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Climate change is unleashing ancient "zombie viruses" as ice layers melt

Climate change is revealing secrets trapped within our planet’s permafrost. As the icy layers melt at an alarming rate, they are uncovering organisms thought to be extinct – ancient “zombie viruses” that have been perfectly preserved for thousands of years. Scientists are discovering that these long-dormant microbes still possess the potential to infect and spread.

As global warming accelerates, the permafrost is thawing increasingly fast, along with the potential for zombie viruses to become infectious again. This warning comes from an international team of researchers from Russia, Germany, and France. The team includes experts in genomics, microbiology, and geoscience, some of whom have been tracking these re-emerging zombie viruses for almost a decade. The findings were published earlier this year in the journal Viruses.

Early warning signs

1918 Influenza virus

One of the earliest signs of the viral resurrection came from a somewhat unexpected place. In the late 1990s, Swedish pathologist Dr. Johan V. Hultin found RNA of the 1918 Influenza virus in the lungs of an Inuit woman buried nearly 80 years prior in a mass grave of influenza victims near a remote village outside Brevig Mission, Alaska. 

The discovery was possible because the permafrost had preserved enough RNA from the virus to enable researchers to sequence the entire 1918 strain’s genome. But this victory was a double-edged sword, heralding the potential for other diseases long frozen in the ice to re-emerge in our modern world.

Two giant viruses emerge in Siberia

Another zombie virus, Pithovirus sibericum, was discovered 100 feet beneath the Siberian permafrost in 2014. This ancient virus is so gigantic that it can be seen under an ordinary high school-style light microscope. 

French scientists from the University of Aix-Marseille managed to resurrect the 30,000-year-old P. sibericum by exposing amoebas to the virus. “This is the first time we’ve seen a virus that’s still infectious after this length of time,” said ProfessorJean-Michel Claverie.

While P. sibericum does not pose an immediate threat to humans or animals, its re-emergence serves as a stark warning. The scientists noted the ease with which these new viruses were isolated, suggesting that infectious particles of many other viruses specific to various hosts — including humans and animals — probably remain abundant in ancient permafrost.

Mollivirus sibericum, another giant virus, was found alongside P. sibericum in the same 30,000-year-old Siberian permafrost samples. Though not a direct threat to humans or animals, the proximity of these two giant viruses left scientists concerned about the potential treasure trove of pathogens that the permafrost might be hiding.

“We cannot rule out that distant viruses of ancient Siberian human (or animal) populations could reemerge as Arctic permafrost layers melt and/or are disrupted by industrial activities,” the researchers warned in their 2015 study.

The return of smallpox

Smallpox was eradicated by the World Health Organization in 1980. However, in 2004, French and Russian scientists discovered traces of smallpox in an icy 300-year-old Siberian mummy, frozen in the tundra of Russia’s Sakha Republic.

The chilling discovery can be traced back to the late 17th to early 18th centuries when the Siberian region was gripped by a severe smallpox outbreak. This mummy was discovered in a mass grave, a hastily arranged burial site from that era, preserved perfectly in the permafrost. Notably, this burial was unusual, as it contained not one but five frozen mummies, all believed to be victims of the same smallpox outbreak.

Climate change and an unclear future

For the authors of the new paper in the journal Viruses, this discovery of the 2004 smallpox virus serves as a grim example of the potential threat thawing permafrost may pose. “Probably for safety/regulatory reasons, there were not follow-up studies attempting to “revive” these viruses (fortunately).”

However, the lack of attempts to reanimate these viruses does not discount the possibility that they might revive on their own, given the right conditions. Permafrost is melting at unprecedented rates, potentially setting the stage for ancient pathogens to return. “Very few studies have been published on this subject,” said the researchers.

While these zombie viruses may not pose an immediate threat, their re-emergence is a stark reminder of the potential health risks associated with climate change. As scientists continue to study these ancient pathogens, they underscore the importance of understanding and addressing the profound impacts of global warming on our planet’s frozen frontiers.


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