So-called ‘zombie’ viruses, which have spent up to 48,500 years frozen in the ground, could wake up when permafrost [permafrost] are melting due to climate change, scientists warn.
Noticeably warmer temperatures in the Arctic are already thawing these soils in the region. It is the permanently frozen layer below the Earth’s surface.
Researchers are trying to assess the level of danger bacteria and viruses trapped inside humans could pose – and carefully reviving some of them in the process.
“Fortunately, we can reasonably expect that an epidemic caused by a revived prehistoric pathogen can be quickly brought under control with the modern antibiotics at our disposal. […] However, bacteria with antibiotic-resistant genes appear to prevail in permafrost,” wrote the authors of a study published in February in the journal Viruses.
The same study warns that “the situation would be much more catastrophic in the case of plant, animal or human diseases caused by the revival of an ancient unknown virus” for which there would be no specific treatment or readily available vaccine.
Melting permafrost in Siberia has been linked to outbreaks of anthrax in reindeer, as extremely hot summers have caused a resurgence of ancient anthrax spores in animal burial sites.
In this latest study, French researcher Jean-Michel Claverie and his team reported that they were able to isolate and revive several ancient permafrost viruses, including a giant virus variant (Pithovirus) found in a 27,000-year-old permafrost sample that contained many mammoth.
Most of the viruses isolated were from the family Pandoraviridae, a family of double-stranded DNA viruses that infect amoebae – very small, simple organisms consisting of a single cell.
Unknown viruses have not yet been discovered
“This study confirms the ability of large DNA viruses infecting Acanthamoeba to remain infectious after more than 48,500 years spent in deep permafrost,” the authors wrote.
To be safe, 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 in the remains of mammoths, woolly rhinos or prehistoric horses preserved in the permafrost.
“Without the need to embark on such a risky project, we believe that our results with viruses that infect Acanthamoeba can be extended to many other DNA viruses capable of infecting humans or animals,” Claverie and her team wrote.
They also warned that as yet unknown viruses are likely to be released as the permafrost thaws.
“How long these viruses can remain infectious when exposed to external conditions (UV light, oxygen, heat) and how likely they are to find and infect a suitable host during this time is still impossible to estimate,” the researchers said.
“But the risk is likely to increase in the context of global warming, where permafrost thaw will continue to accelerate and more people will inhabit the Arctic as a result of industrial developments.”