Endemic Mycoses

Updated Maps of Nationwide Incidence

Bringing updated knowledge to diseases with expanding geographic reach and increasing incidence.

Blastomycosis Cases Per 100,000 Person-Years


Leaflet Map tiles by Carto, under CC BY 3.0. Data by OpenStreetMap, under ODbL.
Cases per 100,000 person years
Over 150
50 - 150
25 - 50
1 - 25
0

Dimorphic Mycoses

Histoplasma, Blastomyces, and Coccidiodes: dimorphic fungi classically known as endemic mycoses of the United States based on their respective ecologic niches within defined geographic distributions. But how well do we know these distributions? How have they changed in the decades between 1969, when the last nationwide, patient-centered update to their geographic distributions was conducted, and today?

The maps above were generated using Medicare fee-for-service claims data from the CMS Chronic Condition Warehouse, with a cohort that includes all persons aged 65 year and older from 2007 - 2016, excluding those with solely diagnostic (e.g., radiography) or laboratory claims. The location of a person's residence was considered the geographic location of their dimorphic mycoses diagnosis.

Incidence for each county was reported as the number of cases per 100,000 person-years, with colorization thresholds for incidence rates optimized for visual discrimination.

How have things changed?

Among the Medicare FFS beneficiaries, there were 79,749 histoplasmosis, 37,726 coccidioidomycosis, and 6,109 blastomycosis diagnoses from 2007-2016.

  • 1,971 out of 3,143 counties had >5 incident histoplasmosis diagnoses. 92% (1806/1971) had incidence >100 cases per 100,000PY.
  • 1,602 out of 3,143 counties with >1 blastomycosis diagnosis. 34% (547/1602) had incidence >100 cases per 100,000PY.
  • 839 out of 3,143 counties with >3 coccidioidomycosis diagnoses. 40% (339/839) had incidence >100 cases per 100,000PY.

These distributions of clinically significant incidence rates extend beyond the historical boundaries of each dimorphic mycosis last described in 1969.

Rendering of Histoplasma capsulatum, provided by the CDC Public Health Image Library.

Raising Awareness

Increasing clinician awareness of more widespread distributions of DM is vitally important to prevent delayed or missed diagnoses. Diagnosis is delayed by more than one month in 40% of blastomycosis cases and 46% of coccidioidomycosis cases. Histoplasmosis patients experience an average of a 40-day delay in diagnosis, with over 80% having a healthcare visit representing a missed opportunity for diagnosis. The most common cause of diagnostic delay is attributed to failure to consider DM etiologies.

The geographic distributions of the three dimoprhic mycoses have expanded to regions outside their historical distribution. Acknowledging an expanded geographic distribution for these fungi is important to maintain high clinical suspicion of these pathogens. Dimoprhic mycoses should be considered when there is concern for a fungal infection anywhere in the US in patients with a compatible clinical syndrome, particularly in those who are immunocompromised.