I work on the fungal pathogen Pseudogymnoascus (Geomyces) destructans, which is the causative agent of the recently emerged bat White-Nose Disease. The pathogen originates in Europe and has been introduced to North America where millions of bats have died following infection since 2006. By using population genetic approaches, I am investigating how bats become infected with this pathogen and am disentangling bat-to-bat infections from environment-to-bat infections. I have found evidence of environmental reservoirs from which bats could become infected and am deepening my understanding of these pathogen reservoirs and their implications for disease management strategies. Additionally, I am examining the distribution of the fungus in its home range (across Europe) as well as its population structure in an aim to better comprehend which factors allowed the introduction to North America and its rapid spread there. I believe that the more knowledge the research community has on the biology of a pathogen and its adaptation to host and environment, the better can the spread and impact of the disease be controlled.