The location in nature is most often determined by the occurrence of disease. There is no skin test as with histoplasmosis which makes it difficult to determine who has been exposed to B. dermatitidis . Lab experiments have found it is very sensitive to drying, although conidia release only when wetted. Reported cases of blastomycosis have occurred after rain of foggy weather. One theory states that B. dermatitidis cannot compete with the normal flora and can only grow in restricted environments.
Distribution is worldwide, primarily in North America and Africa.
Endemic areas in the U.S. include the midwest, eastern coast, and along the Mississippi and Namekagon Rivers. There have been several localized epidemics of blastomycosis. Out of the 12 outbreaks, only 2 had positive isolations. Blastomycosis is not a disease that is required to be reported to the Center for Disease Control on a national scale. However, it was a reportable disease from 1986 -1995 in Wisconsin after 2 human outbreaks in 1985.