After obtaining seven ancient permafrost samples, scientists from the French National Centre for Scientific Research were able to document 13 never-before-seen viruses that had been lying dormant in the ice, Science Alert reports.
The same researchers found a 30,000-year-old virus in 2014 which was trapped in permafrost. Notably, it was still able to infect organisms. Now, they've beaten their own record with a find that's 48,500 years old, which they named Pandoravirus yedoma, according to Science Alert.
The scientists, who called these "zombie viruses" a public health threat, pointed to global warming as an ongoing risk that could result in the release of deadly pathogens from long ago.
"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 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."
As Global News notes,
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 belong to the following sub-types; pandoravirus, cedratvirus, megavirus, pacmanvirus and pithovirus - and are considered "giant" because they are large and easy to spot using light microscopy.