Permafrost: "Viruses infectious to humans could be reactivated"

Text by: Romain Philips Follow

Over the years, more and more viruses, sometimes completely unknown to science, are discovered in frozen soils. With the melting of the ice and drilling activities in permafrost (permafrost, in English), unknown viruses sometimes dating back several tens of thousands of years, whose dangerousness for humans is not yet proven, could revisit the day.

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One is a director, the other is an assistant director and the two of them, Jean-Michel Claverie and Chantal Abergel, run the Genomic and Structural Information (IGS) laboratory in Marseille. This couple of virologists has specialized for several years in the search for viruses in permafrost. They notably discovered, in 2015, a giant virus, dating from around 30,000 years ago , in the frozen Siberian lands. Today, they believe that viruses that have been kept in permafrost for tens of thousands of years could be released and cause a health problem. Interview with virus hunters.

RFI: You are conducting research on viruses in permafrost, are we sure today that viruses dating back several tens of thousands of years imprisoned in this frozen soil can be reactivated ?

Chantal Abergel: We chose to use a model system that allows us to validate the fact that there may be viruses that are still reactivable in permafrost . Obviously, none of those that have been reactivated are infectious to humans. On the other hand, if there are infectious viruses for humans in the same environment, in the same way, they can be reactivated from these same soils.

Jean-Michel Claverie: The proof of concept has been made that yes, viruses dating back 40,000 years can still be infectious today. I was in Siberia last August to reproduce experiments in order to convince people that the discoveries that we made were not the possible result of external contamination. So we redid the experiments and very clearly, we are able to reactivate other types of virus. It is clear that up to 40,000 years, we do not know for beyond, a virus is capable of surviving. This suggests that viruses infectious to humans could be reactivated.

Is global warming a risk that could worsen the release of these viruses?

CA: The risks in terms of quantity are much lower in ice than in permafrost, but there is obviously a major change that is generated by these massive melts. Anyway, it impacts ecosystems and reactivating things that have been frozen for tens of thousands of years has an impact on the planet. There is no doubt about it.

JMC: The real problem is permafrost, because the ice is relatively sterile. It's frozen water and there really aren't any microbes in it. It is an environment that does not lend itself particularly well to the conservation over long periods of time of living organisms. While permafrost is richer in microbes of all kinds since it is soil that has accumulated (sediment, humus, plants ...). It dates back a very long time and has been able to be stored in frozen form for a period of up to a million years.

►Listen to: Climate change, a threat to permafrost

The melting surface layer is called the active layer. It is this part which releases viruses and microbes each year that were frozen a few years earlier. In the summer of 2016, there was an epidemic of anthrax ( anthrax ) which was due to the fact that, 70 years earlier, there must have been an epidemic in the reindeer herds. But summer had never been hot enough for us to descend so low into the permafrost layer. But in 2016, it was very hot so the ice melted further and reindeer were contaminated due to carcasses and soils that contained the remnants of the epidemic. It was not very serious before, because nobody lived there, but in 2016, there are still several breeders who were infected and a 12-year-old child who died.

With global warming and melting ice, certain areas, in particular Siberian permafrost, are becoming more and more exploitable for their resources and therefore attract more people, is this an additional risk?

One of the two Siberian craters, which appeared a short time ago, formed in the permafrost of an energy-rich region, nearly 2,000 kilometers from Moscow. AFP PHOTO / HO / PRESS SERVICE OF THE GOVERNOR OF THE YAMALO-NENETS

CA: This is the most critical point. In fact, the surface layer that will melt will go up to one meter, or even maximum two meters. But permafrost is really very massive depths and therefore obviously by going to find the resources which are found buried deeply, we will move tons and tons of frozen earth which will obviously have an impact on the modern system.

JMC : The real danger today is global warming which makes it possible to transport very heavy industrial equipment to these regions to go and drill and create surface mines. Because the preamble to all mining industrial activities is to remove the entire layer of permafrost that prevents access to oil or ore. Companies will therefore drill in the ground and the danger will be to bring microbes that have seen no one for a million years into contact with human beings. We risk coming into contact with things that are still infectious. All disaster scenarios are absolutely possible. There is no way at this time to assess their probability.

Could a virus released from permafrost cause an epidemic phenomenon ?

CA: If we highlight the two points: the areas more and more accessible with the melting of the ice and the fact that there will be more and more workers who will come to work to extract from these soils , which means that we will increase human concentration. There, reactivating a virus that could be pathogenic for humans will have a major impact on the population who will be there. We will certainly be on numbers of people significantly lower than what we can have in China at present with the coronavirus , but we will have the risk of generating a small epidemic. Where we will have to be alert is that we must above all not let these people return without taking health precautions to avoid precisely that there is a spread of a virus that could really infect humans.

JMC: On the drilling platforms, people are not in luxury hotels, they are relatively crowded on top of each other and have very close contacts. This is obviously very conducive to the rapid spread of a virus. In a drilling rig for example, if someone has the flu, in a week, everyone is infected.

The danger of these places is that we will put more and more people there who will live in a group and there is the possibility that, without close medical services, we will repatriate them if they are sick or when 'they're going home. With the coronavirus, the incubation time is 14 days, but if it is longer, people have time to travel a lot, to go on vacation, to come back and you have epidemic capacities at that time which have increased tenfold compared to a virus that is as visible as that of the coronavirus.

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