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  1. 1. MINNESOTA DEPARTMENT OF HEALTH D ISEASE C ONTROL N EWSLETTER Volume 31, Number 4 (pages 29-36) June 2003 West Nile Virus: An Update for Minnesota Medical Providers West Nile virus (WNV) was documented introduced into the United States is not confirmed in 39 states and the District of in Minnesota for the first time in 2002 as known. However, the most likely Columbia; this total included 284 part of an intense national outbreak. The mechanism is that infected mosquitoes fatalities. The median age of WNV Minnesota Department of Health (MDH) or birds were accidentally transported cases was 55 years (range, 1 to 99 is continuing surveillance for this virus in here. years). The median age of fatal WNV 2003. This update describes the 2002 cases was 77 years (range, 19 to 99 outbreak, provides additional information West Nile Virus Transmission Cycle years). By the end of 2002, only Alaska, about WNV, and provides instructions for WNV is maintained and circulated in a Hawaii, Oregon, Nevada, Utah, and submitting clinical specimens from complex cycle involving several species Arizona had not reported WNV activity in suspected WNV and other arboviral of mosquitoes and wild birds. Infected humans, horses, birds, or mosquitoes encephalitis case-patients to the MDH mosquitoes feed on birds, some of (Figure 1). Public Health Laboratory. which act as amplifying hosts for the virus. This cycle continues throughout In 2002, WNV was detected in Minnesota History and Range of West Nile Virus the summer. By mid- to late summer, in humans, horses, birds, and mosqui- WNV was first isolated from a febrile conditions for virus transmission to toes. There were 48 human cases woman living in the West Nile province of mammals have peaked with a large reported from 31 Minnesota counties Uganda in 1937. The virus is in the population of vector-competent infected (Figure 2). Thirty-one (65%) of the 48 family Flaviviridae and the Japanese mosquitoes. In addition, mosquitoes that Minnesota cases were diagnosed with Encephalitis Antigenic Complex (which feed on birds in the spring and early West Nile fever (WNF), the less severe also includes Alfuy, Japanese Encephali- summer are believed to often switch to end of the clinical spectrum, seven tis, Kokobera, Koutango, Murray Valley, mammalian hosts for blood meals later (15%) of the cases had aseptic meningi- Kunjin, St. Louis encephalitis, Stratford, in the summer. It has been hypothesized tis, and nine (19%) had encephalitis. and Usutu viruses). The first recorded that mosquitoes make this switch Acute flaccid paralysis was observed in outbreak occurred in Israel during the because juvenile birds that provided an three (6%) of the cases (two of these 1950s, and WNV is now recognized as easy meal have matured, and birds have three cases also had encephalitis). one of the most widespread flaviviruses. improved defensive behaviors (ruffling of Twenty-seven (56%) cases were Along with its current range in North feathers and twitching) that deter hospitalized; the median duration of America, endemic transmission occurs mosquitoes. It is not known how WNV hospitalization was 8 days (range, 1 to in Africa, Southern Europe, and Western survives northern winters, but it is 56 days). Two hospitalized case- Asia. believed the virus can be maintained in patients were discharged to long-term an area by over-wintering infected adult care facilities. None of the cases was In late summer of 1999, the first domesti- female mosquitoes or chronically fatal. Thirty-two (67%) cases were male cally acquired human cases of West Nile infected resident birds, and/or be and 16 (33%) were female. The median encephalitis in the United States were reintroduced in the spring by migratory age for case-patients was 48 years documented in the New York City area. birds. continued... Concurrently, WNV caused a large epizootic among wild birds (especially The West Nile Virus Outbreak in the American Crows) in the same area. United States and Minnesota, 2002 Inside: Since then, WNV has quickly spread to The WNV outbreak that occurred in the Blastomycosis Surveillance in 44 states and the District of Columbia in United States in 2002 was the largest Minnesota, 1999-2002...................32 the United States, five Canadian prov- outbreak of arboviral disease ever Asthma Action Plan: A Tool for inces, two Mexican states, and the recorded in the Western Hemisphere. Medical Professionals..................36 Cayman Islands. Exactly how WNV was During 2002, 4,156 human cases were
