Indeed, despite being frozen for over 30,000 years, Pithovirus sibericum still packs a punch: a simple thawing procedure allowed it to infect a throng of unsuspecting single-cell organisms for the first time in thousands of years. And given that climate change is already causing the ground to thaw in regions such as the Arctic and parts of Alaska, scientists fear that this lab experiment could eventually take to the field, leading to the spontaneous revival of ancient and unknown viruses. The discovery puts the concept of viral disease eradication in a bit of a jam, says Jean-Michel Claverie, lead author of the study and evolutionary biologist at Aix-Marseille University, because it means that there could be a slew of eradicated viruses — viruses such as smallpox, which caused its last infection in 1977, and the livestock disease rinderpest — laying dormant deep within the Earths oldest frozen soil layers. Warm temperatures can prompt ancient frozen giants to infect anew