title: Seasonal variations in the clinical presentation of pulmonary and extrapulmonary blastomycosis.
abstract: Blastomycosis is a granulomatous infection caused by the thermally dimorphic fungus, Blastomyces dermatitidis, for which seasonal variation has been proposed. We conducted a retrospective review of medical records of 324 patients with blastomycosis in Manitoba and northwestern Ontario. The average age of patients at the time of diagnosis was 39+/-20 (range, 0-85) years. Symptoms referable to blastomycosis were first noted in the autumn and winter (September to February) by 63% of the patients. The seasonal distribution of cases was different for localized pulmonary infection than the disseminated disease (P<0.0001). For localized lung disease, the peak incidence of symptom onset occurred in the autumn, and lowest incidence in the spring; one half (50%) of the patients with diffuse lung disease had onset of symptoms in the spring months and a few (11%) cases occurred during the summer. We noted a distinct seasonal variation in the clinical presentation of blastomycosis. The observed pattern suggests that summer environmental exposure and acquisition of the infection results in an early (1-6 months) localized pneumonia in the majority of cases, followed by later (4-9 months) reactivation or slow progression of asymptomatic infection resulting in isolated extrapulmonary or disseminated hematogenous disease in the minority.
authors.affiliation: Section of Infectious Diseases, Department of Medicine, University of Manitoba, Winnipeg.
authors.forename: R
authors.initials: R
authors.lastname: Bruce Light
authors.forename: Doug
authors.initials: D
authors.lastname: Kralt
authors.forename: John M
authors.initials: JM
authors.lastname: Embil
authors.forename: Elly
authors.initials: E
authors.lastname: Trepman
authors.forename: Lyle
authors.initials: L
authors.lastname: Wiebe
authors.forename: Bill
authors.initials: B
authors.lastname: Limerick
authors.forename: Pete
authors.initials: P
authors.lastname: Sarsfield
authors.forename: Greg
authors.initials: G
authors.lastname: Hammond
authors.forename: Kerry
authors.initials: K
authors.lastname: Macdonald
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001758:Blastomyces / Q000302:isolation & purification*; D001759:Blastomycosis / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000382:microbiology; D016009:Chi-Square Distribution; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008168:Lung / Q000000981:diagnostic imaging / Q000382:microbiology; D008172:Lung Diseases, Fungal / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000382:microbiology; D008297:Male; D008350:Manitoba / Q000453:epidemiology; D008875:Middle Aged; D009864:Ontario / Q000453:epidemiology; D011859:Radiography; D012189:Retrospective Studies; D012621:Seasons; D017678:Sex Distribution