“Z” Is For Zombie Virus

The thawing of the permafrost may expose a vast store of ancient viruses, according to a team of European researchers, who say they have found 13 previously unknown pathogens that had been trapped in the previously frozen ground of Russia’s vast Siberian region.

The scientists found one virus that they estimated had been stranded under a lake for more than 48,500 years and they said it highlights a potential new danger from a warming planet: what they called ‘zombie viruses’.

The same team of French, Russian and German researchers previously isolated ancient viruses from the permafrost and published their findings in 2015. This concentration of fresh viruses suggests that such pathogens are probably more common in the tundra than previously believed. “Every time we look, we will find a virus,” said Jean-Michel Claverie, a co-author of the study and an emeritus professor of virology at Aix-Marseille Université in France, in a phone interview. “It’s a done deal. We know that every time we’re going to look for viruses, infectious viruses in permafrost, we are going to find some.”

Although the ones they studied were infectious only to amoebas, the researchers said that there was a risk that other viruses trapped in the permafrost for millennia could spread to humans and other animals.

Virologists who were not involved in the research said the specter of future pandemics being unleashed from the Siberian steppe ranks low on the list of current public health threats. Most new — or ancient — viruses are not dangerous, and the ones that survive the deep freeze for thousands of years tend not to be in the category of coronaviruses and other highly infectious viruses that lead to pandemics.

The European team’s findings have not yet been peer-reviewed. But independent virologists said that their findings seemed plausible, and relied on the same techniques that have produced other vetted results.

The risks from viruses pent up in the Arctic are worth monitoring. Smallpox, for example, has a genetic structure that can hold up under long-term freezing, and if people stumble upon the defrosted corpses of smallpox victims, there is a chance they could be infected anew. Other categories of virus — such as the coronaviruses that cause covid-19 — are more fragile and less likely to survive the deep freeze.

“In nature we have a big natural freezer, which is the Siberian permafrost,” said Paulo Verardi, a virologist who is the head of the Department of Pathobiology and Veterinary Science at the University of Connecticut. “And that can be a little bit concerning,” especially if pathogens are frozen inside animals or people.” However he added If you do the risk assessment, this is very low.” 

For the most recent research, the European team took samples from several sites in Siberia over a series of years over the past eight years. The viruses they found — of an unusually large type that infects amoebas — were last active thousands, and in some cases, tens of thousands of years ago. 

Researchers say the chance of humans stumbling upon the carcasses of humans or animals is increasing, especially in Russia, whose far-north reaches are more densely settled than Arctic regions in other countries. The team gathered some of their samples in Yakutsk, a regional capital and one of Russia’s fastest-growing cities due to a mining boom.

The warming permafrost has been blamed for outbreaks of infectious disease before. A 2016 outbreak of anthrax hit a remote Siberian village and was linked to a 75-year-old reindeer carcass that had emerged from the frozen ground. 

Article published December 2, 2022 by Michael Birnbaum and Ellen, Washington Post