before they’re fully uncovered. It’s a reminder of why I love weaving history and imagination together—there’s always more beneath the surface.
By exploring how the Vikings may have helped spread smallpox, we gain a deeper appreciation for the complex interplay between human activity and disease. Whether through their longships, trade routes, or interactions with Indigenous peoples, the Norse left an indelible mark on the world that extends beyond swords and sagas to the microscopic agents of history.
Here are citations for the genetic studies on smallpox and Vikings:
Smallpox in Viking DNA
Mühlemann, Barbara, et al. "Ancient Variola Virus Genomes Reveal the Origins and Evolution of Smallpox." Science, vol. 369, no. 6502, 2020, pp. 86–91.
DOI: 10.1126/science.aaw8974This study identified ancient strains of smallpox in Viking-age human remains, suggesting the disease was widespread in their populations.
Press Coverage on Viking Smallpox
St. John’s College, Cambridge: "Vikings Had Smallpox and May Have Helped Spread the World’s Deadliest Virus." https://www.joh.cam.ac.uk/vikings-had-smallpox-and-may-have-helped-spread-worlds-deadliest-virus
ScienceDaily: "Smallpox May Have Plagued Humans Earlier Than Thought." https://www.sciencedaily.com/releases/2020/07/200723143733.htm
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