A mysterious giant virus buried for 30,000 years in Siberian permafrost has been resurrected.
The virus only infects single-celled organisms and doesn't closely resemble any known pathogens that harm humans.
Even so, the new discovery raises the possibility that as the climate warms and exploration expands in long-untouched regions of Siberia, humans could release ancient or eradicated viruses. These could include Neanderthal viruses or even smallpox that have lain dormant in the ice for thousands of years.
"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," study co-author Jean-Michel Claverie, a bioinformatics researcher at Aix-Marseille University in France, wrote in an email. "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."
(A "non-zero" probability just means the chances of the event happening are not "impossible.")
In recent years, Claverie and his colleagues have discovered a host of giant viruses, which are as big as bacteria but lack characteristic cellular machinery and metabolism of those microorganisms. At least one family of these viruses likely evolved from single-celled parasites after losing essential genes, although the origins of other giant viruses remain a mystery, Claverie said. [Tiny Grandeur: Stunning Images of the Very Small]
In the researchers' hunt for more unknown pathogens, they took a second look at permafrost samples collected from Kolyma in the Russian Far East in 2000. Because the permafrost was layered along steep cliffs, drillers could extract samples from 30,000 years ago by drilling horizontally into the ice, thereby avoiding contamination from newer samples.
The team then took samples of this permafrost and put them in contact with amoebas (blob-like single-celled organisms) in Petri dishes. The researchers then waited to see what happened.
Some of the amoebas burst open and died. When the scientists investigated further, they found a virus had killed the amoebas.