Abstract
Histoplasma capsulatum is a pathogenic dimorphic fungus with evolving epidemiology. Initially described as endemic to the Ohio and Mississippi river valleys, the infection now regularly occurs in central and eastern United States, with cases reported across the entire country. Transmission happens via inhalation of conidia during activities that disturb fungal hyphae. Sporadic cases related to individual exposures now outnumber work-related outbreak cases in the United States. We describe 2 fatal cases of histoplasmosis in Rochester, New York, associated with exposure to bat guano as a fertilizer for cannabis cultivation, including 1 case in which it was commercially obtained.