Researchers at the University of Marseille have managed to reactivate thousands of years old viruses that were frozen under permafrost in the laboratory. Due to global warming, permafrost soils are starting to thaw, which means more pathogens are released and can spread to humans.
A quarter of the northern hemisphere is permanently covered by frozen ground. These permafrost soils can mostly be found in cold regions like Siberia or Alaska. But it is precisely this thick layer of ice that is now starting to melt more and more.
Under the permafrost is organic material, most of it broken down by carbon dioxide and methane. The release of these substances increases the greenhouse effect, which contributes significantly to the Earth’s temperature. Animal and plant carcasses also appear, and with them pathogens that can infect humans.
prehistoric viruses
Jean-Marie Alempic and her team discovered two functional viruses in permafrost in 2014 and 2015. In the course of their research, the researchers were able to reactivate viruses that had been dormant since prehistoric times. The status of their research on 13 other previously unknown ice viruses has now been published in a preprint study.
In their study, the researchers used a species of amoeba (Acanthamoeba castellanii) as a bait for the virus. All 13 viruses were contagious and attacked amoebas. It remains unclear how long “zombie viruses” remain infectious when they come into contact with nature. So far, the identified viruses have only been tested under ideal laboratory conditions.
bacteria released
With their research, Alempic and his team hope to entice other scientists to find out more about the effects of permafrost thinning. Guido Grosse, head of the permafrost research section at the Alfred Wegener Institute, explains to the “tagesschau” that it is quite possible for viruses that can infect humans to thaw. You don’t know what’s under the permafrost and glaciers.
However, not only viruses are released, but also bacterial pathogens. The preprint study states that pathogenic microorganisms up to 120,000 years old may be thawing. These are related to current bacterial pathogens such as the anthrax pathogen Bacillus anthracis, streptococci or staphylococci.
What danger is there for humans?
Albert Osterhaus, director of the Research Center for Emerging Infections and Zoonoses at the Hanover University of Veterinary Medicine, estimates that the risk of contracting viruses from frozen animal carcasses that are thousands of years old is low. Much more risky are younger human glacial ice corpses, as these pathogens can already infect people. Wild animals living today also pose a health risk, as has been known since the corona pandemic.
The likelihood of coming into contact with pathogens has increased, but it is still unclear what danger pathogens pose and how many different viruses and bacteria are lying dormant in the ice. “The chance of such viruses leading to really big problems is small, but never 100% absent”, explains Osterhaus.
Permafrost as a giant refrigerator
The fact that viruses have survived for so long is due to the Arctic ice sheet. This formed in the last ice age, over 10,000 years ago. Permafrost soils are like giant freezers, explains permafrost researcher Grosse. Remains such as bones, hair, meat and blood of mammoths have already been found in some regions of the world. Bacteria, which would otherwise start the decomposition process, only react when the permafrost thaws, meaning that the organic material in the frozen ground does not decompose.
A permafrost soil is classified as such if the soil temperature has been below zero degrees Celsius for at least two consecutive years. Grosse warns that, as a result of ongoing global warming, 75% of permafrost could disappear within this century.