Twenty-eight new viruses believed to be 15,000-years-old have been discovered surviving inside glaciers.
The viruses, which are unlike those known to science, were found in ice samples drilled from the Guliya ice cap in the Tibetan Plateau, in western China.
The scientists identified 33 viral genomes in total, and at least 28 of them are novel, they said. Four of the known viruses have been found to infect bacteria.
The novel viruses are not believed to be harmful to humans, according to the scientists who hope that the viruses can help them understand more about virus evolution and climate change.
In 2015, two ice cores were drilled out of the ice cap at extremely high altitudes of 22,000 feet above sea level.
The glaciers were formed over a long period of time and had collected dust, gases, and viruses the studys lead author Zhi-Ping Zhong, a researcher at the Ohio State Universitys Byrd Polar and Climate Research Center, said.
The glaciers in western China are not well-studied, and our goal is to use this information to reflect past environments, he added.
Co-author Matthew Sullivan, professor of microbiology at Ohio State, said that the method Mr Zhong used to decontaminate the cores to study the microbes and viruses could help them search for similar genetic sequences in other extreme icy environments, and places including Mars, the moon, or closer to home in Earths Atacama Desert.
The viruses found are not harmful to humans as they were made inactive by the chemistry of nucleic acids extraction, he added.
However, the studys conclusion states that melting glaciers could eventually release viruses that might infect humans.
It said: Glaciers potentially archive environmental conditions and microbes over tens to hundreds of thousands of years.
Unfortunately, glaciers around the world, including those from Tibetan Plateau and Himalaya, are rapidly shrinking, primarily due to the anthropogenic-enhanced warming of Earths ocean-atmosphere system.
Such melting will not only lead to the loss of those ancient, archived microbes and viruses but also release them to the environments in the future.
The scientists study was published last month in the journal Microbiome.
In August 2016, a 12-year-old boy died and at least 20 people were hospitalised after being infected with anthrax from the carcass of a dead reindeer in the Yamal Peninsula in the Arctic Circle, the BBC had reported.
It is believed that a heatwave that month thawed the permafrost that had frozen the infected reindeer for more than 75 years, allowing the bacterias spores to infect people.