As the Northern climes warm, our species may soon be
vulnerable to ancient—even beyond ancient— bacteria and viruses. We are
familiar with pathogens to which our species has some immunity, built up from
repeated prior contact. As a species, we could lose everything from illnesses
in which the modern human body has no experience and thus no built-up defenses.
The full essay is at "Bacteria and Viruses in Melting Permafrost."