...Permafrost covers a fifth of the Northern Hemisphere, having underpinned the Arctic tundra and boreal forests of Alaska, Canada and Russia for millennia. It serves as a kind of time capsule, preserving ... ancient viruses. \ ...The virus hunter Claverie studies a particular type of virus he first discovered in 2003.... / ...In 2014, he managed to revive a virus he and his team isolated from the permafrost, making it infectious for the first time in 30,000 years by inserting it into cultured cells. ... Precedent for human infection Traces of viruses and bacteria that can infect humans have been...