Permafrost is this layer of frozen earth that makes up 25% of the land surface of the northern hemisphere. Formed during the last ice age, it has, by freezing, imprisoned a large number of elements: organic matter, gas, bacteria, viruses... The story could end there. But now, over the past thirty years, global warming has multiplied by 7 the rate of permafrost thawing. Here it wakes up and, in doing so, releases greenhouse gases that accelerate its own thawing, but also bacteria and viruses. It could even harbor countless infectious foci. What are the scientists' predictions? Is it already too late?