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As if from the plot of a movie, scientists recently discovered an ancient virus buried underneath the Siberian permafrost. This virus, Mollivirus sibericum, belongs to a group of other ancient viruses collectively known as "giant" viruses. Mollivirus sibericum is not unique in its discovery. In fact, since 2003 researches have found four other frozen giant viruses. Some worry that reawakening this so called "Frankenvirus" will lead to trouble but, rest assured, Mollivirus sibericum poses no real threat to humans. Of more concern is the role climate change plays in the discovery of ancient viruses.
Mollivirus sibericum is the second 30,000-year-old virus to be unearthed in the Siberian permafrost. The first, Pithovirus sibericum, was discovered in 2014 by the same set of French researchers from the French Centre National de la Recherche Scientifique. The researchers published a paper on their discovery of Mollivirus sibericum, which means "soft virus from Siberia," in the Proceedings of the National Academy of Sciences. Mollivirus sibericum is classified as "giant" because it can be viewed under a light microscope whereas most viruses can only be seen using an electron microscope. Giant viruses also contain significantly more genes than average viruses. Mollivirus sibericum for instance has more than 500 genes while the HIV virus has a measly 9 genes (Pandoraviruses, another type of giant virus can have up to 2,500 genes). 
Despite being frozen for 30,000 years, "a few viral particles that are still infectious may be enough, in the presence of a vulnerable host, to revive potentially pathogenic viruses," explains lead researcher Jean-Michel Claverie. The French team of scientists hope to revive Mollivirus sibericum from its dormancy by putting it in contact with a host organism, in this case a single-cell amoeba. Reawakening the virus poses no real threats to human health since Mollivirus sibericum only infects amoebas. To be on the safe side, researchers will first test to make sure that the virus is unable to reproduce in human and mice cells, which "they don't, of course," assures lead scientist Chantal Abergel.
Unfortunately, global warming is causing the Siberian permafrost to melt (the Arctic and subArctic regions are warming twice as fast as the rest of the world). As a result, more ancient viruses, which appear to be common in permafrost, may be liberated from their frozen state. In regards to climate change, the French team of scientists explain that "[the] fact that two different viruses retain their infectivity in prehistorical permafrost layers should be of concern in a context of global warming." Increased drilling and mining in the mineral rich Siberian region may also bring humans in contact with released ancient viruses. Theoretically speaking, the frozen viruses have the potential to cause infections once reawoken. However, the threat posed by the reawakening of these ancient viruses is of minimal concern to most virologists. Even if the viruses were revived, there is a very slim chance that they would be able to infect humans and then spread amongst us. Of more immediate worry is the impact global warming has on the geographic ranges of insects. As the world warms, insects that carry pathogenic viruses, such as mosquitoes, are able to move into previously uninhabitable regions. For example, the re-emergence of chikungunya virus in recent years is related to global warming.
Thankfully, you won't have to worry about catching a 30,000-year-old Siberian virus anytime soon. We'll leave that scenario to the movies.
Sources:
"Frankenvirus emerges from Siberia's frozen wasteland." Agence France Presse. September 8, 2015.
(Published online before print)
Vence, T. "Another Ancient Giant Virus Discovered."The Scientist. September 14, 2015.
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