Ancient viruses trapped in permafrost for thousands of years are waking up

As global temperatures continue to rise, the Arctic landscape is collapsing. Glaciers and ice caps are melting at an unprecedented rate and ground that has been frozen for millennia is beginning to melt.

The effects of rising sea levels and habitat loss are already being felt around the world, but another threat is beginning to lurk beneath the surface.

Permafrost is land that has remained completely frozen for at least two consecutive years. The oldest permafrost in the world, found in Siberia, has been frozen for over 650,000 years.

It is believed that around 1.7 trillion tonnes of carbon is sequestered in this frozen ground, which is released into the atmosphere when the permafrost thaws. But these greenhouse gases are not the only problem: microbes trapped in the soil for millennia are also beginning to emerge.

A single gram of permafrost can contain hundreds of thousands of species of dormant microbes, many of which are thought to be able to survive in extreme conditions (in 2016, an anthrax outbreak in northern Siberia killed a boy 12 years and thousands of animals). Unusually warm weather had accelerated permafrost thaw in the area, and the outbreak is thought to have been caused by anthrax spores released from a recently exposed reindeer carcass.

Pathogens once thought extinct, like smallpox, can also lurk under the frozen ground, as can ancient viruses to which we have no natural immunity and no effective vaccine or treatment.

In 2014, a group of French and Russian researchers reactivated a giant virus, containing hundreds of genes, which had been found under Siberian permafrost. The virus, known as pandoravirus, had lain dormant for 30,000 years under the ice. Although this particular virus only infects amoebas, its very existence proves that microbes locked in permafrost can still be activated thousands of years after they were first frozen.

“If amoebic viruses can survive under these conditions, there is no reason why other viruses should not survive as well,” said Jean-Michel Claverie, who led the research. Newsweek.

With fewer than 5 million people living near Arctic permafrost today, global warming is poised to open up new shipping lanes and reservoirs of resources, which in turn will increase trade and tourism in the region. As a result, people will be more likely to come into contact with these ancient pathogens.

“The public health risk comes from the accelerated release of previously frozen viruses combined with increased human exposure, as global warming also makes Arctic areas much more accessible to industrial development,” Claverie said.

Warming temperatures will also cause more animals to migrate north, bringing the viruses into contact with many new potential hosts. This increases the risk of viruses spreading from one species to another. Similar spillover events have been behind the emergence of recent pandemics such as SARS-CoV-2 and HIV.

In a recent study, published in the journal Proceedings of the Royal Society Bresearchers from the University of Ottawa in Canada used genetic analysis to assess how the risk of viral spread might increase due to rising global temperatures.

The research was conducted using soil and lake sediment samples collected from Canada’s Lake Hazen, the largest freshwater lake north of the Arctic Circle.

“We used glacier runoff as an indicator of climate change because it has been shown that a warming climate will increase glacier runoff on this specific lake,” said Stéphane Aris-Brosou, one of the co-authors. of the study. Newsweek. “In our paper, we found that overflow risk increased with runoff from glaciers – or climate change – in lake sediment samples.”

Melting glaciers release large amounts of meltwater and sediment into the lake each year, increasing turbulence and sediment deposition. This appears to have caused significant disruption to lake ecosystems and could increase the risk of viral spread.

“Due to increased meltwater as a result of warming temperatures, the turbidity of the lake has increased over the past 10 to 15 years, which is disturbing the bottom of the lake,” Aris-Brosou said. “This fragmentation of the aquatic habitat creates favorable conditions for overflows.

“Fragmentation creates barriers to gene flow, which increases differentiation between niches, thereby accelerating the coevolution of viruses and their hosts. This acceleration potentially leads to viral diversification.”

Aris-Brosou insisted that the results of the study were not produced to predict the next pandemic. On the contrary, the study indicated that as our planet continues to warm, the Arctic could become fertile ground for the emergence of future pandemics.

“This is more proof that we are changing our planet in a negative way, and we need to reconsider the way we live,” Aris-Brosou said.

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References:

Legendre M, et al., Thirty thousand years distant relative of giant icosahedral DNA virus with pandoravirus morphology, PNAS, 30 January 2014, https://doi.org/10.1073/pnas.1320670111

Lemieux A, et al., Viral spillover risk increases with climate change in High Arctic lake sediments, Proc. R. Soc. B., October 26, 2022, http://doi.org/10.1098/rspb.2022.1073

Liskova EA, Egorova IY, Selyaninov YO, et al., Reindeer Anthrax in the Russian Arctic, 2016: Climatic Determinants of the Epidemic and Effectiveness of Vaccination. Front. Veterinary. Sci., 2021 Jun 24, doi: 10.3389/fvets.2021.668420