Scientists show that a variant of the smallpox virus was widespread among Vikings.
Smallpox is a life-threatening disease caused by a virus from the Variola genus . The virus is highly contagious, killing about a third of the people infected by it. And the people who survived a virus infection often suffered permanent damage. They went blind or were covered with obvious scars; left by the characteristic vesicles that formed on the skin after infection. It is estimated that the smallpox virus claimed more than 300 million (!) Victims in the twentieth century alone. Fortunately, the disease no longer occurs today; a worldwide vaccination campaign was launched in the 1970s, and not long after, the viral disease became known as the first virus to be eradicated by humans.
When the smallpox virus – which probably passed from animals to humans – first affected humanity, it is unclear to this day. Historians suspect that it is a very old disease, which may have been around 10,000 years before Christ. They rely, among other things, on written sources that describe diseases and symptoms reminiscent of smallpox. But hard evidence – in the form of thousands of years old human remains that testify to the disease – is lacking. The oldest evidence convincingly demonstrating that the virus affected humans is from the seventeenth century.
However, a new study now shows that the virus had been circulating long before. And this among Vikings, who lived about 1400 years ago. And thus, the new evidence for the disease is about 1,000 years older than the oldest evidence we knew until recently.
The researchers base their conclusions on an analysis of the remains of 1,867 people who lived between 31,000 and 150 years ago. In particular, they searched for genetic material from Variola viruses. “We start with human remains – often a tooth – and grind them, then extract DNA from them,” explains researcher Martin Sikora to Scientias.nlfrom. “Most of this DNA consists of a mix of molecules from the individual and microbial DNA from the earth in which the individual was located. If an individual was infected with a pathogen that was still circulating in the bloodstream at the time of death, then a small portion of the total DNA we extracted from the remains will come from the genome of this pathogen. ” Genetic material from a Variola virus was found in thirteen of the individuals studied. And no less than eleven of the thirteen individuals belonged to the Vikings.
The Variola virus that these Vikings had among its members is not identical to the virus that was eradicated in the twentieth century. “We found that the virus is closely related to the virus strains from the last pandemic,” said Sikora. “But there are also genetic differences. If we compare the entire genome of the viruses, we see that they differ 1 to 2 percent from each other, that is, 1 to 2 differences appear per 100 base pairs. ” The virus should not be seen as an ancestor of the smallpox virus that later killed millions of people. Instead, they share a common ancestor that occurred about 1,700 years ago. The strains that caused a deadly pandemic show some unique genetic changes that we don’t see in the Viking era tribes. ”
The symptoms of the Vikings
It is difficult to say exactly how the smallpox variant that occurred among the Vikings manifested itself. “Of course we have not found any direct evidence for the symptoms of the disease, but we can make some predictions based on a comparison between the reconstructed genome and the genome of modern smallpox viruses,” says Sikora. For example, the virus that ravaged the Vikings shows a gene that we also see in the modern smallpox virus and that is associated with high fever. “It suggests that high fever was also a symptom of the disease in Vikings’ time.” In addition, it seems not inconceivable that some Vikings actually succumbed to the virus; the Vikings studied in which viral DNA was found must have had the virus in their blood at the time of death.
Although the virus has only been found in eleven Vikings, Sikora and colleagues conclude that it must have been widespread. “We found evidence for the virus in eleven out of 500 individuals from the same time and region who were analyzed by us,” said Sikora. This means that about 2 percent of the studied individuals have come into contact with the virus. In reality, that percentage is undoubtedly much higher, says Sikora. For example, researchers can only detect the viral DNA 1400 years after data if people have the virus in the bloodstream at the time of death. There must also be a lot of viral DNA in the blood for the virus to be detected. And finally, the DNA must also have been well preserved.
“JUST AS PEOPLE WHO TRAVEL AROUND THE WORLD TODAY ARE SPREADING COVID-19 QUICKLY, IT IS LIKELY THAT THE VIKINGS SPREAD THE SMALLPOX”
And if the virus was widespread among Vikings, they must have spread it throughout Europe during their travels. “We already knew the Vikings were traveling through Europe and beyond and now we know they had smallpox,” said researcher Eske Willerslev. “Just as people who travel around the world today are spreading COVID-19 quickly, it is likely that the Vikings spread the smallpox.”
The research provides more insight into the evolution of the Variola viruses. “There are several ways in which viruses diverge and mutate into milder or more dangerous strains of viruses,” said researcher Barbara Mühlemann. “This (research, ed.) Provides significantly more insight into the steps taken by the Variola virus during its evolution.”
And that’s not only helpful for a better understanding of the past, but can also come in handy in the future. “By studying these ancient viruses, we can learn more about strains of virus that were once able to infect humans and build a catalog containing the genetic changes that contributed to the spread and severity of the disease. In addition, our study demonstrates once again that viruses from animals affected human populations throughout history – and much earlier than previously thought – and that the current coronavirus outbreak is just another example. We would consider other smallpox viruses currently circulating in a wide variety of animals – take the Monkeypox virus, for example– must monitor closely. And thanks to our research, we’ve now got a first glimpse of the genetic changes we need to look out for. ”