Melting glaciers expose viruses – this is how researchers assess the risk

One of the clearest signs of global warming is melting glaciers. With every inch that shrinks, they remind us that the Earth is getting warmer.

Their loss has consequences: Melting glaciers in the Himalayas lead to flooding in some areas and dry periods in others because the rivers are no longer fed by glacier water.

Researchers have now examined another danger in more detail. Namely the danger that viruses lie dormant in the glacial ice. The results of the study were published on October 19 in the scientific journal The Royal Society Publishing.

Viruses frozen in glaciers can spread to new hosts during thawing and continue to spread. The jumping of viruses to a new host is referred to in technical jargon as a viral spillover. Examples include the Corona and Ebola viruses, which were originally only found in wild animals before spreading to humans.

The risk of such a viral spillover, Dr. Stéphane Aris-Brosou of the University of Ottawa in Canada using the example of Lake Hazen. Located in the northernmost part of Canada, this freshwater lake is about the size of Lake Constance and is fed by the surrounding glaciers. It is, as it were, a reservoir of melted glacial ice – and therefore also of viruses.

To find out which viruses are in the glaciers, Aris-Brosou and his team genetically analyzed the bottom and lake sediments of Lake Hazen.

The DNA and RNA segments that were sequenced were then linked to potential hosts — in Hazener Lake’s case, these were animals, plants and fungi found in the area. Finally, the viral spillover risk was calculated using a computer algorithm.

As Aris-Brosou explains, viruses are more likely to infect hosts that are genetically similar. For this reason, his team has studied the evolutionary development of viruses and hosts to look for similarities and differences. The researchers concluded that spillovers on eukaryotes were greatest where most of the glacial water flowed into the lake. Eukaryotes are living things whose cells have a nucleus – ie humans, animals, plants, algae and fungi.

Their conclusion is supported by another study, which argues that eroding landscapes — such as a melting glacier in this case — facilitated the spread of pathogens. This is due to the so-called co-evolution of hosts and pathogens. In other words, a major change in a landscape can bring about a change in both viruses and hosts, which can facilitate the jump from viruses to new hosts.

Nevertheless, Aris-Brosou’s team makes it all clear: predicting a high risk of spillovers does not mean predicting actual spillovers or pandemics. For a truly dramatic scenario, multiple factors would need to be present at the same time.

However, this is where climate change comes into play. Rising temperatures in the Arctic could shift the natural habitats of several species further north. There they would encounter an environment with an increased risk of spillover, where as new hosts they could come into contact with old viruses and bacteria. The combination of these two factors — the melting glaciers at increased risk of overflow, as well as the shift in habitat — poses a risk, as Aris-Brosou writes:

However, the emphasis is on ‘ability’. Aris Brosou continues:

How this behaves in other environments needs further investigation.

What the researchers will also investigate further are the viruses found in the glacier water. They still have no information about the number of previously unknown viruses.

A study from Ohio State University last year found that unknown viruses can be found in glacial ice. The research team analyzed ice samples from a Tibetan plateau in China and found genetic material from 33 viruses. 28 of them were previously unknown. It is estimated that they are all about 15,000 years old.

But not only viruses in the ice are dangerous. For example, six years ago there was an outbreak of anthrax in northeastern Siberia. The bacterial infectious disease mainly affects cloven-hoofed ungulates and was actually considered eradicated – the latest outbreak was documented 75 years earlier.

It is believed that melting permafrost exposed the carcass of a reindeer, which was then eaten by nomads. A 12-year-old boy died as a result of the disease and 72 people were hospitalized. More than 2300 reindeer were killed. The danger has not been averted: the Siberian nomads bury both dead people and animals in the ice. As it thaws with rising temperatures, previously frozen pathogens end up in the groundwater.

What is certain at this point is that the Arctic is warming at a record pace. In addition to the numerous risks global warming poses to humans, melting, once eternal ice, poses other unknown dangers.