The news is chilling. What if, freed from its icy cocoon by global warming, the future Covid-19 came to us from the Far North? At first glance, it is the fear that can seize us on reading a Canadian study published this Wednesday in the Royal Society’s journal of biological research, Proceedings B, which is interested in a possible “viral overflow” coming from the Arctic. The most stoic will reply that we have been talking for years about the risks associated with the melting of the permafrost, which would release ancient gases and toxins. So what’s new about this study? Do we really need to protect ourselves against Greenlandic cholera? 20 minutes took out his microscope to study the case.
What does the Canadian study say?
The researchers took samples from the bed of a river feeding Lake Hazen, located beyond the Arctic Circle in the far north of Canada, as well as sediments from the bottom of the lake, 300 m deep and below two meters of ice cream. They then sequenced and studied the DNA and RNA of the viruses found, then compared their evolution to that of their hosts, algae and fungi.
This is where global warming comes into play. As the ice melts, more and more sediment is likely to be transported into the lake. At the same time, the surroundings of the lake, hitherto very inhospitable, could be colonized by lichens, mosses, and why not insects and then birds. And poof! That makes, not Chocapic, but contacts between the Ebola of the North and the arctic bee. Who could then spread the virus further south… “The probability of dramatic events remains very low”, however tempers Audrée Lemieux, author of the study, in the current circumstances.
What new does this study tell us?
Beware of confusion: this study does not look at the “ticking time bomb” of permafrost, but at the melting of glaciers. In other words, “we are not talking about reactivating viruses or old bacteria, but about viruses that live in modern glaciers”, details for 20 minutes Régis Debruyne, paleogeneticist at the National Museum of Natural History. No potentially deadly viruses once in circulation and suddenly trapped in the ice here, but many micro-organisms adapted to the glacial environment, and which “for the vast majority have plants and fungi as their host”.
Until now, studies were “a bit of a dead end” on the viruses in these soils, admits the paleogeneticist. The Canadian study thus makes it possible “to document the modern biodiversity” of a hostile environment which we “know little about”. “We realize that there are a lot of RNA viruses in this environment, which is not surprising. It corresponds well to the flora “which thrives there, he assesses.
Is there a risk of seeing a Covid come from the ice?
Paradoxically, the fact that these microscopic yetis are already very much alive and clinging to a local species of fungus or ant can make us optimistic. “The majority of hosts are very far from us, if viruses were to change hosts it would rather be from one fungus to another”, reassures Régis Debruyne. This is the whole point of the Canadian study, which compares the evolution of viruses to that of their hosts: “have they evolved with the host, where do they have already changed? ask the researchers. It is this second category of virus that we should be most wary of, a virus that has already passed from porcini mushrooms to boletes being more likely to cling to bats before flourishing in humans.
“For viruses too, it will be to adapt to global warming or disappear”, argues Régis Debruyne, faced with “an increasingly temperate fauna and flora”. The paleogenetician salutes in passing the “caution” of the study, and wishes to “stay measured on what it tells us”. According to him, “the risk of zoonosis is much greater with what we have seen in Asia than in the Far North”. In addition, be careful not to misunderstand the term “viral overflow”: nothing to do with the invasion of hordes of viruses, basing like birds of prey on our megalopolises and our immune systems without suitable defence; in fact, it characterizes a “change of equilibrium, with a host-dependent virus that could spread by changing hosts”. No more no less.