Ancient viruses frozen in permafrost have the ability to infect single-cell modern organisms, a new study has shown.
The researchers revived viruses from up to 48,000 years ago and warn that there could be even more ancient viruses lurking in the ice, which could infect humans.
The researchers focused on giant viruses found frozen in ice – a type of pandoravirus which can affect amoebas.
The new research suggests that the viruses can infect modern organisms.
One-quarter of the northern hemisphere is underlain by permanently frozen ground, which is known as permafrost.
The researchers write, "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.
"Part of this organic matter also consists of revived cellular microbesas well as viruses that have remained dormant since prehistoric times."
The researchers collected giant virus specimens from sites in Siberia and used them to infect amoebas – building on previous research in 2014 and 2015, which demonstrated that two different viruses could infect amoebas.
The researchers focused on giant viruses which can affect amoebas, rather than other viruses which might be able to infect humans or other animals.
They dated the virus and found they had been dormant from between 27,000 and 48,500 years.
The researchers warn that as global warming intensifies, so do the risks of a virus that can infect humans emerging from permafrost.
"We believe our results with Acanthamoeba-infecting viruses can be extrapolated to many other DNA viruses capable of infecting humans or animals," they write.
"It is thus likely that ancient permafrost (eventually much older than 50,000 years, our limit solely dictated by the validity range of radiocarbon dating) will release these unknown viruses upon thawing.
‘How long these viruses could remain infectious once exposed to outdoor conditions (UV light, oxygen, heat), and how likely they will be to encounter and infect a suitable host in the interval, is yet impossible to estimate, but the risk is bound to increase in the context of global warming, in which permafrost thawing will keep accelerating, and more people will populate the Arctic in the wake of industrial ventures.’
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