| Summary: | Background: Blastomycosis is a potentially fatal fungal infection contracted by inhalation of Blastomyces spores from the environment. Blastomycosis case occurrence in dogs has been associated with antecedent weather, using 6-month warm and cold periods. Paracoccidioidomycosis in South America has been associated with variations in the Southern Oscillation Index (SOI). A comprehensive human case registry has been kept in Vilas County, Wisconsin, since 1979 (mandatory reporting since 1984). Purpose: Determine the effects of weather parameters on the occurrence of human blastomycosis cases in this highly endemic area; update exposure factors since last report in 1996. Methods: Database review. Chi-squared test was used for categorical data of exposures, comparing 1979-1996 (N=101) vs. 1997-June 2013 (N=95). Linear regression was used to model lagged local weather station data (available 1990-present; N=126) and SOI, North Atlantic Oscillation Index (NAOI) and Wisconsin River water discharge (WRD)data from the adjacent county (all available for 1984-present; N=174), using pulmonary blastomycosis case counts of known onset by 6-month warm (April-September) and cold (October-March) periods. Results: The seasonal distribution of pulmonary cases, 1984-2012, was: winter (N=35 [22%]), spring (40 [25%]), summer (45 [28%]), fall (42 [26%]); P=0.9. Environmental exposures, 1997-June 2013 (mean age 45, 59% male), were: residence < 400 m from waterway (76%), excavation (42%), gardening (31%); none different than 1979-1996. Fishing (23% vs. 37%; P=0.09) and hunting (15% vs. 26%; P=0.13) were less common than 1979-1996 but not significantly different. Overall, 69% of cases recalled some prior soil- disturbing activities. Considering the 6-month warm/cold periods, 19% of variation is explained by a direct relationship with total precipitation two periods prior (P=0.005). There was no association of case occurrence with SOI, NAOI or WRD. The estimated annual incidence of blastomycosis, 1997-present, was 27/100,000 compared to ...
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