Giant virus awakes from Siberian slumber

After 30,000 years in the permafrost, viral infectious powers remain undiminished. James Mitchell Crow reports.

Despite spending 30,000 on ice, Pithovirus sibericum was none the worse for wear, electron microscopy confirmed. – Julia Bartoli and Chantal Abergel, IGS and CNRS-AMU

“Giant virus roused from 30,000-year-old Siberian permafrost.” It sounds like something from a sci-fi plot, but it’s true.

French scientists Chantal Abergel and Jean-Michel Claverie from Aix-Marseille University reported their finding in the Proceedings of the National Academy of Sciences this March.

The virus, thawed from a chunk of Siberian permafrost, turns out to be the largest ever found – some 10 times bigger than average. Abergel and Claverie first identified these giant viruses just a decade ago and have searched for them across the planet – even in a pond at Melbourne’s La Trobe University. Only a handful of giant virus species are known, but the revived specimen, named Pithovirus sibericum, suggests they might be more widespread than previously thought.

P. sibericum woke from its icy sleep none the worse for wear and infected the captive amoeba used as bait.

While this virus seems harmless to humans, who knows what else is lurking in the permafrost. “These are clearly infectious agents,” says Geoffrey Shellam, a virologist at the University of Western Australia. Only a few studies have ever previously looked for viruses entombed in permafrost, so it is “always possible” that human pathogens might emerge, he says.

Clearly there is more to worry about from melting permafrost than just the greenhouse gases that are predicted to bubble out.

The lair of the sleeping virus: the top few inches of permafrost thaw each summer.
Dave G. Houser/Corbis

But while the risk of thawing a deadly ancient virus is probably small, the warming climate is already giving more mundane pathogens the upper hand. In the tropics, higher altitudes and their cooler temperatures have provided people with a refuge from malaria-carrying mosquitos. But as temperatures rise, these mosquitos are also appearing in the highlands. In a study published in Science in March, Mercedes Pascual at the University of Michigan and her colleagues reported a clear correlation.

“We saw an upward expansion of malaria cases to higher altitudes in warmer years.” The team predicts hundreds of thousands more malaria infections in Africa and South America from just a one-degree rise in temperature as upland cities warm.

“Our findings underscore the size of the problem and emphasise the need for sustained intervention efforts in these regions,” Pascual said.

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