The Arctic is currently warming at unprecedented rates because of global climate change, resulting in thawing of large tracts of permafrost soil. A great challenge is understanding the implications of permafrost thaw on human health and the environment. Permafrost is a reservoir of mostly uncharacterized microorganisms and viruses, many of which could be viable. Given our limited knowledge of permafrost-resident microbes, we also lack the basis to judge whether they pose risks to humans, animals, and plants. Here we delve into features of permafrost as a microbial habitat and discuss what is known about the potential for microbial pathogens to emerge in a warming climate as permafrost thaws. This review has broader implications for human health and ecosystem sustainability in the new Arctic environment that will emerge from a thawed permafrost landscape
