French scientists have revived a ‘zombie virus’ in the lab that had been frozen in permafrost for 48,500 years. Although the researchers are not afraid that this could lead to another pandemic, it cannot be completely ruled out. The increasing thawing of the eternal ice due to climate change poses an uncertain health risk to humanity.
The warmer temperatures in the Arctic are thawing permafrost — a frozen layer beneath the earth — and could revive viruses that have been dormant for tens of thousands of years and could threaten human and animal health.
To better understand the dangers of frozen viruses, Jean-Michel Claverie, emeritus professor of medicine and genomics at the medical school of the University of Aix-Marseille in Marseille, has now examined soil samples from the Siberian permafrost to determine whether the virus particles contained therein are still contagious.
Inspiration from Russian researchers
The scientist is looking for so-called “zombie viruses” – and he has already found some. Claverie studies a specific type of pithovirus virus that he first discovered in 2003. These viruses, known as giant viruses, are much larger than the typical variety and are more visible under a standard light microscope than under a more powerful electron microscope – making them a good model for this kind of laboratory work.
His efforts to track viruses frozen in permafrost were inspired in part by a team of Russian scientists who, in 2012, revived a wildflower from 30,000-year-old seed tissue found in a squirrel’s burrow.
Virus contagious again
As Claverie now describes in a new research paper in the journal Viruses, in 2014 he and his team succeeded in reviving a virus isolated from the permafrost by introducing it into cultured cells. For safety reasons, he decided to study a virus that can only affect single-celled amoebas, but not animals or humans.
In 2015, it finally succeeded with another type of virus that also affects amoebas. The scientists were able to identify different strains of the ancient virus from different permafrost samples from different locations in Siberia — and infect amoebas with them. All 13 viruses were contagious and attacked the amoebas.
Oldest example almost 50,000 years old
These latest strains, now revived, represent five more new virus families in addition to the two. The oldest sample was nearly 48,500 years old and came from a soil sample taken from an underground lake 16 meters below the surface (carbon dating). The most recent samples found in the stomach contents and fur of the remains of a woolly mammoth were 27,000 years old.
Public health problem?
The fact that amoebaviruses are still contagious after such a long time points to a potentially bigger problem, Claverie said. He worries that people will see his research as a scientific curiosity and not see the prospect of ancient viruses coming back to life as a serious threat to public health.
“We consider these amoeba-infecting viruses as surrogates for all other possible viruses that could be in the permafrost,” Claverie told CNN.
However, it is still unclear how long the viruses remained contagious after being exposed to natural conditions. “But we assume that if the amoebaviruses are still alive, there’s no reason why the other viruses shouldn’t still be alive and able to infect their own hosts,” Claverie continued.
Viruses are not the only problem
However, viruses are not the only pathogens that can pose a health risk. Bacterial pathogens are also released. Pathogenic microorganisms that are up to 120,000 years old are also thawed in the samples – some of these are related to current bacterial pathogens, such as the anthrax pathogen Bacillus anthracis, streptococci or staphylococci.
According to the theory of the scientists from Marseille, this could have already led to a large reindeer death in 2016. As a result of the then warmer-than-average summer, Bacillus anthracis spores were released from the permafrost and an anthrax epidemic began among the animals.
Especially contact with wild animals as a threat
Contact with wildlife also poses the greatest risk for the transmission of viruses and bacteria to humans – a development that is partly caused by climate change and increasing land use. While in the latter case a simple administration of antibiotics is sufficient for treatment, a much more complex vaccine is required to potentially bypass viruses.
Source: Krone
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