The ‘zombie viruses’ are alive after almost 50 thousand years: the study

The heat melts the permafrost and brings to light viruses ‘frozen’ for tens of thousands of years

Higher temperatures affect the permafrost, the layer of frozen soil. The partial melting of ‘permafrost’ can affect viruses that have been dormant for thousands of years. This is the picture outlined by CNN, quoting in particular the words of Kimberley Miner, a climate scientist who works at the Jet Propulsion Laboratory at NASA’s California Institute of Technology in Pasadena. “There are several things that are worrying in relation to permafrost, this really shows why it is extremely important to keep as much permafrost as frozen as possible,” she says. Permafrost covers one-fifth of the Northern Hemisphere.

Partial thawing of the layer carries risks, as highlighted by another scholar, Jean-Michel Claverie, professor emeritus of medicine and genomics at the University of Marseille. The scientist examined permafrost samples taken in Siberia to look for what he calls ‘zombie viruses’. The scientist studies particular types of viruses discovered in 2003, they are visible through a normal microscope due to their size. In 2014, the professor – we read on CNN – managed to ‘give life back’ to a virus isolated from the permafrost. The virus, through the use of cell cultures, has regained its infectious characteristics after 30,000 years. To be safe, the experiment involved a virus capable of affecting only single-celled organisms, not animals or humans. In 2015, the team repeated their study of a virus that can affect amoebae. In the latest research, published Feb. 18 in the journal Virus, Claverie isolated several strains of virus from multiple permafrost samples taken from seven different locations across Siberia and demonstrated that each strain could infect cultured amoeba cells. The oldest virus dates back to 48,500 years ago. The youngest has ‘only’ 27,000.

“We consider these viruses that infect the amoeba as surrogates for all other possible viruses that could be found in the permafrost,” Claverie explains to CNN. “We see traces of many, many, many other viruses. We know they’re there. We don’t know for sure if they’re still alive. But our reasoning is that if the amoeba viruses are still alive, there’s no reason why other viruses are not yet alive and capable of infecting their hosts”.

Traces of viruses and bacteria that can infect humans have already been identified in the permafrost. In the fragment of a lung taken from the body of a woman, exhumed in 1997 from the permafrost in a village on the Seward Peninsula in Alaska, genomic material of the flu strain responsible for the 1918 pandemic was identified. In 2012, scientists confirmed that the remains 300-year-old mummified of a woman buried in Siberia contained traces of the virus that causes smallpox.

Are there real risks associated with melting permafrost? Scientists don’t know how long any ‘frozen’ viruses could remain effective once exposed to today’s conditions. Nor can it be established with certainty how likely it is that the virus will encounter a suitable host. Not all viruses are pathogens that can cause disease: some are benign or even beneficial to their hosts. However, notes Claverie, “the risk is set to increase in the context of global warming where permafrost thawing will continue to accelerate and more people will populate the Arctic as a result of industrial initiatives.”