Epidemic of Pulmonary Blastomycosis (Namekagon Fever) in Wisconsin Canoeists

Abstract

Epidemics of pulmonary blastomycosis have rarely been reported. The following epidemic occurred in a Minnesota family and several of their acquaintances after a canoeing trip in northwestern Wisconsin. The common exposure area was most likely a campsite, located along the upper reaches of the Namekagon River. The Namekagon River Valley is a known endemic area of Namekagon fever (blastomycosis) in dogs. Approximately one month after returning home, five of the eight members of the group had positive direct microscopic examinations and cultures of Blastomyces dermatitidis from their sputa, as well as abnormalities on their chest roentgenograms. Among these five patients, four were symptomatic, with fever, cough, and pleuritic chest pain. Of the three others, one had pleuritic chest pain with a transient lung infiltrate, the second was asymptomatic with a transient lung infiltrate, and the third was asymptomatic with a normal chest roentgenogram. Results of acute serologic tests (complement fixation and immunodiffusion) were negative in all five patients evaluated. None of the patients received antifungal therapy. Follow-up five years after the epidemic revealed that all eight were in excellent health, and none had evidence of continuing pulmonary or extrapulmonary disease.