About Blastomycosis - Minnesota Dept. of Health

About Blastomycosis

Blastomycosis is a rare fungal infection usually acquired by breathing in the spores of the fungi Blastomyces dermatitidis or Blastomyces gilchristii. These fungi can be found 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 the mid-western United States. In Minnesota, blastomycosis is most common in northeastern counties, but can occur throughout the state.

In addition to surveillance for cases in humans, the Minnesota Department of Health and the Board of Animal Health also track blastomycosis cases in animals. This allows us to more accurately outline areas in the state where the disease is found. More animals are affected each year than humans, and the location where the animal was exposed to the fungus is often identified more easily.

On this page:
Duration of Illness
Fact Sheet


  • Blastomycosis is usually caused by inhaling airborne spores from contaminated soil into the lungs. Spores are more likely to be airborne after contaminated soil is disturbed by activities such as excavation, construction, digging, or wood clearing.
  • Very rarely, the fungus can infect an open skin wound and cause infection in just that area of the body.
  • Blastomycosis is not spread person-to-person or animal-to-person.


  • Symptoms of blastomycosis may include:
      • Cough, or cough with blood
      • Fever
      • Shortness of breath
      • Chills and/or night sweats
      • Fatigue
      • Weight loss and poor appetite
      • Joint or bone pain
      • Back or chest pain
      • Skin sores that don’t heal
  • Many patients are first diagnosed with bacterial pneumonia because the symptoms are similar. 

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, central nervous system, or genitourinary system).

Duration of Illness

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


  • Blastomycosis may be diagnosed by:
    • Culture (Blastomyces species can be isolated from saliva, respiratory samples, lung biopsies, skin, or other infected tissues)
    • Cytology smear (direct microscopic identification of broad-based budding yeast)
    • Histopathology of surgical biopsies
    • Urine antigen test or serum antigen test
    • Serum antibody test (less reliable)
  • Your doctor may also ask about your travel history, outdoor activities, or the environment around your home to help determine if you might have been exposed to Blastomyces spores.  


  • Blastomycosis can be treated with anti-fungal medications, which are usually continued for at least 6 months.
  • Antibiotics designed for bacteria do not work against blastomycosis.
  • Specific questions about treatment should be discussed with your health care provider.


  • Unfortunately, there are no known practical measures for the prevention of blastomycosis.
  • There are currently no methods to test soil for the presence of Blastomyces species.
  • Illness caused by blastomycosis can be minimized by early recognition and appropriate treatment of the disease. Awareness of the disease by both the public and health care providers is the key to early diagnosis.

Fact Sheet

Updated Thursday, 29-Sep-2022 12:00:11 CDT