Ancient viruses lurking in polar ice caps

Prehistoric viruses are lying dormant in the polar ice caps-and a bout of warm weather could release them into the atmosphere, sparking new epidemics.

This news, published in New Scientist, follows the discovery, for the first time, of an ancient virus in Arctic ice. The virus, found deep within the Greenland icepack, is known as a tomato mosaic tobamovirus (ToMV), a common plant pathogen. The discovery suggests that other viruses, such as ancient strains of flu, polio and smallpox, may also be entombed and could make a comeback.

“We don’t know the survival rate, or how often they get back into the environment. But it certainly is possible,” says Tom Starmer of Syracuse University in New York.

Starmer’s colleagues Scott Rogers and John Castello of the State University of New York in Syracuse had earlier found ToMV in clouds and fog. The virus can survive in such environments because it belongs to a family with particularly tough protein coats. “Since it’s widespread, moves in the atmosphere and is very stable, we deduced that we would find it in the Arctic ice,” says Rogers.

The team says that a brief rise in temperature could unleash the entombed viruses. “The ice is melting constantly around the poles,” says Rogers. If released, they could cause outbreaks of disease. “If you’ve got these things lying in the ice for a thousand years or more and their usual host has not had to deal with them, this may be a source of epidemics,” says Alvin Smith, a virologist at Oregon State University in Corvallis. He has already found evidence that caliciviruses, which can cause diarrhoea, periodically re-emerge from the oceans, causing new infections.

The findings may answer some puzzling questions, Smith adds. Viruses evolve fast, continually changing their protein coats. Yet identical caliciviruses have appeared at 20-year intervals on opposite sides of the US, he says. “How did these viruses stay the same for so long? Where have they been hanging out?” He thinks they might have spent years trapped in polar ice before re-emerging to strike again.

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