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 atmosphere.
Soaring temperatures have the ability to discharge the viruses en-masse into a world that has no immunity against them.
The potency of these viruses is unknown, with some potentially lethal and others likely harmless.
Scientists from the US and China drilled down 165ft (50 meters) into the Tibetan plateau glacier to investigate any pathogens entombed within.
A five-year project allowed them to ensure they were detecting ancient viruses and not just picking up contamination from the modern world.
Removing the ice's top layer (0.5cm) with a bandsaw and washing it with ethanol and water ensured it was free from contamination.
They tested their procedure on artificial ice cores before applying it to the two ice cores in the study.
The team of academics then applied genetic and microbiology techniques to record all the DNA in the two ice cores they obtained.
'This is an exciting new area of research for us,' co-author Lonnie Thompson told Vice.
Writing in their paper, published online in the pre-print journal bioRxiv, the researchers write: 'Glacier ice harbors diverse microbes, yet the associated viruses and their impacts on ice microbiomes have been unexplored.'
Although the researchers refused to comment on their research as it has yet to be peer-reviewed they write that there is a great deal of interest in studying extinct viruses stored in glaciers.
However, this may be impossible as soaring temperatures around the world trigger glacial melting, destroying all records of the ancient microbial life trapped within.
Driven by climate change, the rate of ice thawing out in frozen regions is a concern for the scientists.
They write: 'At a minimum, this could lead to the loss of microbial and viral archives that could be diagnostic and informative of past Earth climate regimes; however, in a worst-case scenario, this ice melt could release pathogens into the environment.'
Scott Rogers, a professor at Bowling Green State University penned a book on the potential of dormant microbes in glaciers being released.
He believes that it could trigger an incurable plague that has the potential to sweep across the world, infecting humans with no immunity to the disease.
Professor Rogers writes in his book, titled Defrosting Ancient Microbes: Emerging Genomes in a Warmer World: 'The dangers encased in ice are real, and with the increases in melting of the ice worldwide, the risks from the release of pathogenic microbes also are increasing.'
A long-dormant microbe has already been released from ice as in 2016 an anthrax outbreak in Serbia was traced back to ancient permathrost thawing.
More than 2,300 reindeer died in the outbreak, in the Yamalo-Nenets region of Siberia with families evacuated from the region and troops brought in to contain the disease's spread.
Eight people were confirmed as infected with anthrax, which can be fatal, and dozens more underwent tests to ensure they were not infected.
© Associated Newspapers Ltd.