As Halloween approaches and seasonal temperatures reach record highs, global warming could bring back “zombie” bacteria and viruses that are thousands of years old.
“It is known in microbiology that viruses and bacteria that have been frozen for a very long time can be reactivated without losing their properties when the temperature rises above freezing,” confirms Benoit Barbeau, professor of biological sciences at UQAM and expert in virology.
If he had to bet on the probability that a “zombie” microorganism would rise from the ice and contaminate the human population, he would choose bacteria rather than viruses, whose properties are very different.
In his opinion, the chances of a virus finding a host and passing to humans are very low. “But nothing is impossible in science,” he says.
38,000 years old
A 38,000-year-old “zombie” virus was discovered 16m deep in Siberian permafrost by a French team last year. Previously unknown, it belonged to a group of 13 new viruses from the family Pandoraviridae that were able to infect host cells after laboratory manipulations, according to the article published in February 2023 in the journal Viruses. However, there is no reason for humans to worry. These viruses only infect amoebas.
Despite everything, according to the authors, preserving permafrost required special attention to be paid to these frozen microorganisms in order to prevent the release of new pathogens.
Viruses and bacteria, two worlds
In 2016, a 12-year-old boy died in Siberia after becoming infected by bacteria released from the carcass of a caribou that had been frozen for several decades. However, this famous death due to anthrax, which infected 90 people and caused the death of 2,000 caribou in Russia, remains an exception.
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You should know that viruses need a host to develop, while bacteria only need a suitable environment and a viable temperature. “A virus that thaws must immediately find an organism that can absorb it. It can be a cell or a complex organism such as a plant, fungus or insect. Without this host it will simply disappear,” explains Professor Barbeau.
The bacteria only need a culture medium and sufficient temperature to divide into 2, 4, 8, etc. Within a few days, the bacterial colony can begin to cause damage.
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Studying Extreme Viruses
Catherine Girard, a microbiologist specializing in the ecology of microorganisms in the Far North, has been traveling to one of the northernmost points on Earth, just 700 km from the North Pole, since 2009 to study viruses in extreme situations. “The aim of my research is to better understand the very fragile ecosystem of the cryosphere,” explains this professor from the University of Quebec in Chicoutimi to the journal.
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Fifteen percent of the continent in the Northern Hemisphere is permanently frozen ground. Contrary to what one might think, these environments are teeming with life, but science only knows a tiny fraction of it. “For example, I am interested in the microbial life that is at the bottom of the food chain during the very short period of time in which the glacier melts.”
The site of his research in Nunavut is too north for polar bears and sometimes mid-July snowstorms blow away tents, and the only complex living organisms are greenish mats of microscopic algae and nematodes. But it is the best place to study the “rock ‘n’ roll lifestyle of extreme microorganisms,” as the researcher puts it, capable of surviving polar cold and subsequent bombardment with UV rays.
She is surrounded by “zombie” viruses, but is afraid of nothing because she estimates the risk of infection to be “near zero”. Rather, it is this environment that has to fear human activity that threatens the fragile Arctic ecosystem.