Zombie virus revived?
Zombie apocalypse is a genre of fiction in which society collapses due to overwhelming swarms of zombies. Typically only a few individuals or small bands of survivors are left living. In some versions, the reason the dead rise and attack humans is unknown, in others, a parasite or infection is the cause, framing events much like a plague. Some stories have every corpse rise, regardless of the cause of death, whereas others require exposure to the infection.
The genre originated in the 1968 American horror film Night of the Living Dead, which was directed by George A. Romero, who took inspiration from the 1954 novel I Am Legend by Richard Matheson. Romero’s film introduced the concept of the flesh-eating zombie and spawned numerous other fictional works, including films, video games and literature.
The zombie apocalypse has been used as a metaphor for various contemporary fears, such as global contagion, the breakdown of society, and the end of the world. It has repeatedly been referenced in the media and inspired various fan activities such as zombie walks, making it a dominant genre in popular culture.
Warmer temperatures in the Arctic are thawing the region’s permafrost — a frozen layer of soil beneath the ground — and potentially stirring viruses that, after lying dormant for tens of thousands of years, could endanger animal and human health.
While a pandemic unleashed by a disease from the distant past sounds like the plot of a sci-fi movie, scientists warn that the risks, though low, are underappreciated. Chemical and radioactive waste that dates back to the Cold War, which has the potential to harm wildlife and disrupt ecosystems, may also be released during thaws.
“There’s a lot going on with the permafrost that is of concern, and (it) really shows why it’s super important that we keep as much of the permafrost frozen as possible,” said Kimberley Miner, a climate scientist at the NASA Jet Propulsion Laboratory at the California Institute of Technology in Pasadena, California.
What is “Permafrost”?
Contrary to the beliefs of most inhabitants of temperate zones (including many journalists), the regions located north of the Arctic Circle are not icy expanses permanently covered with snow. For instance, in Duvanny Yar, a popular permafrost research site—located on the mouth of the Kolyma River north of the 68th parallel in the Republic of Sakha, Yakutia—although the annual average temperature does not exceed -10°C there, it remains above zero from June to September, occasionally reaching 30°C. Each summer therefore sees the regrowth of a significant vegetation cover, made up of diverse fauna (arthropods, worms) and the proliferation of a complex microbial ecosystem (protozoa, bacteria, viruses).
At the return of each winter, this transient surface layer of living matter slowly decomposes and refreezes. Its accumulation and compaction over hundreds of years end up forming a sort of peat at a depth where the temperature never again reaches above 0°C, even in summer. This permanently frozen soil, called “permafrost,” is thus very different from ice (i.e. frozen water), with which it is frequently confused in popular media. The thickness of permafrost is delimited by two zones. At the surface (to a depth of about one meter), by what is called the “active layer,” the temperature of which rise above 0°C each summer. And at the bottom (which can reach up to 1,500 meters in northeastern Siberia, because of the geothermal gradient (Earth’s internal heat). Between top and bottom the permafrost temperatures remain relatively constant (between -15°C and -5°C).
Scientists for years have been warning about the dangers posed by viruses buried under ice caps in the Arctic and other places. Dubbed ‘zombie viruses’, they have the potential to unleash deadly strain of the disease that the present population is not equipped to handle. The threat has increased since rising temperatures due to global warming started melting the frozen ice. To better understand the risks associated with these ‘Zombie viruses’, a French scientist revived some of them from samples taken from Siberian permafrost, as per a report in Euro News. These viruses have spent thousands of years frozen in the ground.
It Is to be noted that a fifth of the Northern Hemisphere is covered in permafrost, which has long supported the Arctic tundra and boreal forests of Alaska, Canada and Russia. Together with ancient viruses, it acts as a kind of time capsule, preserving the mummified remains of several extinct creatures.
By reviving these bacteria and viruses, researchers are attempting to determine how much of a threat they may be to mankind. A study about the discovery has been published in the journal Viruses in which the researchers stated, “Fortunately, we can reasonably hope that an epidemic caused by a revived prehistoric pathogenic bacterium could be quickly controlled by the modern antibiotics at our disposal even though bacteria carrying antibiotic-resistance genes appear to be surprisingly prevalent in permafrost.”
The reason permafrost is a good storage medium isn’t just because it’s cold; it’s an oxygen-free environment that light doesn’t penetrate. But current day Arctic temperatures are warming up to four times faster than the rest of the planet, weakening the top layer of permafrost in the region.
