Permafrost, a frozen layer of soil beneath the ground, is thawing as temperatures rise in the Arctic, potentially reawakening viruses that have lain dormant for thousands of years and posing a threat to animal and human health.
Despite the low likelihood of a pandemic being triggered by a disease from the past, scientists warn that the threat is being greatly underestimated. It is also possible that chemical and radioactive waste from the Cold War, which could be harmful to wildlife and disrupt ecosystems, would be released during thaws.
“There’s a lot going on with the permafrost that’s of concern, and (it) really shows why it’s super important that we keep as much of the permafrost frozen as possible,” said Kimberley Miner, a climate scientist at NASA’s Jet Propulsion Laboratory at the California Institute of Technology in Pasadena.
The Arctic tundra and boreal forests of Alaska, Canada, and Russia have been supported by permafrost for millennia, and it currently covers a fifth of the Northern Hemisphere. It’s like opening a time capsule, as it contains not only ancient viruses but also the mummified remains of several extinct animals that scientists have recently unearthed and studied. These include two cave lion cubs and a woolly rhino.
Permafrost is advantageous as a storage medium not only because it is cold, but also because it is an oxygen-free environment that is not exposed to light. The top layer of permafrost is melting as a result of the Arctic warming up to four times faster than the rest of the planet.
Scientists at the Aix-Marseille University School of Medicine in Marseille, France, led by Emeritus Professor of Medicine and Genomics Jean-Michel Claverie, have tested soil samples from Siberian permafrost to determine whether or not any viral particles contained therein are still infectious. There are “zombie viruses,” which he seeks and discovers.
To use a cliche, permafrost is a time capsule.
The Arctic’s tundra and boreal forests have survived for centuries thanks to permafrost, which covers 20% of the Northern Hemisphere. It’s like opening a time capsule, because inside you’ll find not only ancient viruses but also the perfectly preserved skeletons of long-lost animals like woolly rhinos and cave lion cubs.
Due to its inaccessibility to oxygen and sunlight, permafrost makes for an excellent storage medium. To the contrary, Nature reports that Arctic temperatures are increasing up to four times faster than global averages, thus weakening the outermost layer.
Retroviruses with a 48,500-year revival history
Reviving a virus from permafrost that had been dormant for 30,000 years required introducing it into cultured cells, which Jean-Michel Claverie and his team were able to accomplish in 2014. To play it safe, he researched a virus that only infected single-celled amoebas.
In 2015, he performed the same test again, this time with a different strain of virus. Claverie and his team isolated multiple ancient virus strains from seven sites in Siberian permafrost, and their findings were published on February 18 in Viruses.
Amoeba cells in culture were infected by each strain. Five new virus families were represented by the most recent strains, in addition to the two he had previously resurrected.
Between the oldest virus and the youngest virus, there was a difference of nearly 48,500 years. The youngest virus was found by Claverie and his team in a woolly mammoth’s bones.
Dangerous to the community’s health
That amoeba-infecting viruses can survive deep freeze testing suggests a serious issue, says Jean-Michel Claverie.
Because of this, Claverie worries that his findings will be dismissed as a scientific curiosity rather than the serious public health risk that the revival of long-extinct viruses represents.
He theorises that any other viruses that might be in the permafrost are just like the ones that infect amoebas.