Definition of Blastomycosis

Blastomycosis is an infection caused by the fungus Blastomyces. The fungus lives in the environment, particularly in moist soil and in decomposing organic matter such as wood and leaves. In the United States, Blastomyces mainly lives in the midwestern, south-central, and southeastern states, particularly in areas surrounding the Ohio and Mississippi River valleys, the Great Lakes, and the Saint Lawrence River.^1,2 The fungus also lives in Canada,^3-4 and a few blastomycosis cases have been reported from Africa⁵ and India.⁶

People can get blastomycosis after breathing in the microscopic fungal spores from the air, often after participating in activities that disturb the soil. Although most people who breathe in the spores don’t get sick, some of those who do may have flu-like symptoms. In some people, such as those who have weakened immune systems, the infection can become severe, especially if it spreads from the lungs to other organs.