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 chilling warning follows the discovery, for the first time, of an ancient virus in Arctic ice. The virus, found deep within the Greenland ice pack, 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 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 (New Scientist, by Matt Walker, September 4, 1999).