8 ancient 'zombie viruses' that scientists have pulled from the melting permafrost

Permafrost is melting at rapid rates in the Russian Far East and could unleash unknown, long-dormant viruses.  (Image credit: Michael Robinson Chavez/The Washington Post via Getty Images)

Locked away in frigid Arctic soils and riverbeds is a world teeming with ancient microbes. Bacteria and viruses that existed thousands of years ago are frozen in time inside prehistoric layers of permafrost.

Warming temperatures could cause much of the ice to melt and unleash these microbes from their frosty prisons. Once free, unknown pathogens could infect humans or other animals.