Blastomycosis in urban southeastern Wisconsin.

Purpose: A previous study revealed a non-random distribution of blastomycosis cases by home site in urban Milwaukee County. This study was conducted to determine the proportion of cases with likely exposures solely in urban areas.

Methods: Records of 68 urban southeastern Wisconsin individuals, including 45 residents of Milwaukee, 19 from suburban Milwaukee County, and 4 from outside Milwaukee County, diagnosed with blastomycosis between January 2002 and July 2007 were studied using medical record reviews, case reports, and telephone interviews. Geographic Information Systems (GIS) proximity analysis was then used to compare the distance between case and control home sites to environmental risk factors.

Results: Of patients reporting their exposure history, 41 of 49 (84%) participated in outdoor work or leisure activities, and 12 of 47 (26%) engaged in fishing, hunting, camping, or hiking. Of the urban cases, 64 occurred among Milwaukee County residents; of those, 25 of 49 (51%) denied traveling, which suggests local urban exposure, and 8 of 11 (73%) specifically recalled urban waterway exposure prior to diagnosis. The 45 Milwaukee cases were concentrated on the north side of town and were closer to inland waterways than a random sample of 6528 controls (median 690 versus 1170 meters; P=0.003), but not closer to parks.

Conclusion: Southeastern Wisconsin residents may acquire blastomycosis solely in their local urban area, sometimes without specific outdoor exposures. Proximity to inland waterways is associated with blastomycosis cases in urban areas, similar to rural areas of Wisconsin. Clinicians should include blastomycosis in appropriate differential diagnoses of symptomatic individuals, even in urban residents without travel history or history of significant outdoor exposures.