Status: 03.01.2023 06:30 a.m
Researchers were able to reactivate viruses that had been frozen in the permafrost for thousands of years in the laboratory. As a result of climate change, such pathogens could increasingly thaw out and also infect people. But the biggest danger is different.
It’s not the yeti that lurks as a danger deep in the ice. An international research team succeeded in reactivating viruses that had been preserved by permafrost for thousands of years. They recently published the results of their research on so-called “zombie viruses” in a preprint study. The team led by Jean-Marie Alempic from the University of Marseille had already discovered two functional viruses in the permafrost in 2014 and 2015. The scientists have now published the status of their research on 13 other previously unknown viruses from the ice.
Permafrost soils are huge freezers
But how is it that viruses that have been dormant since prehistoric times become active again thousands of years later? Permafrost soils are like a natural freezer, explains Guido Grosse, head of the Permafrost Research Section at the Alfred Wegener Institute. He was involved in collecting the soil samples from Siberia that are now being analyzed in Marseille.
Many of the arctic ice sheets have existed since the last ice age. In some regions you can even find the remains of mammoths, explains Grosse: not only bones, but also preserved hair, flesh and blood. Unlike tropical or temperate climates, the organic matter in the frozen soil is not decomposed. Bacteria responsible for the decay process only become active when the permafrost thaws.
The eternal ice is thawing
Permafrost soils are mainly found in very cold regions such as Siberia or Alaska. There is also a place in Germany where alpine permafrost occurs: the Zugspitze. Perma or permafrost soils get their name from the fact that the temperature of the soil has been below zero degrees Celsius for at least two consecutive years.
In the future, however, there could be less and less permafrost. Even the eternal ice is melting due to climate change, and the permafrost soils are turning into swamps. As the permafrost melts, not only climate-damaging methane and carbon are released. Animal carcasses and plant remains that have been trapped in the permafrost for thousands of years also thaw. And with them the viruses that they carried when they froze.
If climate change continues at this rapid pace and global warming cannot be kept to a minimum, 75 percent of permafrost could disappear before the end of this century, says Grosse. The fact that the “zombie viruses” wake up naturally from their slumber could become a reality in the near future.
The thawing soil in Siberia is also releasing animal carcasses, like this head of an Ice Age wolf. Thanks to the extremely low temperatures, the brain, coat, tissues and even the tongue were perfectly preserved.
Image: AFP
Millennium-old viruses still functional
The researchers from Marseille were able to show that these viruses can become active again in the laboratory. In the study, you used Acanthamoeba castellanii – a genus of amoeba – as bait for the virus. The result: All 13 viruses were infectious and attacked the amoebas.
It is no surprise that viruses that have been frozen can multiply again. After all, it is the common method to store viruses for research at minus 80 degrees, says Albert Osterhaus, Director of the Research Center for Emerging Infections and Zoonoses at the University of Veterinary Medicine in Hanover.
How long the viruses remained infectious once exposed to natural conditions is unclear. The researchers from Marseille hope that their publication will attract other scientists to their research. The study situation is still sparse and the risks emanating from the thawing of the permafrost must be further researched, they write.
Bacterial pathogens are also released
Viruses are not the only pathogens that could pose a threat. Bacterial pathogens are also released. The preprint study states that pathogenic microorganisms up to 120,000 years old could also thaw. Some of them are related to current bacterial pathogens. Examples are the anthrax pathogen Bacillus anthracis, streptococci or staphylococci.
More recently, Bacillus anthracis spores could have caused large-scale reindeer die-offs, for example. The theory of the researchers from Marseille: The spores were released as a result of the permafrost thawing as a result of above-average hot summers and led to anthrax epidemics among the animals. In 2016, anthrax also broke out among humans in northern Siberia, presumably because of this Deutschlandfunk reported.
According to the researchers, however, bacterial pathogens could be stopped using today’s antibiotics. It is different with viruses. The corona pandemic has shown that very specific treatments and vaccines have to be developed for each new virus that would not be immediately available.
A health risk for humans?
In this case, the 13 identified viruses infected amoebas – under optimal laboratory conditions. However, it is quite conceivable that viruses that can infect humans will thaw out, explains permafrost researcher Grosse. The big question is what lies dormant in the permafrost and also in glaciers.
The veterinarian and virologist Osterhaus estimates the danger from viruses that are preserved in frozen animal carcasses thousands of years old to be rather low. According to him, the probability would be slightly higher for younger, human corpses from the glacier ice. Because these pathogens could already affect humans and not just specifically animals or amoebas.
Greater danger comes from today’s wild animals
In any case, the risk of people coming into contact with thawed pathogens has increased. Regions in the Arctic are increasingly being populated and used to extract raw materials, while the ice is increasingly thawing. However, it is unclear how great the danger posed by the pathogens is and how many different viruses and bacteria are slumbering in the ice.
“The chance that such viruses lead to really big problems is small, but never 100 percent absent,” explains Osterhaus. He considers contact with wild animals living today to be a much greater danger. This has just been experienced with the corona pandemic. Many experts assume that the coronavirus was transmitted from bats to humans.