After lying dormant for at least 30,000 years, a giant virus has "come back to life," BBC News reported.

The dormant Pithovirus was buried in a deep layer of the Siberian permafrost and found by French scientists, but after it thawed it became infectious once again, BBC News reported. The virus only infects single-celled organisms and doesn't closely resemble any known pathogens that harm humans or animals, researchers said.

"This is the first time we've seen a virus that's still infectious after this length of time," Professor Jean-Michel Claverie from the National Center of Scientific Research at the University of Aix-Marseille told BBC News.

The new discovery raises the possibility that climate change and exploration of long-untouched regions of Siberia could release ancient or eradicated viruses, Fox News reported.  Neanderthal viruses or even smallpox that have lain dormant in the ice for thousands of years could also be resurrected.

"There is now a non-zero probability that the pathogenic microbes that bothered [ancient human populations] could be revived, and most likely infect us as well," Claverie, told Fox News. "Those pathogens could be banal bacteria (curable with antibiotics) or resistant bacteria or nasty viruses. If they have been extinct for a long time, then our immune system is no longer prepared to respond to them."

Researchers said their findings have important implications in terms of public health risks related to the exploitation of mining and energy resources in circumpolar regions, which may arise as a result of global warming. They said the probability o of the re-emergence of viruses needs to be estimated realistically.