Huge areas in the northern hemisphere are still dominated by permafrost: permanently frozen ground that is only superficially thawing. Enclosed in them, the remains of animals or plants survive for thousands of years almost unchanged – and with them the bacteria and viruses they once carried. A team led by Jean-Marie Alempic of the CNRS in Marseille managed to detect and reactivate 13 previously unknown virus types from matched samples, as the working group writes in an as yet unpublished study on bioRxiv.
The researchers estimate that one of the viruses could have survived 50,000 years in ice before becoming virulent again in laboratory cell cultures – a new world record. The same team previously resurrected a 30,000-year-old virus from permafrost. The current record holder is a giant amoeba-infecting virus now called Pandoravirus yedoma. It is so large that it can be detected with a standard light microscope, and it comes from a soil sample taken from an Arctic lake.
The other viruses also infected amoebae in cell cultures and thus became virulent again after thawing. The team isolated them from mammoth wool and the entrails of a frozen wolf, among other things. Alempic and company estimate that there may still be thousands of unknown viruses in permafrost, some of which could potentially infect humans. In view of the increasing use of permafrost areas and climate change, which is causing the ground to thaw, certain risks are emerging here, the researchers write.