It’s a scenario straight out of The X-Files: A prehistoric pathogen, isolated for millennia in Arctic ice, comes to light in the modern world.

The catch is that it’s not science fiction--and thanks to the great Arctic thaw, the discovery suggests an emerging public health worry.

French scientists announced this week that working in the lab, they have found a “giant virus” in a 30,000-year-old sample of permafrost from Siberia.

It is the second giant virus isolated from the same permafrost sample in two years. The team found each one by infecting Acanthamoeba, a common contemporary protozoan, with viral material from the sample.

“That fact that two different viruses retain their infectivity in prehistorical permafrost layers should be of concern in a context of global warming,” the scientists wrote in a paper published in the Proceedings of the National Academy of Sciences.

“If we are not careful, and we industrialize these areas without putting safeguards in place, we run the risk of one day waking up viruses such as smallpox that we thought were eradicated,” researcher Jean-Michel Claverie told the news service AFP. “A few viral particles that are still infectious may be enough, in the presence of a vulnerable host, to revive potentially pathogenic viruses.”

The mining and fossil fuel industries are eager to expand into the Arctic as the region’s thawing ice cover opens access to mineral and fossil fuel deposits in remote areas, some of them in important habitat for whales, walruses, seals, fish, and other Arctic species.

Russia is already pumping oil above the Arctic Circle, while Norway’s state oil company has attempted to strike oil in the Barents Sea, and Dutch oil giant Shell is prospecting in the Chukchi Sea north of Alaska.

This newly discovered pathogen, named Mollivirus sibericum, is 0.6 microns long and has more than 500 genes. By contrast, the contemporary influenza A and B viruses each contain eight genes.

Viruses are classed as “giant” when they are longer than half a micron, or about 0.00002 inch.