A group of scientists led by Jean-Michel Claverie analyzed soil samples from Siberian permafrost in search of so-called zombie viruses, which have been dormant for thousands of years and could be brought back to life by global warming.
The film industry is fascinated by dystopias and post-apocalyptic scenarios, and many film or television productions are based on the possibility of microorganisms appearing out of nowhere to directly attack, decimate or destroy humanity. Invariably, these scenarios feature a terrifying landscape and a handful of survivors fighting mutants, zombies, or other survivors on a devastated planet.
The last of these productions is the series The last of us. Although it has the fungus as a protonist cordyceps unilateralis and not a virus, in its first scene a scientist asks the audience of a 1968 television program what would happen if the temperature of the planet “increased slightly”.
Permafrost, the frozen layer of the ground… but not
Word permafrost comes from English, from permanentpermanent and frost, frost. For something to be considered permafrost, it must remain frozen for two consecutive years. Furthermore, most of it is in the northern hemisphere and represents almost a quarter of the planet’s land area. It is mainly concentrated in the Arctic region, particularly in Siberia, Alaska, parts of Canada and Greenland, although it is also found in the Pyrenees, for example.
Permafrost has two layers, the surface active layer or molisol, which reaches a depth of one meter and usually thaws, and the permafrost, the deepest frozen layer, which can reach up to 1,500 meters in northeastern Siberia.
Doctor Jean-Michel Claverie explains in a article For ThinkGlobalHealth, despite the popular belief that permafrost is frozen, “regions north of the Arctic Circle are not icy expanses permanently covered with snow” and, in some spots, “although the average annual temperature does not exceed 10°C negative, remains above zero from June to September, occasionally reaching 30°C.”
Summer temperatures mean that each year a vegetation cover grows in the active layer, composed of a diverse fauna and a complex microbial system. In this cycle, this layer of living matter decomposes and freezes again. The ground is permanently frozen, but not covered in ice or snow.
Explosive cocktail: global warming, permafrost and carbon
Those permafrost features that remained stable for 400,000 years in the Arctic are now changing. During the 21st century there will be an average increase in the Earth’s temperature of 1.5°C compared to the pre-industrial era, but that’s it the Arctic is warming two to three times faster than temperate regions.
Summer melting of mollussols will reach ever greater depths, and permafrost cliffs in coastal or river areas will erode more rapidly. This will increase the release and reactivation of permafrost microbes, including late Pleistocene (last 100,000 years) ancient ones.
Furthermore, the amount of carbon trapped in permafrost is about twice that found in the atmosphere. As permafrost is lost, decomposed organic matter is released in the form of carbon dioxide and methane, the two main greenhouse gases, again contributing to global warming (which will again contribute to permafrost loss).
In turn, melting ice has made the north coast of Siberia more accessible by sea, so the area increasingly attracts mining companies, oil and natural gas industries. On the one hand, these industries can accelerate the destruction of permafrost, and on the other hand, the population of hitherto sparsely populated areas will slowly increase. This could increase the risk of spreading a potential virus that affects humans.
Microorganisms that come back to life
Two investigations of 2014 It is 2015 by Jean Marie Claverie, the latter in collaboration with his wife, Dr. Chantal Abergel, has already “resurrected” two viruses trapped in Siberian permafrost for 30,000 years. Indeed, his work gave rise to a new field of study in evolutionary biology, paleovirology.
The two viruses discovered by these studies, Pithovirus sibericum It is Mollivirus sibericumthese are called “giant viruses” because they are so large that they can be seen under a normal microscope.
A new to study published in February 2023 and led by Claverie revived seven new amoeba viruses, hitherto unknown to humanity, but which have now reached the outside world from the melting permafrost.
Claverie’s team analyzed soil samples taken from Siberian permafrost to see if there were infectious viral particles in viruses that were nearly 50,000 years old. The researchers used amoebas as bait, and the ancient viruses soon infected these lab-grown amoeba cells.
For safety, the viruses used in these investigations were carefully chosen from those that cannot attack humans or animals.
Do we have to worry about permafrost viruses?
The rebirth of viruses so ancient that they infect amoeba suggests that permafrost thaw, whether due to global warming or industrial exploitation of the circumpolar regions, could pose future threats to human or animal health.
The thinking behind these investigations may sound alarming, but in 2016 a anthrax outbreak it has killed thousands of reindeer, sickened humans and even killed a child in the Yamalo Nenets in the Siberian tundra. That year’s heat wave affected permafrost melting and released ancient spores from the Bacillus anthracis, probably from the frozen carcass of an infected reindeer. It had been 75 years since there had been an outbreak, specifically since the last reindeer immunization.
Claverie’s concern is that her research will not be taken into account beyond a curiosity, since permafrost is a huge reservoir, something like a snow globe that contains microorganisms that humanity has known and against which it can at least fight, and others that are much older and that, as their studies show, may be viable. The consequences of balloon rupture and release of its contents can be disastrous.
An update on eukaryotic viruses revived from ancient permafrost
in-depth study of Mollivirus sibericuma new 30,000-year-old giant virus that infects acanthamoeba
Reindeer Anthrax in the Russian Arctic, 2016: Climatic Determinants of Outbreak and Vaccination Efficacy
Thirty thousand year old distant relative of giant icosahedral DNA viruses with pandoravirus morphology