Researchers have raised concerns that “zombie viruses” may break free from their frozen prisons as a possible consequence of climate change.
Despite having lain dormant for tens of thousands of years, ancient viruses found in permafrost can still infect amoeba once revived, according to a recently-published study by researchers from France, Germany and Russia.
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The reserchers collected several giant virus specimens from frozen ground in Siberia and tested to see if they could still infect modern single-celled organisms.
Although the “zombie” viruses in question are only capable of infecting amoeba, the findings have raised concerns that climate change could revive other ancient pathogens – ones to which humans may be susceptible.
The full findings of the study were published in the journal Viruses.
MSN reports: The study was undertaken by palaeovirologist Professor Jean-Michel Claverie of France’s Aix-Marseille University and his colleagues.
They said: “One quarter of the northern hemisphere is underlain by permanently frozen ground, referred to as permafrost.
“Due to climate warning, 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.
“Part of this organic matter also consists of revived cellular microbes […] as well as viruses that have remained dormant since prehistorical times.”
The researchers continued: “The literature abounds on descriptions of the rich and diverse prokaryotic microbiomes found in permafrost.”
However, they added, “no additional report about ‘live’ viruses have been published since the two original studies describing pithovirus (in 2014) and mollivirus (in 2015).
“This wrongly suggests that such occurrences are rare and that ‘zombie viruses’ are not a public health threat.
“To restore an appreciation closer to reality, we report the preliminary characterizations of 13 new viruses isolated from seven different ancient Siberian permafrost samples, one from the Lena river and one from Kamchatka cryosol.”
In their aforementioned previous works, the team showed both that a 30,000-year-old specimen of pithovirus could be revived and that it remained infectious; and that mollivirus, once defrosted, was capable of infecting an amoeba.
The new study follow-up the same protocol. For safety reasons, the researchers only collected so-called giant viruses – those 200-400 nanometres in diameter – which can only affect amoeba, rather than humans or any other creatures.