B lastomyces dermatitidis, a dimorphic fungus, causes a localized or disseminated pyogranulomatous fungal infection called blastomycosis. Various descriptive studies have shown predominantly pulmonary, skin, bone, and genitourinary involvement (1). The clinical spectrum of blastomycosis is wide, ranging from subclinical infection to critical cases of acute respiratory distress syndrome. Retrospective studies conducted in recent years have shown an increased incidence of blastomycosis in both Canada and the United States (2-5). Blastomycosis is endemic to the St. Lawrence River Valley; a study that focused on the incidence of blastomycosis in the province of Quebec, Canada (6), showed an increasing incidence from 1988 to 2011. Similar trends have been observed in several regions in the United States (7), although the underlying causes are poorly understood. The absence of robust reporting and lack of reportability in many jurisdictions may hamper the ability to know whether cases are increasing more broadly. Some authors suggested a possible relationship with certain climatic factors (3,8). In the wake of the increased incidence of blastomycosis in Quebec, clinicians have observed a possible worsening of the disease severity in patients, with occasional deaths.This study aimed to assess temporal changes in the severity and mortality of blastomycosis in Quebec and to identify risk factors for blastomycosis-related deaths. In Quebec, all suspected B. dermatitidis isolates are sent for molecular species confi rmation at