Scientists have revived a giant virus that was buried in Siberian ice for 30,000 years — and it is still infectious, Scientific American reports.

Fortunately, the virus only targets amoebae, but the researchers suggest that as earth's ice melts, other ancient viruses, with potential risks for human health, could return.

Named Pithovirus sibericum, the newly-thawed virus is the biggest ever found. At 1.5 micrometers long, it is comparable in size to a small bacterium.

Its name was inspired by the Greek word pithos, the large container used by the ancient Greeks to store wine and food. “We’re French, so we had to put wine in the story,” says evolutionary biologist Jean-Michel Claverie, who led the work with his wife Chantal Abergel.

The results of their work were published in Proceedings of the National Academy of Sciences.

Reviving ancient life forms

Two years ago, Claverie and Abergel's team learned that scientists in Russia had resurrected an ancient plant from fruits buried in 30,000-year-old Siberian permafrost. “If it was possible to revive a plant, I wondered if it was possible to revive a virus,” says Claverie.

Using permafrost samples provided by the Russian team, they fished for giant viruses by using amoebae — the typical targets of these pathogens — as bait. The amoebae started dying, and the team found giant-virus particles inside them.

Although giant viruses almost always target amoebae, Christelle Desnues, a virologist at the French National Center for Scientific Research in Marseilles, last year discovered signs that another giant virus, Marseillevirus, had infected an 11-month-old boy.

The boy had been hospitalized with inflamed lymph nodes, and Desnues' team discovered traces of Marseillevirus DNA in his blood, and the virus itself in a node. “It is clear that giant viruses cannot be seen as stand-alone freaks of nature,” she says. “They constitute an integral part of the virosphere with implications in diversity, evolution and even human health.”

Claverie and Abergel are concerned that rising global temperatures, along with mining and drilling operations in the Arctic, could thaw out many more ancient viruses that are still infectious and that could conceivably pose a threat to human health.

But Curtis Suttle, a virologist at the University of British Columbia in Vancouver, Canada, who was not involved in the work, notes that people already inhale thousands of viruses every day, and swallow billions whenever they swim in the sea.

The idea that melting ice would release harmful viruses, and that those viruses would circulate extensively enough to affect human health “stretches scientific rationality to the breaking point,” he says. “I would be much more concerned about the hundreds of millions of people who will be displaced by rising sea levels.”