To better understand the risks posed by frozen viruses, Jean-Michel Claverie, an Emeritus professor of medicine and genomics at the Aix-Marseille University School of Medicine in Marseille, France, has tested earth samples taken from Siberian permafrost to see whether any viral particles contained therein are still infectious. He’s in search of what he describes as “zombie viruses” — and he has found some.
The virus hunter:
Claverie studies a particular type of virus he first discovered in 2003. Known as giant viruses, they are much bigger than the typical variety and visible under a regular light microscope, rather than a more powerful electron microscope — which makes them a good model for this type of lab work.
His efforts to detect viruses frozen in permafrost were partly inspired by a team of Russian scientists who in 2012 revived a wildflower from a 30,000-year-old seed tissue found in a squirrel’s burrow. (Since then, scientists have also successfully brought ancient microscopic animals back to life.)
In 2014, he managed to revive a virus he and his team isolated from the permafrost, making it infectious for the first time in 30,000 years by inserting it into cultured cells. For safety, he’d chosen to study a virus that could only target single-celled amoebas, not animals or humans.
He repeated the feat in 2015, isolating a different virus type that also targeted amoebas. And in his latest research, published February 18 in the journal Viruses, Claverie and his team isolated several strains of ancient virus from multiple samples of permafrost taken from seven different places across Siberia and showed they could each infect cultured amoeba cells.
Those latest strains represent five new families of viruses, on top of the two he had revived previously. The oldest was almost 48,500 years old, based on radiocarbon dating of the soil, and came from a sample of earth taken from an underground lake 16 meters (52 feet) below the surface. The youngest samples, found in the stomach contents and coat of a woolly mammoth’s remains, were 27,000 years old.
That amoeba-infecting viruses are still infectious after so long is indicative of a potentially bigger problem, Claverie said. He fears people regard his research as a scientific curiosity and don’t perceive the prospect of ancient viruses coming back to life as a serious public health threat.
“We view these amoeba-infecting viruses as surrogates for all other possible viruses that might be in the permafrost,” Claverie told CNN.
“We see the traces of many, many, many other viruses,” he added. “So we know they are there. We don’t know for sure that they are still alive. But our reasoning is that if the amoeba viruses are still alive, there is no reason why the other viruses will not be still alive, and capable of infecting their own hosts."
Why it matters:
Calvary’s team only attempts to resurrect viruses that can’t infect people, plants, or animals, but they think those types of viruses could be revived from their frozen states, too.
“We view these amoeba-infecting viruses as surrogates for all other possible viruses that might be in the permafrost,” Calvary told CNN. “We see the traces of many, many, many other viruses, so we know they are there.”
“We don’t know for sure that they are still alive,” he continued, “but our reasoning is that if the amoeba viruses are still alive, there is no reason why the other viruses will not be still alive and capable of infecting their own hosts.”
Don’t panic: We already know that thawing permafrost can release microbes that harm human health — in 2016, a heat wave in Siberia exposed frozen reindeer that had been infected with the anthrax bacteria, which led to dozens of people being hospitalized and one boy dying.
However, while it is possible that a zombie virus could be a major threat to our health, it isn’t terribly likely — new viruses emerge regularly from living animals, and a permafrost virus would need to be highly contagious and capable of causing disease that we can’t readily treat.
Are zombie viruses dangerous?
The short answer is no.
Barr said it is “surprising” that scientists were able to recover viruses from almost 50,000 years ago but it is well known that viruses can be stored frozen for long periods of time.
“I ran a lab at Monas University and we freeze virus samples all the time and we can bring them out of the freezer and they’ll still be functional,” he said.
Barr said the key takeaway from this research is the viruses infected amoeba in the soil samples, not humans.
“Viruses have emerged from 50,000 years ago but these are viruses infect amoeba. It’s likely those amoeba lived in those soil samples 50,000 years ago and those viruses were frozen there.”
“If there was a frozen virus that could infect us, you would need to have frozen humans or human bodies from 50,000 years ago that died from a virus to revive a virus that could infect us.”
He said viruses are everywhere and many people are “terrified of the word virus after the pandemic” but the vast majority of viruses are actually good and don’t cause disease.
“This is nothing to be worried about.”
However, Brigitte Even Gard, professor emerita at Umea University’s Department of Clinical Microbiology in Sweden, said there should be better surveillance of the risk posed by potential pathogens in thawing permafrost, but also warned against an alarmist approach.
“You must remember our immune defence has been developed in close contact with microbiological surroundings.”
“If there is a virus hidden in the permafrost that we have not been in contact with for thousands of years, it might be that our immune defense is not sufficient.
“It is correct to have respect for the situation and be proactive and not just reactive. And the way to fight fear is to have knowledge.”