Blastomycosis Basics - Minnesota Dept. of Health

About Blastomycosis

Blastomycosis is a fungal infection usually acquired by breathing in the spores of a fungus (Blastomyces dermatitidis) that grows in moist soils, particularly in wooded areas and along waterways. Blastomycosis occurs most often in people living in Ontario, Manitoba, and the south-central, south-eastern, and mid-western United States. In Minnesota, blastomycosis is most common in St. Louis, Itasca, Cass, Beltrami, Washington, and Chisago counties.

In addition to surveillance of cases in humans, the Minnesota Department of Health and the Board of Animal Health are also studying blastomycosis in animals to better define areas in the state where the disease is found. Veterinary cases are more numerous than human cases and the location where the pet was exposed can often be more easily identified.

On this page:
Duration of Illness
Fact Sheets


  • Blastomycosis is caused by inhaling airborne spores into the lungs after contaminated soil is disturbed by activities such as excavation, construction, digging, or wood clearing.
  • You can only get blastomycosis from the fungus that is in soil or spores in the air.
  • It is not spread from person-to-person or from animal-to-person.


  • Symptoms of blastomycosis may include:
    • Fever
    • Cough, or cough with blood
    • Shortness of breath
    • Muscle aches
    • Bone pain
    • Back pain
    • Chest pain
    • Fatigue
    • Weight loss
    • Chills and/or night sweats
    • Skin sores

The time between exposure to the spores and when symptoms develop varies widely, ranging from 21 to 100 days. The signs and symptoms of blastomycosis vary among individuals. About 50% of infections are asymptomatic (person does not develop any symptoms or disease) or are mild and resolve without treatment. Some patients develop a chronic lung infection or the disease can spread to other areas of the body (skin, bones, genitourinary system, or central nervous system).

Duration of Illness

  • The duration of illness caused by blastomycosis varies greatly between patients.


  • Blastomycosis may be diagnosed by:
    • Culture (Blastomyces can be isolated from saliva, bronchial washes, lung biopsies, skin, or other infected tissues)
    • Smear (direct microscopic identification of broad-based budding yeast)
    • Histopathology of surgical biopsies
    • Urine antigen test or serum antigen test (MiraVista laboratories)
    • Radiology (chest X-ray, bone X-ray)
    • Serum antibody test (not generally reliable)

Your doctor may also ask about your history of residence or exposure activities.


  • Blastomycosis can be treated with anti-fungal medications.
    • Anti-fungal treatment is usually continued for 6 months and recovery is usually complete.
  • Antibiotics do not work against blastomycosis.
  • Specific questions about treatment should be discussed with your health care provider.


  • There are no known practical measures for the prevention of blastomycosis.
  • Illness caused by blastomycosis can be minimized by early recognition and appropriate treatment of the disease.

Fact Sheet

Updated Wednesday, 15-Mar-2017 12:29:33 CDT