Blastomycosis Statistics and Maps - Minnesota Dept. of Health

Blastomycosis Statistics and Maps

Blastomycosis is a fungal infection usually acquired by breathing in the spores of the fungus (Blastomycosis dermatitidis) that grows in moist soils, particularly in wooded areas and along waterways. Blastomycosis occurs most often in people living in the central and southeastern United States, particularly in the Mississippi and Ohio River valleys and the Great Lakes 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 (mostly dogs) are more numerous than human cases and the location where the pet was exposed can often be more easily identified.

On this page:
Human Cases
Veterinary Cases
Annual summaries

Human Cases

From 1999 -- 2017, 613 laboratory-confirmed cases of human blastomycosis were reported to MDH. A confirmed case of blastomycosis is defined as a Minnesota resident with (1) a positive Blastomyces culture; (2) Blastomyces organisms visualized in tissue or bodily fluid; or (3) a positive Blastomyces antigen test with compatible clinical symptoms.


Human blastomycosis cases by year in MN 1999-2017

Human Blastomycosis in Minnesota by Year, 1999-2017 (PDF)

On average, 32-33 cases of blastomycosis are reported each year in Minnesota. Approximately 9% of these cases die of blastomycosis.

Human blastomycosis cases in MN by age and gender, 1999-2017

Human Blastomycosis Cases in Minnesota by Age and Gender, 1999-2017 (PDF)

Blastomycosis occurs most frequently in middle-age adults, but cases have been reported in ages from 3 – 93 years. About 70% of all cases are male.

Human blastomycosis cases in Minnesota by month of diagnosis, 1999-2017

Human Blastomycosis Cases in Minnesota by Month of Diagnosis, 1999-2017 (PDF)

Blastomycosis is diagnosed slightly  more often in the fall and early winter. This is likely due to exposure to the soil-borne fungus in the summer, and an incubation period of 1-3 months.

Map of Minnesota blastomycosis cases by County of Residence, 1999-2071

Human Blastomycosis Cases by County of Residence, 1999-2017 (PDF)

In Minnesota, people often live and are diagnosed in a different county than where they were exposed to Blastomyces. Look at the difference between this map and the next. 

Map of human blastomycosis cases in Minnesota by county of exposure, 1999-2017

Human Blastomycosis Cases in Minnesota by Probable County of Exposure, 1999-2017 (PDF)

While most people are exposed in northern counties, or those along the Mississippi or St. Croix Rivers, this map shows that people can be exposed to Blastomyces in many counties across the state.

Veterinary Cases

  • Blastomycosis occurs most commonly in dogs; however cats and horses have also been known to become infected.
  • From 1999-2014, 1,149 laboratory-confirmed cases of veterinary blastomycosis were reported to MDH. A confirmed case is defined as a Minnesota resident animal with: a positive urine or serum antigen test and compatible clinical symptoms (or) B. dermatitidis organisms cultured or visualized from tissue or body fluid.




  • Blastomycosis
    Minnesota Department of Health, Disease Control Newsletter; June 2003: Volume 31, Number 4.

Annual Summary Statistics

Updated Tuesday, 02-Oct-2018 09:59:27 CDT