Expanding Epidemiology of Blastomycosis: Clinical Features and Investigation of 2 Cases in Colorado

On the basis of case reports of blastomycosis, Blastomyces dermatitidis is widely accepted to be endemic in the central United States in and around the Ohio and Mississippi River Valleys. Blastomycosis also occurs in parts of Canada and in the southeastern United States. However, there has been no large-scale skin testing, and the environmental range of B. dermatitidis may have been underestimated. We describe 2 immunocompetent patients with blastomycosis acquired while working in the Front Range region of the Rocky Mountains. The patients were coworkers engaged in a prairie dog relocation project. In the course of this work, they had extensive contact with contaminated soil. Significantly above-average rainfall before the exposure may have contributed to favorable conditions for sporulation of the fungus.