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Vikings had smallpox and may have helped spread the world’s deadliest virus
Smallpox spread from person to person via infectious droplets, killed around a third of sufferers and left another third permanently scarred or blind. Around 300 million people died from it in the 20th century alone before it was officially eradicated in 1980 through a global vaccination effort – the first human disease to be wiped out.
Vikings had smallpox and may have helped spread the world’s deadliest virus. Photo: Steinar Engeland/Unsplash
Now an international team of scientists have sequenced the genomes of newly discovered strains of the killer virus after it was extracted from the teeth of Viking skeletons from sites across northern Europe.
“We already knew Vikings were moving around Europe and beyond, and we now know they had smallpox. Just as people travelling around the world today quickly spread COVID-19, it is likely Vikings spread smallpox. Only back then, they travelled by ship rather than plane,” said Professor Eske Willerslev in the University of Cambridge’s Department of Zoology and St. John’s College.
The team found smallpox - caused by the variola virus - in 11 Viking-era burial sites in Denmark, Norway, Russia, and the UK. They also found it in multiple human remains from Öland, an island off the east coast of Sweden with a long history of trade.
They were able to reconstruct near-complete variola virus genomes for four of the samples. The genetic structure of this earliest-known smallpox strain is different to the modern smallpox virus eradicated in the 20th century.
Historians believe smallpox may have existed since 10,000 BC but until now there was no scientific proof that the virus was present before the 17th century. It is not known how it first infected humans but, like COVID-19, it is believed to be a zoonotic disease - one that originated in an animal.
While it is not clear whether these ancient strains of smallpox were fatal, the Vikings must have died with smallpox in their bloodstream for the scientists to detect it up to 1400 years later. It is also highly probable there were epidemics earlier than these findings.
“While written accounts of disease are often ambiguous, our findings push the date of the confirmed existence of smallpox back by a thousand years,” said Dr Terry Jones at the Centre for Pathogen Evolution at the University of Cambridge.
He added: “To find smallpox so genetically different in Vikings is truly remarkable. No one expected that these smallpox strains existed. It has long been believed that smallpox was in Western and Southern Europe regularly by 600 AD, around the beginning of our samples. We have proved that smallpox was also widespread in Northern Europe. Returning crusaders or other later events have been thought to have first brought smallpox to Europe, but such theories cannot be correct.”
“Smallpox was eradicated, but another strain could spill over from the animal reservoir tomorrow. What we know in 2020 about viruses and pathogens that affect humans today is just a small snapshot of what has plagued humans historically,” said Willerslev. (University of Cambridge)
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