French scientists say they have revived a giant but harmless virus that had been locked in the Siberian permafrost for more than 30,000 years.
Wakening the long-dormant virus serves as a warning that unknown pathogens entombed in frozen soil may be roused by global warming, they said.
The virus, Pithovirus sibericum, was found in a 30-metre-deep sample of permanently frozen soil taken from coastal tundra in Chukotka, near the East Siberia Sea, where the average annual temperature is -13.4 degrees Celsius.
The team thawed the virus and watched it replicate in a culture in a petri dish, where it infected a simple single-cell organism called an amoeba.
Radiocarbon dating of the soil sample found that vegetation grew there more than 30,000 years ago, a time when mammoths and Neanderthals walked the Earth, according to a paper published in the US journal Proceedings of the National Academy of Sciences (PNAS).
P. sibericum is, on the scale of viruses, a giant. It has 500 genes, whereas the influenza virus has only eight.
It is the first in a new category of viral whoppers, a family known as Megaviridae, alongside two other categories that already exist.
The virus gets its name from “pithos,” the ancient Greek word for a jar, as it comes in an amphora shape.
At 1.5 millionths of a metre, it is so big it can be seen through an optical microscope, rather than a more powerful electron microscope.
Unlike the flu virus, though, P. sibericum is harmless to humans and animals, and only infects a type of amoeba called Acanthamoeba, the researchers said (Virus as therapy? Some Acanthamoeba can cause pretty nasty neurological disease in snakes (and humans) FB).
The work shows that viruses can survive being locked up in the permafrost for extremely long periods, France’s National Centre for Scientific Research (CNRS) said in a press statement.
“It has important implications for public-health risks in connection with exploiting mineral or energy resources in Arctic Circle regions that are becoming more and more accessible through global warming,” it said.
“The revival of viruses that are considered to have been eradicated, such as the smallpox virus, whose replication process is similar to that of Pithovirus, is no longer limited to science fiction.
“The risk that this scenario could happen in real life has to be viewed realistically.”