‘Zombie’ viruses that have spent up to 48,500 years frozen in the ground could reawaken when permafrost thaws due to climate change, scientists warn.
Significantly warmer temperatures in the Arctic are already thawing the region’s permafrost, the permanently frozen layer beneath the earth’s surface.
Researchers are now trying to assess how much risk the bacteria and viruses trapped inside could pose to humans, and are reviving some in the process.
“Fortunately, we can reasonably hope that an epidemic caused by a reanimated prehistoric pathogenic bacterium can be quickly controlled by the modern antibiotics at our disposal […] even though bacteria carrying antibiotic resistance genes appear to be surprisingly prevalent in permafrost,” authors of a study published in February in Virus magazine he wrote.
He warned that “the situation would be much more dire in the case of plant, animal or human diseases caused by the resurgence of an ancient unknown virus” for which there would be no specific cure or vaccine immediately available.
Thawing permafrost in Siberia has already been linked to anthrax outbreaks in reindeer, as exceptionally hot summers have caused ancient anthrax spores to resurface from animal graveyards.
In this latest study, French researcher Jean-Michel Claverie and his team reported that they have succeeded in isolating and reviving several ancient viruses from permafrost, including a giant virus strain (Pithovirus) found in a permafrost sample of 27,000 years containing much mammoth wool.
Most of the virus isolates belonged to the Pandoraviridae family, a family of double-stranded DNA viruses that infect amoebae, very small and simple organisms consisting of only one cell.
Unknown viruses yet to be discovered
“This study confirms the ability of large DNA viruses that infect Acanthamoeba to remain infectious after more than 48,500 years spent in deep permafrost,” the authors wrote.
For safety reasons, Claverie and her team have focused on reviving prehistoric viruses that target single-celled amoebae rather than animals or humans.
Other scientists in Russia are currently looking for ‘paleoviruses’ directly from the remains of mammoths, woolly rhinos or prehistoric horses preserved in permafrost.
“Without the need to embark on such a risky project, we believe our results with viruses that infect Acanthamoeba can be extrapolated to many other DNA viruses capable of infecting humans or animals,” wrote Claverie and her team.
They warned that as yet unknown viruses are likely to be released as the permafrost melts.
“How long these viruses might remain infectious once exposed to external conditions (UV light, oxygen, heat) and how likely they are to encounter and infect a suitable host in between is still impossible to estimate,” they said.
“But the risk is set to increase in the context of global warming, where permafrost thawing will continue to accelerate and more people will populate the Arctic in the wake of industrial initiatives.”