Seven types of viruses that have lain frozen in the Siberian permafrost for thousands of years have been revived. The youngest were frozen for 27,000 years, while the oldest was on ice for 48,500 years 鈥� making it the most ancient virus resuscitated so far.
鈥�48,500 years is a world record,鈥� says聽 at Aix-Marseille University in France, who did the work with his colleagues. His team has previously revived two 30,000-year-old viruses from permafrost, the first of which was announced in 2014.
The team says the fact that all nine viruses remained capable of infecting cells shows that ancient viruses from melting permafrost are a threat to the health of plants and animals, including us.
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While 48,500 years may be a record for a virus, several groups claim to have revived bacteria trapped in sediments, ice or salt crystals that are up to 250 million years old. However, it remains unclear whether the organisms are actually that old or are much younger ones that contaminated samples.
The nine viruses Claverie鈥檚 team has revived are distinct from all previously known ones, he says, so are very unlikely to be from contamination of the sample by modern entities. The team discounted several other apparently revived viruses because their genomes were too similar to known ones.
It could well be possible to resurrect viruses that are much more than 48,500 years old, says Claverie. The deepest permafrost is up to a million years old. However, it is difficult to establish the age of ancient permafrost because standard radiocarbon dating doesn鈥檛 work beyond 50,000 years.
The 48,500-year-old virus came from permafrost 16 metres below the bottom of a lake in Yukechi Alas in Yakutia, Russia. It is a type of pandoravirus 鈥� a giant virus that infects single-cell organisms known as amoebas.
In fact, all the nine viruses revived by the team so far are giant amoeba-infecting viruses because this is all the team looks for. The researchers add permafrost samples to cultures of amoebas and inspect them under a microscope for signs of infection, which shows the virus is 鈥渁live鈥� and replicating.
If ancient giant viruses remain infectious after being frozen for such a long time, other kinds will too, says Claverie.
of the University of California, San Francisco, who has recreated plant viruses from long-frozen caribou faeces, agrees.
鈥淚f the authors are indeed isolating live viruses from ancient permafrost, it is likely that the even smaller, simpler mammalian viruses would also survive frozen for eons,鈥� says Delwart.
That means there is a risk of these ancient viruses infecting plants or animals, including people, if they defrost, says Claverie. This risk is being made greater by climate change melting permafrost, he says. 鈥淭here are bacteria and viruses coming out every day.鈥�
While there used to be few individuals in the Arctic to be exposed to such infection threats, says Claverie, more people are moving into the area to mine resources such as gold and diamonds. And the first step in mining is to strip away the upper layers of permafrost.
鈥淭here is a real danger,鈥� he says. 鈥淏ut it鈥檚 impossible to put a number on this risk.鈥�
Delwart thinks the risk of an ancient permafrost virus triggering a pandemic is much lower than that from the viruses circulating in domesticated and wild animals. 鈥淕lobal warming is terrifying enough without adding the release of frozen killer viruses to the long list of anticipated environmental disasters,鈥� he says.
But at Georgetown University in Washington DC says we need to take the danger seriously. 鈥淚t makes sense to understand all of the potential pathways for emergence so we can be as prepared as possible,鈥� she says. 鈥淭he threat of ancient viruses being released by the thawing permafrost is a very real threat.鈥�
Deliberate attempts to revive permafrost viruses could also be risky, says Claverie. His approach is safe because amoeba-infecting viruses can鈥檛 infect plants or animals, he says. However, a team at the State Research Center of Virology and Biotechnology VECTOR in Russia plans to revive , says Claverie.
鈥淭his is terrible,鈥� says Claverie. 鈥淚鈥檓 totally against it.鈥�
bioRxiv
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