The Arctic permafrost was once an area full of vegetation. But it’s been freezing for 35,000 years or so. Every summer it thaws slightly, and every winter it refreezes.
As climate change sets in, the summers have got longer and the winters are warmer. This means more of the permafrost melts, and the remnants of that vegetation—protected from decomposition by the freezing temperatures—is exposed.
As it melts, microbes and other forms of life will reawaken. What forgotten pathogens lie beneath?
And then, as they watched, a virus appeared in their viewfinder: Pithovirus sibericum, a massive ovular virion that had survived 30,000 years frozen in the ice core. It was also the largest virion ever discovered.
“We tried to isolate amoeba viruses without knowing they were going to be giant viruses—and a totally different type of virus than we already know appeared,” Claverie said. “It turns out the viruses we are getting [in the permafrost] are extremely abnormal, extremely fancy.”
Claverie and Abergel’s viruses aren’t a threat to humanity—yet. But human pathogens have also survived freezing and thawing in the permafrost. Last summer, an outbreak of anthrax in Siberia infected dozens of people and killed one child. The vector of disease is thought to be the thawing and decaying carcass of a reindeer killed in 1941.
And a team of Canadian scientists recently found a strain of bacteria, Paenibacillus, in a cave in New Mexico that had been closed off for more than 4 million years. Though harmless to humans, the ancient bacteria was resistant to most clinical antibiotics, including most of the newest and most aggressive. The discovery suggested that bacteria can survive the most exotic and remote environments.
The problem is compounded by our desire to access precious metals, rare earths, petrol, gas and gold throughout the arctic. If, say, Russia wants to access them, millions of tonnes of permafrost needs to be moved for the first time in millions of years.
Even more worrisome are the microbes we don’t know. “No one really understands why Neanderthals went extinct,” Claverie said. Sometimes, he catches himself when talking about these possible permafrost-locked diseases—they may have threatened humans or human relatives in the past, he’ll say. Then, he’ll change tense, emphasizing that they could do so again.