Blastomycosis in urban southeastern Wisconsin

Area of Science:

• Medical Mycology
• Infectious Diseases
• Epidemiology

Background:

• A prior study indicated a non-random geographic distribution of blastomycosis cases in urban Milwaukee County.
• Blastomycosis is a fungal infection caused by *Blastomyces dermatitidis*.

Purpose of the Study:

• To determine the proportion of blastomycosis cases with likely exposures solely within urban environments.
• To investigate the association between urban blastomycosis and environmental risk factors.

Main Methods:

• Retrospective review of medical records, case reports, and telephone interviews for 68 urban southeastern Wisconsin individuals diagnosed with blastomycosis (2002-2007).
• Geographic Information Systems (GIS) proximity analysis comparing case home sites to environmental risk factors against a control group.
• Analysis included home site distances to inland waterways and parks.

Main Results:

• Of 49 patients reporting exposure history, 84% participated in outdoor activities, and 26% engaged in fishing, hunting, camping, or hiking.
• Among urban cases, 51% denied travel, suggesting local exposure; 73% recalled urban waterway exposure.
• Milwaukee cases showed a statistically significant proximity to inland waterways (median 690m vs. 1170m; P=0.003) compared to controls, but not to parks.

Conclusions:

• Blastomycosis can be acquired in local urban areas of southeastern Wisconsin, sometimes without specific outdoor exposures.
• Proximity to inland waterways is a significant risk factor for blastomycosis in urban settings, mirroring findings in rural areas.
• Clinicians should consider blastomycosis in urban patients presenting with symptoms, even without travel history or significant outdoor exposure history.