Could global warming bring upon a new age of viral disease the world has never seen before…or seen 30,000 years ago? Some researchers think so. Recently, scientists uncovered the largest megavirus ever found. This virus, which is even larger than some bacteria, was found deep in a 30,000 year old ice core from permafrost in Siberia. Surprisingly, the virus was still able to infect amoebae after having spent 30 millennia frozen! This discovery has worried many scientists, because it suggests the possibility of the existence of ancient, human-targeting viruses and pathogens that could still be infectious. If climate change melts permafrost, it could result in the reintroduction of harmful, dormant viruses, risking human health, and unleashing a “Thawpocalypse”.
How It Was Discovered
The giant virus was discovered by French scientists Chantal Abergel and Jean-Michel Claverie of Aix-Marseille University in Siberian permafrost. Permafrost is found in extremely cold regions of the world and is a layer of permanently frozen soil. The scientists published their findings in Proceedings of the National Academy of Sciences just this month (March). After learning about a team of Russian scientists that revived an ancient plant from fruits buried in 30,000-year-old Siberian permafrost, Claverie “wondered if it was possible to revive a virus”. They exposed amoebae to the permafrost samples, and as amoebae began to dying, Abergel and Claverie’s team discovered the viruses, Pithovirus sibericum, inside.
Why It Surprised Scientists
Currently, Pithovirus sibericum is the only species in the genus Pithovirus. Its unique characteristics clearly set it apart from all previously known viruses. Pithovirus replicates itself in the host cell’s cytoplasm, as opposed to invading the nucleus, like most viruses. While an average virus measures around 20 to 300 nanometers, Pithovirus measures an astounding 1.5 micrometers. Although the average virus is about one one-hundredth the size of the average bacterium, Pithovirus is larger than some bacteria. Also, its capsid is 50% larger than the previous largest known viruses, pandoraviruses. As we learned in class, a capsid is the protein coat that surrounds a viral genome. However (to scientists’ surprise) pandoraviruses still have a larger genome that codes for many more proteins than the Pithovirus. Furthermore, only about one-third of its proteins resemble those of other viruses. “That huge particle is basically empty,” said Claverie, referring to the large capsid in comparison to the small genome, “We thought it was a property of viruses that they pack DNA extremely tightly into the smallest particle possible, but this guy is 150 times less compacted than any bacteriophage. We don’t understand anything anymore!”
Why Scientists Are Concerned
France’s National Centre for Scientific Research (CNRS) released a press statement saying “[The discovery] has important implications for public-health risks in connection with exploiting…resources in Arctic Circle regions that are becoming…more accessible through global warming. The revival of viruses that are considered to have been eradicated…is no longer limited to science fiction. The risk that this scenario could happen in real life has to be viewed realistically.” Abergel and Claverie are also concerned that global warming as well as mining and drilling in the Arctic could thaw more ancient viruses, posing as a threat to human health. Although large viruses usually target amoebae, there have been known cases of human infection by giant viruses. Some are even concerned that global warming could thaw frozen viruses and release them to the sea, where they could disperse widely. The viruses could come in contact with millions of people, with our scientists and doctors helpless due to lack of information on the foreign virus. Although this whole “Thawpolcalypse” scenario may be improbable, it is possible, so let’s all hope that ancient viruses stay frozen for a long time!