A group at the Institut de Microbiologie de la Mediterranee, Aix Marseille Universite, revived a giant virus that had been embedded in permafrost for approximately 30,000 years. The virus was found in the tundra near East Siberia and is thus named Pithovirus sibericum. It is the latest entry in the class of large viruses called Megaviridae, which are so large that they are visible under an ordinary optical microscope:
P.sibericum is, on the scale of viruses, a giant - it has 500 genes, whereas the influenza virus has only eight.
This particular virus is harmless to humans and animals, but it demonstrates there could be unknown health repercussions as more permafrost thaws as the result of a warming planet.