‘Zombie’ virus spent 48,500 years in permafrost: scientists

Warmer temperatures in the Arctic are freezing permafrost of the region — the frozen layer of soil below the ground — and potentially reactivating viruses that, after lying dormant for tens of thousands of years, can threaten animal and human health.

While an epidemic caused by a disease from the distant past sounds like something out of a science fiction movie, scientists warn that the risks, while low, are underestimated. Chemical and radioactive waste dating back to the Cold War, which can harm wildlife and disrupt ecosystems, could also be released during the meltdown.

“There’s a lot going on with the permafrost that’s concerning, and (it) really shows why it’s so important that we keep as much ice as possible,” said a climatologist at NASA’s Jet Propulsion Laboratory. Kimberly Miner. at the California Institute of Technology in Pasadena, California.

Permafrost covers one-fifth of the Northern Hemisphere, underpinning Arctic tundra and mountain forests in Alaska, Canada and Russia for millennia. It serves as a kind of time capsule, preserving, in addition to ancient viruses, the mummified remains of a number of extinct animals that scientists have been able to discover and study in recent years, including: two cave lions cubs and a woolly rhinoceros.

The reason that permafrost is a good storage medium isn’t just because it’s cold; it is an oxygen-free environment where light does not penetrate. But current Arctic temperatures are warming up to four times faster than the rest of the planetweakening the upper layer of permafrost in the region.

To better understand the risks posed by 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 see if viral particles were present. contained in it are still infectious. He’s looking for what he describes as “zombie viruses,” and he’s found some.

VIRUS HUNTER

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

His efforts to detect viruses frozen in permafrost were partly inspired by a group of Russian scientists who in 2012 resurrected a wildflower from 30,000-year-old seed tissue found in a squirrel hole. (Since then, scientists have also successfully brought ancient microscopic animals have come back to life.)

He succeeded in 2014 revive the virus that he and his team isolated from the permafrost, Making it infectious for the first time in 30,000 years by introducing it into cultured cells. To be safe, he chose to study a virus that could only target single-celled amoebae, not animals or humans.

He repeated the feat in 2015. isolation of different types of virus which also targeted amoebae. And in his latest research. published February 18 in the journal VirusesClaveri and his team isolated several strains of the ancient virus from multiple permafrost samples taken from seven different sites in Siberia and showed that they could infect cultured amoeba cells.

Those latest strains represent five new virus families, in addition to the two he had previously revived. The oldest was nearly 48,500 years old, based on radiocarbon dating of the soil, and came from a soil sample taken from an underground lake 16 meters (52 feet) below the earth’s surface. The youngest specimens found in the stomach contents and coat of woolly mammoth remains were 27,000 years old.

That the viruses that infect the amoeba are still infectious after so long is indicative of a potentially larger problem, Clavery said. He is afraid that people will see his research as a scientific curiosity and will not perceive the prospect of ancient viruses coming back to life as a serious threat to public health.

“We’re looking at these amoeba-infecting viruses as surrogates for all the possible viruses that might be in the permafrost,” Claveri told CNN.

“We see traces of many, many, many other viruses,” he added. “So we know they’re out there. We don’t know for sure that they are still alive. But our reasoning is that if amoeba viruses are still alive, there’s no reason other viruses shouldn’t still be alive and capable. to infect their hosts.”

PREVENTION OF HUMAN INFECTION

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

a Lung sample from a woman exhumed from permafrost in 1997 A village on Alaska’s Seward Peninsula contained genomic material from the strain of influenza responsible for the 1918 pandemic. In 2012, scientists confirmed 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 dozens of people and more than 2,000 reindeer were affected July-August 2016 is also associated with deeper melting of permafrost during exceptionally hot summers. allowing old spores of Bacillus anthracis to reappear from old graves or animal corpses.

Birgitta Evengaard, professor emeritus of the Department of Clinical Microbiology at Umeå University in Sweden, said better control of the risk of potential pathogens during permafrost thawing was needed, but warned against an alarmist approach.

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

“If there’s a virus lurking in the permafrost that we haven’t come into contact with for thousands of years, it could be that our immune defenses aren’t good enough,” he said. “It is right to show respect for the situation and to be proactive and not just reactive. And the way to fight against fear is to have knowledge.”

POSSIBILITIES OF VIRAL TRANSMISSION

Of course, in the real world, scientists don’t know how long these viruses can remain infectious after being exposed to current conditions, or how likely the virus is to encounter a suitable host. Not all viruses are pathogens that can cause disease. some are benign or even beneficial to their hosts. And although 3.6 million people live there, the Arctic is still a sparsely populated place, making the risk of human exposure to ancient viruses very low.

However, “the risk should increase in the context of global warming,” Clavery said, “where the melting of permafrost will continue to accelerate and more people will populate the Arctic as a result of industrialization.”

And Clavery is not alone in warning that the region could become fertile ground for a spillover event, when the virus jumps to a new host and begins to spread.

Last year, the team of scientists published research on soil and lake sediment samples taken from Hazen Lake, a Canadian freshwater lake located in the Arctic Circle. They sequenced the sediment’s genetic material to identify viral signatures and the genomes of potential hosts, plants and animals, in the area.

Using computer model analysis, they hypothesized that the risk of viruses spreading to new hosts is greater in areas with large amounts of glacial meltwater flowing into the lake, a scenario that is becoming more likely as the climate warms.

UNKNOWN CONSEQUENCES

Identifying the viruses and other hazards contained in the warming permafrost is the first step in understanding the threat they pose to the Arctic, said a miner at NASA’s Jet Propulsion Laboratory. Other challenges include quantifying where, when, how fast, and how deeply the permafrost will melt.

Melting can be a gradual process, as little as centimeters per decade, but it can also happen more quickly, such as with massive landslides that can suddenly expose deep and ancient layers of permafrost. The process also releases methane and carbon dioxide into the atmosphere, an overlooked and underestimated driver of climate change.

Miner listed a number of potential hazards currently frozen in the Arctic permafrost in 2021. The article was published in the scientific journal Nature Climate Change.

Those potential hazards included buried mining wastes of heavy metals and chemicals such as the pesticide DDT, which was banned in the early 2000s. Radioactive materials have also been dumped into the Arctic by Russia and the United States since the advent of nuclear testing in the 1950s.

“Abrupt melting rapidly exposes old permafrost horizons, releasing compounds and microorganisms that are sequestered in deeper layers,” Miner and other researchers noted in 2021..

In the study, Miner labeled direct infection of humans by ancient pathogens released from permafrost as “currently improbable.”

However, Miner said he was concerned about what he called “Methuselah microbes” (named after the biblical figure with the longest lifespan). These are organisms that could bring the dynamics of ancient and extinct ecosystems to the present Arctic, with unknown consequences.

The reproduction of ancient microorganisms has the potential to alter soil composition and vegetative growth, potentially accelerating the effects of climate change, Miner said.

“We really don’t understand how these microbes would interact with the modern environment,” he said. “It’s not really an experience that I think any of us want to run.”

The best course of action, Miner said, is to try to stop the melt and the broader climate crisis and keep those dangers permanently buried in the permafrost.