Chytridiomycosis, a highly virulent fungal amphibian disease, has been linked to the worldwide decline of more than 500 species - including 90 presumed extinctions - over the last 50 years, researchers report. The study, the first to tally the pathogen's global toll, finds that this amphibian panzootic represents the greatest recorded loss of biodiversity attributable to disease. Caused by the fungus Batrachochytrium dendrobatidis (Bd), chytridiomycosis began causing mass amphibian die-off and extinctions nearly 30 years ago, after a pathogenic strain of the chytrid emerged from Asia, likely through the global animal trade. "Despite increasing understanding of the fungus, scientists have only been able to guess at the scale of damage caused by Bd to amphibian populations across the world," largely due to a lack of an appropriate dataset, write Dan Greenberg and Wendy Palen in a related Perspective. Here, Ben Sheele and colleagues use a comprehensive dataset of chytridiomycosis-related amphibian declines worldwide to reconstruct the deadly history of the disease and quantify its impact on global biodiversity. Sheele et al.'s analysis reveals Bd to be among the most destructive invasive species, contributing to the decline of at least 501 amphibian species - 124 of which are suffering severe (>90%) reductions in abundance. While chytridiomycosis-associated die-offs peaked in the 1980s and the number of new population declines have slowed since, the authors warn that there is a continued risk of outbreaks should Bd or other strains become more virulent or spread into new areas. However, while the majority of species are still experiencing continued decline, not all is lost. The authors report evidence of recovery and even the development of host resistance, among some species.