Blastomycosis: Key information for health care practitioners

Advisory Alert

June 6, 2024

*Cette information est seulement disponible en anglais.

To: Local Health System Partners


The fungus that causes blastomycosis infection is endemic to the Sudbury and Manitoulin Districts. In 2023, 10 confirmed cases of blastomycosis were diagnosed in Public Health Sudbury & Districts’ service area. We are reminding health care practitioners that diagnostic vigilance is recommended. Given that delays in diagnosis can contribute to illness and death, clinicians should consider blastomycosis in their differential diagnoses of lung, skin, and bone infections—particularly if the patient does not respond to conventional antimicrobial drug therapy.

Cause: Blastomycosis is caused by Blastomyces dermatitidis, a fungus found in acidic, warm, moist soil, especially in wooded areas along waterways such as lakes or rivers. Exposure is by inhalation of airborne spores or by the fungus entering a lesion on the skin.

Incubation period: Symptoms may appear between 3-15 weeks after initial exposure. In Ontario, exposure most often occurs in the summer and fall months as the outdoor activities that would expose an individual usually occur during that time of year. Anyone is susceptible to infection and immunocompromised individuals are more likely to suffer severe illness.

Clinical manifestations: Most patients will suffer fever, chills, and coughing, but clinical manifestations can include more severe pulmonary, cutaneous, and disseminated disease (skin, bones, joints, genitourinary tract). Untreated disseminated or chronic pulmonary blastomycosis can be fatal. Detailed symptomology can be found at the Ministry of Health’s Case Definitions and Disease Specific Information (PDF), The Control of Communicable Diseases Manual, or The Red Book.

Testing: Diagnostic testing is by culture and microscopy of samples from affected organs, and may includes samples of sputum, tracheal aspirates, cerebrospinal fluid, urine, and biopsies of cutaneous lesions. Please refer to Public Health Ontario for specific submission information.

Treatment: Treatment with oral itraconazole or fluconazole is recommended for cases with mild or moderate blastomycosis infections. Amphotericin B is indicated in severe or disseminated infection. The suggested course of therapy is six months. (2)(3)

Information for patients: Information regarding blastomycosis, higher risk activities, and preventative measures can be found on our website at

Blastomycosis is a ‘Disease of Public Health Significance.’ Cases of blastomycosis must   be reported to the Medical Officer of Health by the next business day.

Original Signed By

Mustafa Hirji, MD, MPH, FRCPC
Acting Medical Officer of Health and Chief Executive Officer

NOTE: All Advisory Alerts are found on our website.


  1. Health Protection and Promotion Act. Ontario Regulation 135/18; Designation of Diseases.
  2. Committee on Infectious Diseases. Red Book: 2009 report of the Committee on Infectious Diseases. 28th Ed. American Academy of Pediatrics.
  3. Control of Communicable Disease Manual. 20th Ed. Heymann, David L.

This item was last modified on June 6, 2024