The origins of a deadly fungus, which for decades has contributed to a global decline of numerous amphibian populations, has been traced to the Korean peninsula, a new study reports. The data provide a more complete picture of how the fungus spread from region to region, and underscore how, over the past century, human trade of amphibian species has accelerated the spread of the disease. The fungus Batrachochytrium dendrobatidis causes a deadly disease called chytridiomycosis in amphibians. It was first identified in the 1970s, at which point it was increasingly detected in regions around the world, on nearly every continent. However, decades after B. dendrobatidis was first recognized, the geographic origin of the pathogen and timing of its worldwide expansion remain hotly contested, due to inconsistent results from previously studies. To resolve these inconsistencies, Simon O'Hanlon et al. isolated and genetically sequenced 177 samples of B. dendrobatidis across regions, combining their new data with previously published genomes. The data reveal that all strains share the most overlap with a strain called BdASIA-1, found on the Korean peninsula, which suggests that the pathogen originated there. Analysis of the various B. dendrobatidis strains and their relatedness suggests that the pathogen likely arose around the early 20th century, which coincides with the global expansion in amphibian trade (for exotic pet, medical, and food purposes), the authors note; indeed, they identified 10 events where traded amphibians were infected. Further investigation revealed that some strains are more virulent than others, yet population-level outcomes are also context-dependent, the authors report. Karen Lips provides more context in a related Perspective.