Information for Healthcare Professionals About Blastomycosis

Clinical Features

Healthcare professionals can use the Clinical Testing Algorithm for Blastomycosis to help guide diagnoses.

Approximately 50% of people infected with blastomycosis remain asymptomatic.1 Symptoms usually start 3 weeks to 3 months after exposure among those who become ill. The clinical presentation of blastomycosis is often non-specific; symptoms may include:2,3

  • Fever
  • Cough
  • Night sweats
  • Myalgia
  • Arthalgia
  • Anorexia
  • Chest pain
  • Fatigue
  • Skin lesions

Acute pulmonary blastomycosis is the most common form of blastomycosis and can progress to acute respiratory distress syndrome (ARDS). Some symptomatic cases will develop extrapulmonary infection, which typically manifests as cutaneous, osteoarticular, genitourinary, or central nervous system disease.4


Blastomycosis is typically acquired via inhalation of airborne conidia. Primary cutaneous blastomycosis is uncommon but can result from traumatic inoculation.11


  • Antigen detection: Enzyme immunoassay (EIA) is typically performed on urine or serum but can also be used on bronchoalveolar lavage fluid. EIA urine antigen tests may have the highest sensitivity of noninvasive tests and the quickest turnaround time. Cross-reactions can occur with histoplasmosis and other fungal diseases.
  • Antibody tests: Antibody tests such as immunodiffusion (ID) and complement fixation (CF) are available but have low sensitivity and specificity. Antibody EIAs have also been developed and have better sensitivity and specificity but can be difficult to interpret. Antibody tests may be a useful adjunct diagnostic test when an antigen test is negative or when trying to differentiate blastomycosis from histoplasmosis (e.g., if done in combination with Histoplasma antibody testing).
  • Culture: Culture is the gold standard for diagnosing blastomycosis. A commercially available DNA probe (AccuProbe, GenProbe Inc.) can be used to confirm. Sensitivity can be low.
  • Microscopy: Microscopy is important for detection of yeast in tissue or respiratory secretions.
  • Polymerase chain reaction (PCR): Blastomyces PCR can be used to confirm culture or histopathologic identification and on blood to detect disseminated disease.


Amphotericin B is recommended for moderate to severe disease, central nervous system disease, and for people who are immunosuppressed or pregnant. Itraconazole is recommended for mild to moderate disease and step-down therapy.

should be considered for certain antifungals, like itraconazole, when treating blastomycosis. For more detailed treatment guidelines, please refer to the Infectious Diseases Society of America’s Clinical Practice Guidelines for the Management of Blastomycosis.

Risk groups

People in endemic areas, particularly those who participate in activities that expose them to soil or plant matter, are the primary risk group. A 2019 report showed that American Indian and Alaska Natives and Asians, Native Hawaiians or other Pacific Islanders had the highest incidence rates among reported cases.13  Immunocompromised persons may be at higher risk for developing severe forms of the disease.12

Etiologic agent

Blastomycosis is caused by the dimorphic fungus Blastomyces. Most blastomycosis infections in the United States are caused by B. dermatitidis or B. gilchristii. Recent infections in the western United States have been attributed to a newly described species B. helicus.5,6

Reservoir and endemic areas

The fungus lives in the environment, most often found in soil and decaying organic matter such as wood or leaves. Endemic areas in the United States include the midwestern, south-central, and southeastern states, particularly areas surrounding the Ohio and Mississippi River valleys, the Great Lakes, the Saint Lawrence River, and the western United States.7,8 Parts of Canada are also endemic, particularly Ontario, Saskatchewan, Quebec, and Manitoba.8 Autochthonous cases have also been reported from Africa9 and India.10

Surveillance and statistics

Blastomycosis is reportable in certain states. Check with your state, local, or territorial public health department for more information about disease reporting requirements and procedures in your area. Get blastomycosis statistics.

  1. Klein BS, Vergeront JM, Weeks RJ, Kumar UN, Mathai G, Varkey B, et al. Isolation of Blastomyces dermatitidis in soil associated with a large outbreak of blastomycosis in Wisconsin. N Engl J Med. 1986 Feb 27;314(9):529-34.
  2. Saccente M, Woods GL. Clinical and laboratory update on blastomycosis. Clin Microbiol Rev. 2010 Apr;23(2):367-81.
  3. Baumgardner DJ, Halsmer SE, Egan G. Symptoms of pulmonary blastomycosis: northern Wisconsin, United States. Wilderness Environ Med. 2004 Winter;15(4):250-6.
  4. Chapman SW, Dismukes WE, Proia LA, Bradsher RW, Pappas PG, Threlkeld MG, et al. Clinical practice guidelines for the management of blastomycosis: 2008 update by the Infectious Diseases Society of America. Clin Infect Dis. 2008 Jun 15;46(12):1801-12.
  5. Brown EM, McTaggart LR, Zhang SX, Low DE, Stevens DA, Richardson SE. Phylogenetic analysis reveals a cryptic species Blastomyces gilchristii, sp. nov. within the human pathogenic fungus Blastomyces dermatitidis. PLoS One. 2013;8(3):e59237.
  6. Schwartz IS, Wiederhold NP, Hanson KE, Patterson TF, Sigler L. Blastomyces helicus, a new dimorphic fungus causing fatal pulmonary and systemic disease in humans and animals in Western Canada and the United States. Clin Infect Dis. 2019 Jan 7; 68(2):188-195.
  7. Furcolow ML, Busey JF, Menges RW, Chick EW. Prevalence and incidence studies of human and canine blastomycosis. II. Yearly incidence studies in three selected states, 1960–1967. Am J Epidemiol. 1970;92(2):121–31.
  8. Tat J, Nadarajah J, Kus JV. Blastomycosis. CMAJ. 2023 Jul 31;195(29):E984.
  9. Cheikh Rouhou S, Racil H, Ismail O, Trabelsi S, Zarrouk M, Chaouch N, et al. Pulmonary blastomycosis: a case from Africa. ScientificWorldJournal. 2008 Nov 2;8:1098-103.
  10. Chakrabarti A, Slavin MA. Endemic fungal infections in the Asia-Pacific region. Med Mycol. 2011 May;49(4):337-44.
  11. Gray NA, Baddour LM. Cutaneous inoculation blastomycosis. Clin Infect Dis. 2002 May 15;34(10):E44-9.
  12. Pappas PG, Threlkeld MG, Bedsole GD, Cleveland KO, Gelfand MS, Dismukes WE. Blastomycosis in immunocompromised patients. Medicine. 1993 Sep;72(5):311-25.
  13. Smith DJ, Williams SL, Endemic Mycoses State Partners Group, Benedict KM, Jackson BR, Toda M. Surveillance for Coccidioidomycosis, Histoplasmosis, and Blastomycosis — United States, 2019. MMWR Surveill Summ 2022;71(No. SS-7):1–14.