Zombie Viruses: Fascinating and a Little Frightening

March 10, 2023 – Of all the consequences of climate change, here’s one nobody counted on.

A team of European researchers digging into Siberian permafrost discovered and revived 13 types of prehistoric viruses. As the ancient frozen ground slowly loses its “perma” label due to rising temperatures, more and more microbes that have never encountered modern humans are resurfacing.

The researchers coined the isn’t-that-just-great term “zombie viruses” to describe previously dormant viruses that had been frozen in ice for tens of thousands of years – 27,000 to 48,500 years, in fact. 

The first question is obvious: This is fascinating, but is it a good idea? We’re still dealing with a certain mutating virus our immune systems have never encountered before.

The second question: What does it mean?

No Humans Were Harmed in This Study

The quick answer: The viruses observed here were only able to infect amoebae. But viruses that can infect humans do indeed exist in environments like permafrost.

The possibility that an unearthed, unknown virus will one day appear from seemingly nowhere and result in another pandemic is not necessarily zero. 

“There is an objective risk, and it is increasing,” says Jean-Michel Claverie, PhD, the lead researcher and an emeritus professor of genomics and bioinformatics at Aix-Marseille University in France. “However, we cannot put a number on this probability, specifically because we refuse to work with and revive human- and animal-infecting viruses. It would be much too dangerous.”

Based on Claverie and his team’s results, human- and animal-infecting viruses can indeed survive deep within the permafrost for extended periods of time. 

“From our research, we can deduce that other viruses present in the permafrost are likely still infectious,” says Claverie. “By sequencing the total DNA, we can detect the presence of viruses similar to those infecting animals or humans today.”

That said, the chances of something catastrophic happening from, say, humans exposed to thawed permafrost are slim. “[The microbes] would be quick to decay once they’re exposed to heat, UV light, and oxygen,” he says. 

Also, in places like Siberia where permafrost exists, people generally do not. So, some science fiction-inspired fears (we see you, fans of John Carpenter’s The Thing) are pretty unfounded. But if more people or companies begin to migrate toward the areas where these microbes are being released, the chances of a virus successfully infecting a host could be greater.

But What If …

So, what would happen – hypothetically – if the next deadly virus to overtake our planet came from the Arctic permafrost? Would we even be remotely prepared?

“There is a small risk that a frozen virus that gets unearthed is able to start an infection chain that ends up in humans,” says Adrian Liston, PhD, an immunologist and senior group leader at the Babraham Institute, a life sciences research institute at the University of Cambridge in the United Kingdom. Liston was not involved in the research discussed here. “On the one hand, we would not have preexisting immunity against it, so the initial ability to combat the infection is low. On the other hand, the virus would not be adapted to infect (modern-day) humans, so the chance of an initial infection being successful for the virus is extremely low.”

That’s something a lot of folks don’t understand: Today’s viruses and other infectious microbes are infectious only because they exist today. They have evolved to work within our modern immune systems – either for good or ill.

“‘Entry events’ do happen, very rarely, and they can shape human evolution,” says  Liston. “Major examples would be smallpox (a virus) and tuberculosis (a bacteria), which strongly influenced human evolution when they entered our species, selecting for the type of immune system that was able to fight them and killing off individuals with the ‘wrong’ type of immune system.”

And not all organisms are harmful. 

“There are many, many microbes that are beneficial to humans,” Liston says. “But generally speaking, these are microbes that have evolved for millions of years to work in harmony with our body, such as our microbiome, or have been selected for thousands of years to do beneficial chores for us, like yeast in making bread or brewing beer.” 

Some random frozen microbe is unlikely to impact us directly, but if it does, it is far more likely to be bad, Liston says.

For now, at least, we can rest easy knowing that Claverie and his team have no plans to revive dangerous viruses or retrieve more samples. “Because of the Russian-Ukrainian war, all of our collaborations have stopped. We are now focused on studying the viruses already in our lab and understand how they replicate and interact with their cellular hosts,” he says.

If anything, zombie viruses can at least remind us about the constant increasing effects that climate change will have on our lives and planet in the near future.

“The most important take-home message is that climate change is going to create unexpected problems,” says Liston. “It isn’t simply changes to weather, climate events, and sea levels rising. A whole cascade of secondary problems will be generated. New infections, some of which could go pandemic, are almost certainly going to happen because of climate change.”


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