Unknown ancient viruses up to 15,000 years old have been discovered lurking in prehistoric ice atop the Tibetan plateau. Scientists extracted two lumps of ice from a glacier and found a total of 33 pathogens frozen inside, with 28 of them never seen before by humans. Researchers say global warming is threatening to melt the world's glaciers and that under a 'worst-case scenario' the viruses could be released into the ...