15,000-year-old viruses never before seen by humans discovered in glacial ice

Columbus, Ohio – Glaciers can preserve all kinds of relics from the distant past. So could they also harbor a prehistoric pandemic? It’s possible. A team from Ohio State University has discovered a collection of never-before-seen viruses in the ice of a glacier in China.

Scientists say viral samples date back almost 15,000 years and could reveal how pathogens evolve over the centuries. Of the 33 viruses found trapped in the ice of the Tibetan Plateau, the team considers 28 to be completely new. About half of them also appear to have survived specifically because of the freezing conditions.

“These glaciers formed gradually, and along with the dust and gas, many viruses were also deposited in this ice,” says lead author Zhi-Ping Zhong, a researcher at the Byrd Polar and Climate Research Center in Ohio. , in a university press release. . “Glaciers in western China are not well studied and our goal is to use this information to reflect past environments. And viruses are one of those environments.

A viral timeline of Earth’s past

Scientists collected core samples from the Guliya ice sheet in 2015. This ice sits 22,000 feet above sea level and the researchers say layers have continued to build up there year after year. for thousands of years.

The study’s authors say this created a sort of timeline of everything in the atmosphere at different times in history; trap germs and show how the climate has changed since 13,000 BC.

“These are viruses that would have thrived in extreme environments,” adds Matthew Sullivan, study co-author and Ohio State professor of microbiology. “These viruses have gene signatures that help them infect cells in cold environments – just surreal genetic signatures for how a virus is able to survive in extreme conditions. These aren’t easy signatures to extract, and the method Zhi-Ping developed to decontaminate carrots and study microbes and viruses in ice could help us search for these genetic sequences in other extreme icy environments – Mars, for example, the moon, or closer to home in the Atacama Desert on Earth.

Where do these old viruses come from?

Viruses don’t share a common genetic background, so researchers say determining the origin of a new virus takes several steps. For the 33 viruses discovered in China, the team compared the known virus gene sets to the new strains.

The study found that four viruses in the Guliya ice cap belong to a family of viruses that typically infect bacteria. They also found that the viral concentrations of these germs were much lower than the amounts found by scientists in the oceans or the soil.

The team also claims that all of these new viruses probably came from soil or plants, not animals or early humans.

“We know very little about viruses and microbes in these extreme environments, and what really is there,” says senior author Lonnie Thompson, distinguished university professor of earth sciences at Ohio State . “Documenting and understanding this is extremely important: How do bacteria and viruses respond to climate change? What happens when we go from an ice age to a warm period like the one we are experiencing now? “

The study appears in the journal Microbiome.