Canadian scientists found that an increase in glacier melt at Lake Hazen, the Arctic’s largest lake by volume and a location in George Clooney’s film The Midnight Sky, was linked to a greater risk of viral spillover, where a virus infects a new host for the first time. Melting glaciers were considered a proxy of climate change, which is causing their retreat globally.
The team from the University of Ottawa, led by Audrée Lemieux, gathered soil and sediment from the lake and sequenced the RNA and DNA in the samples. The researchers found signatures of viruses and their potential hosts including animals, plants and fungi. They then ran an algorithm recently developed by a different research team, which assesses the chance of coevolution or symbiosis among unrelated groups of organisms. The algorithm allowed the team to gauge the risk of spillover, and suggested this was higher in lake samples nearer to the point where larger tributaries – carrying more meltwater from nearby glaciers – flow into the lake.
“Our main finding is we show that for this specific lake, the spillover risk increases with the melting of glaciers. It’s not the same thing as predicting pandemics – we’re not crying wolf,” says Lemieux.
She says the risk of infectious diseases emerging from the Arctic is low today due to the region’s paucity of “bridge vectors”, such as mosquitoes, that can spread viruses to other species. However, the researchers note that climate change not only melts glaciers, but is also expected to cause more species to move towards the poles, which they warn “could have dramatic effect in the High Arctic”.
Exactly how glacier melt might increase spillover risk isn’t entirely clear from simply running the algorithm. Co-author Stéphane Aris-Brosou says one idea is that extra run-off simply increases the mixing of species because their local environment is disturbed, physically bringing together viruses and potential new hosts that wouldn’t otherwise encounter each other.
Most of the viruses found were plant and fungal ones. Other researchers question how many would be sufficiently intact, or in high enough concentrations, to remain infectious. “Much of the fragmented DNA or RNA they find will represent degraded viral genomes that no longer present a risk,” says Alex Greenwood at the Leibniz Institute for Zoo and Wildlife Research in Germany.
Lemieux and Aris-Brosou say another caveat is that this is the first time the spillover algorithm has been used in this way, so more studies will be needed to calibrate the true risk.
The threat of diseases emerging from the Arctic due to a warming world came to the fore in 2016 with a deadly anthrax outbreak in people in Siberia linked to the thawing of frozen ground uncovering a long-dead infected reindeer. “Are there potentially new viruses that the melting of the permafrost is going to wake up? As scientists, we ought to know, but we are really into the unknown unknowns,” says Aris-Brosou. Lemieux is now studying the team’s data to see if she can identify new viruses.
Reference: bioRxiv, DOI: 10.1101/2021.08.23.457348
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