human blastomycosis surveillance in minnesota,1999-2010 carrie klumb 1,2, kirk smith 1, joni...
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Human Blastomycosis Surveillance in Minnesota,1999-2010
Carrie Klumb1,2, Kirk Smith1, Joni Scheftel1
1Minnesota Department of Health2CSTE/CDC Applied Epidemiology Fellowship
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
Background (cont.)• Infection occurs through inhalation of airborne
spores from disturbed soil
• Approximately 50% of infections asymptomatic or resolve spontaneously
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%
Blastomycosis Endemic Regions of North America (in brown)
Fang et al. Radiographics 2007;27:641-655.
Study Objective
Review surveillance data from 1999 to 2010 to better describe the burden and epidemiology of blastomycosis in Minnesota
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
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
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
• 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
Demographic Characteristics of Human Blastomycosis Cases, Minnesota, 1999-2010
(n=371)
Age Group (yrs) No. (%)
0-9 5 ( 1)
10-19 42 (11)
20-29 44 (12)
30-39 66 (18)
40-49 73 (20)
50-59 68 (18)
60-69 26 ( 7)
≥70 43 (12)
56%
Demographic Characteristics of Human Blastomycosis Cases, Minnesota, 1999-2010
Race (n=305) No. (%)% MN
Population
White 256 (84) 85
American Indian 23 ( 8) 1
Black 12 ( 4) 5
Asian 12 ( 4) 4
Other 2 (0.7) 2
Ethnicity (n=201) No. (%)% MN
Population
Non-Hispanic 190 (95) 95
Hispanic 11 ( 6) 5
Symptoms Reported by Cases, Minnesota, 1999-2010 (n=371)
Symptom No. (%)
Cough 258 (70)
Fatigue 229 (62)
Fever 210 (57)
Weight Loss 175 (47)
Night Sweats 161 (43)
Chest Pain 157 (42)
Headache 113 (30)
Skin Sores 91 (25)
Cough with Blood 68 (18)
Clinical Characteristics of Human Blastomycosis Cases, Minnesota, 1999-2010
Characteristic No. (%)
Disease Location n=339
Pulmonary 229 (68)
Disseminated 81 (24)
Extra-pulmonary* 29 ( 9)
*Typically a soft tissue infection following a wound
Clinical Characteristics of Human Blastomycosis Cases, Minnesota, 1999-2010
Characteristic No. (%)
Diagnosis Method n=371
Culture 304 (82)
Smear 142 (38)
Histopathology 54 (18)
Urine Antigen 19 ( 5)
Clinical Characteristics of Human Blastomycosis Cases, Minnesota, 1999-2010
Treatment Type n=314
Antifungals
Itraconazole221 (79)
Amphotericin B51 (18)
Fluconazole11 ( 4)
Voriconazole5 ( 2)
Other Antifungals 7 ( 5)
Antibiotics Only14 ( 5)
Surgical Removal 2 ( 1)
Hospitalized Cases
Fatal Casesn=39
Non-fatal Casesn=205 p-value
No. UnderlyingConditions (%)
15 (38) 52 (25) 0.09
Days hospitalized,median (range)
9
(3 to 48)
7
(1 to 137)0.03
Days admission to testing, median (range)
4
(0 to 32)
1
(0 to 60)0.02
Number of Blastomycosis Cases in Minnesota by Year of Diagnosis,
1999-2010 (n=371)
3133
3028
36
2825
23
33 3335 36
0
5
10
15
20
25
30
35
40
1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010
Year of Diagnosis
No
. of
Ca
ses
Human Blastomycosis Cases by Month of Onset, Minnesota, 1999-2010 (n=324)
20
32
18
27
19
34
24
39
28
38
25
20
0
5
10
15
20
25
30
35
40
45
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
No
. of
Ca
ses
Month of Onset
Human Blastomycosis cases by Season of Onset, Minnesota, 1999-2010 (n=324)
65
77
105
77
0
20
40
60
80
100
120
Spring Summer Fall Winter
No
. of
Ca
ses
Season of Onset
Mar-May Jun-Aug Sept-Nov Dec-Feb
• 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.)
Human Blastomycosis Cases by Probable County of Exposure, 1999-2010 (n=237)
Itasca
St. Louis
Chisago
Washington
Beltrami
CassNumber of Cases
0
1
2-7
8-12
13-29
30-69
Human Blastomycosis Incidence,1999-2010 Cases that were Exposed in County of
Residence (n=176)
Incidence per 100,000 person-years
0
0.10-0.58
0.59-1.10
1.20-2.50
2.60-4.62
Cook
Big Stone
Lake of the Woods
Itasca
Minnesota Biomes
Coniferousand Mixed Forest
TallgrassAspen
Parkland
PrairieGrassland
DeciduousForest
Minneapolis-St. PaulMetropolitan Area
Modified from Minnesota DNR, http://www.dnr.state.mn.us/biomes/index.html
Exposure Frequency Among Cases(n = 273*)
Exposure/Activity %
Woodcutting 38
Gardening 31
Fishing 31
Excavation 30
Hiking 27
Cabin 26
Hunting 19
Camping 15
*Median number of cases with one or more exposures
• 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 Forest Biome
• Recently more cases along St. Croix River bordering Wisconsin
Discussion
Minnesota Biomes
Coniferousand Mixed Forest
TallgrassAspen
Parkland
PrairieGrassland
DeciduousForest
Chisago and Washington Counties
Modified from Minnesota DNR, http://www.dnr.state.mn.us/biomes/index.html
• 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
• Time from admission to diagnostic testing significantly longer in fatal cases
– delayed diagnosis
• Data suggest early detection is critical in preventing fatal outcome
Discussion
• 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
• Smears give same day results; Blastomyces is pathognomonic
Discussion
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
Acknowledgments
Minnesota Department of Health
Brittani Schmidt
Linda Gabriel
Foodborne, Vectorborne, and Zoonotic Disease Unit
Reporting Health Care Facilities