Scientists revive ancient zombie virus from permafrost

While a pandemic caused by a disease from the distant past sounds like the plot of a sci-fi movie, scientists warn that the risks, while small, are underestimated. Chemical and radioactive waste from the Cold War, which could potentially harm wildlife and disrupt ecosystems, could also be released during thaws, CNN tells CNN.

“There’s a lot going on with permafrost that’s worrisome, and it really shows why it’s important that we keep as much of the permafrost frozen as possible,” explains Kimberly Miner, climate scientist at NASA’s Jet Propulsion Laboratory at the California Institute of Technology in Pasadena, Calif. ).

Permafrost covers a fifth of the Northern Hemisphere, supporting the arctic tundra and boreal forests of Alaska, Canada, and Russia for millennia. It serves as a kind of “time capsule” that contains – in addition to ancient viruses – the mummified remains of a number of extinct animals that scientists have been able to unearth and study in recent years, including two cubs of a cave lion and a woolly rhinoceros.

The reason permafrost is good storage is not just because it’s cold; it is an oxygen-free environment into which light does not penetrate. But current daytime temperatures in the Arctic are warming four times faster than the rest of the planet, weakening the region’s top layer of permafrost.

To better understand the risks associated with frozen viruses, Jean-Michel Claverie, professor emeritus of medicine and genomics at the Medical School of Aix-Marseille University in Marseille, France, tested soil samples taken from the Siberian permafrost to determine whether they contain viruses. the particles are still infectious. He’s looking for what he describes as “zombie viruses” – and found some of them.

Claverie is studying a particular type of virus he first discovered in 2003. Known as giant viruses, they are much larger than the normal variety and are visible under a normal light microscope rather than a more powerful electron microscope, making them a good model for this kind of laboratory work.

His efforts to detect viruses frozen in permafrost were partly inspired by a team of Russian scientists who, in 2012, revived a wild flower from 30,000-year-old seed tissue found in a squirrel’s burrow. (Scientists have since also successfully brought ancient microscopic animals back to life.)

In 2014, Professor Claveri managed to revive a virus he and his team had isolated from permafrost, making it infectious for the first time in 30,000 years by introducing it into cultured cells. For safety reasons, he decided to study a virus that could only infect single-celled amoebas, but not animals or humans.

He repeated the feat in 2015 by isolating a different type of virus that also targeted amoebas. And in their latest study, published Feb. 18 in the journal Viruses, Claveri and his team isolated multiple strains of the ancient virus from multiple permafrost samples taken from seven different locations across Siberia, and showed that each could infect cultivated amoeba cells.

These latest strains represent five new families of viruses, in addition to the two he revived earlier. The oldest of these was nearly 48,500 years old, based on radiocarbon dating of the soil, and came from a sample of earth taken from an underground lake 16 meters below the surface. The “youngest” samples found in the contents of the stomach and wool of the remains of a woolly mammoth are 27 thousand years old.

The fact that the viruses that infect amoebas are still contagious after such a long time is indicative of a potentially bigger problem, Claveri said. He fears that people regard his research as a scientific curiosity and do not perceive the prospect of the return of ancient viruses to life as a serious threat to public health.

“We look at these amoeba-infecting viruses as surrogates for every other possible virus that could be found in permafrost,” Claverie told CNN.

“We see traces of many, many, many other viruses,” he added. So we know they are there. We don’t know for sure that they are still alive. But our reasoning is that if amoeba viruses are still alive, then there is no reason why other viruses would not still be alive and able to infect their own hosts.”

Traces of viruses and bacteria have been found in the permafrost that can infect humans.

A lung sample from a woman’s body exhumed in 1997 from permafrost in a village on the Seward Peninsula in Alaska contained genomic material from the influenza strain responsible for the 1918 pandemic. In 2012, scientists confirmed that the 300-year-old mummified remains of a woman buried in Siberia contained the genetic signatures of the virus that causes smallpox.

An anthrax outbreak in Siberia that affected dozens of people and more than 2,000 reindeer between July and August 2016 has also been linked to deeper permafrost thaw during exceptionally hot summers, allowing old spores of Bacillus anthracis to float to the surface from old graves or animal carcasses.

Birgitta Evengaard, Professor Emeritus in the Department of Clinical Microbiology at Umeå University in Sweden, said there is a need to strengthen surveillance of the risk posed by potential pathogens from thawing permafrost, but cautioned against an alarmist approach.

“You have to remember that our immune defenses have evolved in close contact with the microbiological environment,” said Evengaard, who is part of the CLINF Nordic Center of Excellence, a group that investigates the impact of climate change on the prevalence of infectious diseases in humans and animals in northern regions.

“If there is a virus hidden in the permafrost that we haven’t come into contact with for thousands of years, it’s possible that our immune defenses aren’t strong enough,” she said. “The right thing to do is respect the situation and take the initiative, not just react. And the way to deal with fear is to have knowledge.”