Researchers from the French National Centre for Scientific Research have revived more than a dozen prehistoric viruses that were previously trapped deep within the Siberian permafrost, according to a pre-print study.
From seven ancient permafrost samples, scientists were able to document 13 never-before-seen viruses that have been lying dormant, frozen in ice, over tens of thousands of years.
In 2014, the same researchers unearthed a 30,000-year-old virus trapped in permafrost, the BBC reported. The discovery was groundbreaking because after all that time, the virus was still able to infect organisms. But now, they’ve beaten their own record by reviving a virus that is 48,500 years old.
The ancient virus was given the name Pandoravirus yedoma, which acknowledges its size and the type of permafrost soil that it was found in, according to Science Alert.
Scientists are thawing out these ancient viruses in order to assess their impacts on public health. As the permafrost, or permanently frozen ground, melts in the Northern Hemisphere, the thawing ice releases tons of trapped chemicals and microbes.
“Due to climate warming, irreversibly thawing permafrost is releasing organic matter frozen for up to a million years, most of which decomposes into carbon dioxide and methane, further enhancing the greenhouse effect,” the study’s authors wrote. “Part of this organic matter also consists of revived cellular microbes (prokaryotes, unicellular eukaryotes) as well as viruses that remained dormant since prehistorical times.”
Some of these “zombie viruses” could potentially be dangerous to humans, the authors warn. And, in fact, thawing permafrost has already claimed human lives.
In 2016, one child died and dozens of people were hospitalized after an anthrax outbreak in Siberia. Officials believe the outbreak started because a heat wave thawed the permafrost and unearthed a reindeer carcass infected with anthrax decades ago. About 2,300 reindeer died in the outbreak.
The revived viruses that researchers spotted belong to the following sub-types of viruses: pandoravirus, cedratvirus, megavirus, pacmanvirus and pithovirus. These viruses are considered “giant” because they’re large and easy to spot using light microscopy.
For this reason, researchers believe there are many other smaller viruses that have escaped scrutiny.
The scientists also used amoeba cells as “virus bait” to see which viruses were still active and capable of infecting an organism. The researchers said this limited their results to detecting only “lytic viruses,” which destroy their host, as opposed to other kinds of viruses that can merge with a host’s DNA.
One silver lining is that the study’s authors say there is a “negligible” risk of these amoeba-infecting viruses having a hazardous impact on humans. But that’s not to say that all ancient viruses are harmless.
The authors noted that the “risky” search for viruses found in the “permafrost-preserved remains of mammoths, woolly rhinoceros, or prehistoric horses” is another story altogether.
It’s unclear if these ancient viruses would be able to infect a host once exposed to outdoor conditions like heat, oxygen and UV rays. But researchers say the chance of such a situation is increasing as more of the permafrost thaws and more people begin to occupy the melting Arctic for commercial and industrial ventures.