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Human Blastomycosis Surveillance in Minnesota,1999-2010

Human Blastomycosis Surveillance in Minnesota,1999-2010. Carrie Klumb 1,2 , Kirk Smith 1 , Joni Scheftel 1 1 Minnesota Department of Health 2 CSTE/CDC Applied Epidemiology Fellowship. Background. Blastomycosis is caused by the dimorphic fungus Blastomyces dermatitidis

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Human Blastomycosis Surveillance in Minnesota,1999-2010

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  1. Human Blastomycosis Surveillance in Minnesota,1999-2010 Carrie Klumb1,2, Kirk Smith1, Joni Scheftel1 1Minnesota Department of Health 2CSTE/CDC Applied Epidemiology Fellowship

  2. Background Blastomycosis is caused by the dimorphic fungus Blastomyces dermatitidis Growth dependent on weather and environmental factors (e.g., recent rainfall, soil acidity) Fastidious organism Extremely difficult to isolate from the environment

  3. Background (cont.) • Infection occurs through inhalation of airborne spores from disturbed soil • Approximately 50% of infections asymptomatic or resolve spontaneously

  4. Background (cont.) Median incubation period is 45 (range, 21 to 106 days) Acute infections present with sudden fever, cough, and pulmonary symptoms of varying severity National case fatality rate is approximately 5%

  5. Blastomycosis Endemic Regions of North America (in brown) Fang et al. Radiographics 2007;27:641-655.

  6. Study Objective Review surveillance data from 1999 to 2010 to better describe the burden and epidemiology of blastomycosis in Minnesota

  7. Methods Human blastomycosis cases are reportable in Minnesota Passive surveillance using standard report form Each case interviewed by MDH staff regarding health history, symptoms, and potential exposures during 3 months prior to onset Likely county of exposure determined from interview

  8. Methods - Case Definition • A Minnesota resident with either: a) B. dermititidis cultured or visualized from tissue or bodily fluids OR b) A positive urine antigen test for B. dermititidis and compatible clinical symptoms • Case inclusion criteria: cases with a diagnosis date between January 1, 1999 and December 31, 2010

  9. Methods (cont.) • Fatal blastomycosis cases compared to hospitalized non-fatal cases to examine possibility of delayed diagnosis • Descriptive analyses were performed using SAS, version 9.2 • ArcMap version 9.3.1 used to identify highly endemic counties in Minnesota

  10. 389 cases of blastomycosis diagnosed and reported to MDH from 1999 to 2010 Incidence: 0.58 cases/100,000 person-yrs 371 (95%) cases sporadic 71% (n=265) male Median age: 44 yrs (range, 3 to 93 yrs) 31% (90/289) underlying conditions 67% (n=247) hospitalized 11% (n=39) fatal Results

  11. Demographic Characteristics of Human Blastomycosis Cases, Minnesota, 1999-2010 (n=371) 56%

  12. Demographic Characteristics of Human Blastomycosis Cases, Minnesota, 1999-2010

  13. Symptoms Reported by Cases, Minnesota, 1999-2010 (n=371)

  14. Clinical Characteristics of Human Blastomycosis Cases, Minnesota, 1999-2010 *Typically a soft tissue infection following a wound

  15. Clinical Characteristics of Human Blastomycosis Cases, Minnesota, 1999-2010

  16. Clinical Characteristics of Human Blastomycosis Cases, Minnesota, 1999-2010

  17. Hospitalized Cases

  18. Number of Blastomycosis Cases in Minnesota by Year of Diagnosis, 1999-2010 (n=371) No. of Cases Year of Diagnosis

  19. Human Blastomycosis Cases by Month of Onset, Minnesota, 1999-2010 (n=324) No. of Cases Month of Onset

  20. Human Blastomycosis cases by Season of Onset, Minnesota, 1999-2010 (n=324) No. of Cases Sept-Nov Mar-May Dec-Feb Jun-Aug Season of Onset

  21. 237 (64%) cases had probable county of exposure in Minnesota 176 (74%) of those cases exposed in county of residence 33 (9%) cases likely exposed outside of Minnesota 101 (27%) cases had unknown county of exposure Results (cont.)

  22. Human Blastomycosis Cases by Probable County of Exposure, 1999-2010 (n=237) Beltrami St. Louis Itasca Number of Cases Cass 0 1 2-7 Chisago Washington 8-12 13-29 30-69

  23. Human Blastomycosis Incidence,1999-2010 Cases that were Exposed in County of Residence (n=176) Lake of the Woods Cook Itasca Incidence per 100,000 person-years 0 Big Stone 0.10-0.58 0.59-1.10 1.20-2.50 2.60-4.62

  24. Minnesota Biomes Tallgrass Aspen Parkland Coniferousand Mixed Forest Minneapolis-St. Paul Metropolitan Area Prairie Grassland Deciduous Forest Modified from Minnesota DNR, http://www.dnr.state.mn.us/biomes/index.html

  25. Exposure Frequency Among Cases(n = 273*) *Median number of cases with one or more exposures

  26. Statewide incidence of 0.58 cases per 100,000 person-years Ranges from 0 to 4.6 cases per 100,000 person-years Northeast and North central part of the state most endemic Coniferous and Mixed ForestBiome Recently more cases along St. Croix River bordering Wisconsin Discussion

  27. Minnesota Biomes Tallgrass Aspen Parkland Coniferousand Mixed Forest Chisago and Washington Counties Prairie Grassland Deciduous Forest Modified from Minnesota DNR, http://www.dnr.state.mn.us/biomes/index.html

  28. Majority of cases are male and between 30 and 59 years of age Possibly due to gender-specific activities American Indians affected by blastomycosis more than other minority groups. However, higher populations in endemic region Case-control study necessary to better answer these questions and determine specific risk factors Recent IRB approval Discussion

  29. Time from admission to diagnostic testing significantly longer in fatal cases delayed diagnosis Data suggest early detection is critical in preventing fatal outcome Discussion

  30. Blastomycosis difficult to diagnosis Rare Symptoms begin as non-specific respiratory illness Often confused with bacterial pneumonia Most common diagnosis method is culture but takes 3 to 4 weeks Contributes to delay in diagnosis Discussion

  31. Smears give same day results; Blastomyces is pathognomonic Discussion

  32. Conclusion The association between delayed diagnosis and case fatality indicate that increased awareness among clinicians and the public could lead to earlier detection and treatment, and reduced mortality due to blastomycosis

  33. Acknowledgments Minnesota Department of Health Brittani Schmidt Linda Gabriel Foodborne, Vectorborne, and Zoonotic Disease Unit Reporting Health Care Facilities

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