  2. 2. for the majority of WNV transmission to Figure 1. U.S. Counties Reporting Any birds and mammals. However, the exact West Nile Virus Activity, 2002* species of mosquitoes and birds sustaining the virus likely varies by region in the United States. In eastern states and the eastern Midwest (e.g., Illinois, Michigan), especially in large urban areas, the Northern House Mosquito (Culex pipiens) has been implicated as the primary vector of WNV to humans. This mosquito reproduces in small pools of water with high levels of organic pollution, such as those that are often found in urban areas. In states further west, including Minnesota, Culex tarsalis is suspected as being the primary vector of WNV to humans. Culex tarsalis is a known vector of western equine en- cephalitis (WEE) virus. One of six WNV- * From the Centers for Disease Control and Prevention, through MMWR week 53 (ending positive mosquito samples in Minnesota 12/31/2002 - 2,480 counties). Reported and verified through ArboNet as of 1/21/2003. during 2002 was this species. Clinical Presentation of West Nile (range, 4 to 85 years). (Note: for both WNV was first documented in Minnesota Virus Disease national and state case data, the median in a bird that was reported on July 9 in Most human infections with WNV or age was calculated using combined Mille Lacs County. Ultimately, 342 of 790 other arboviruses are asymptomatic. West Nile fever and West Nile menin- birds tested (from 67 counties) in Most clinically apparent WNV infections goencephalitis cases). Minnesota were positive by polymerase are febrile illnesses characterized by chain reaction, immunohistochemistry, headache, stiff neck, myalgia, arthralgia, A majority of human cases occurred at or virus isolation (Figure 2). Fifty-nine and fatigue. Severe symptomatic the end of the summer. Onset dates percent of American Crows and 34% of infections can result in various neuro- ranged from August 7 to September 28; Blue Jays (both in the Corvid family) logic manifestations, ranging from 45 (94%) of the 48 cases had onset from tested by MDH were positive for WNV; aseptic meningitis to fulminant and fatal August 15 to September 24 (Figure 3). these species are most useful in WNV encephalitis. Signs and symptoms may This distribution of onsets is consistent surveillance. Fifty-nine percent of include confusion or other changes in with national data. raptors (i.e., hawks and owls) tested by mental status, nausea, vomiting, MDH were positive. In contrast, 12% of meningismus, cranial nerve abnormali- In addition to mosquito-borne transmis- other bird species (e.g., finches, ties, paresis or paralysis, sensory sion, five other routes of WNV infection sparrows, blackbirds) tested were deficits, altered reflexes, abnormal were documented in the United States positive for WNV. A majority of positive movements, convulsions, and coma. during the 2002 outbreak. At least 20 birds were found within the seven-county West Nile meningitis or encephalitis cases of transfusion-associated WNV Minneapolis-St. Paul metropolitan area; cannot be distinguished clinically from 1 infection were reported. Four cases of however, this was likely due to the large some other central nervous system WNV infection attributed to organ human population reporting birds and the infections. 2 transplantation were reported. One logistic difficulty of transporting birds to case of transplacental WNV transmis- the Minnesota Veterinary Diagnostic Laboratory Testing and Surveillance sion was documented.3 There was one Laboratory (MVDL) for testing from The MDH Public Health Laboratory has case of asymptomatic WNV infection in greater Minnesota. Nationwide, 16,739 an arbovirus testing panel available, and an infant in which the probable route of WNV-positive birds were reported in 42 physicians who see suspected cases of transmission was through breast milk.4 states plus the District of Columbia. arboviral encephalitis are encouraged to In addition, occupational infections in WNV has been found in over 160 submit clinical specimens to MDH for laboratory workers were reported. 5 species of birds in the United States. testing. Several tests for human These additional routes of transmission Dead bird surveillance is still considered samples are available at MDH: accounted for a very small proportion of the most sensitive indicator of virus cases. presence in an area. Serum: • WNV: IgM and IgG antibody capture Nationwide, 14,539 horses tested Twenty-nine species of mosquitoes in EIA. positive for WNV in 2002; of these, 992 the United States have been found to be were from 84 of the 87 Minnesota infected with WNV in field conditions; • LaCrosse encephalitis, eastern equine counties (Figure 2). As in other states, however, not all of these mosquito encephalitis (EEE), WEE, and St. approximately one-third of symptomatic species are able to maintain and Louis encephalitis: Igm IFA. horses were euthanized or died from transmit the virus. It is believed that their WNV infection. Culex genus mosquitoes are responsible continued on page 32 30
  3. 3. Figure 2. Minnesota Counties with West Nile Virus- Positive Humans, Horses, or Birds, 2002 Kittson Roseau 4 Horses 2 Humans 10 Horses Lake of the Woods 2 Horses Marshall Koochiching 9 Horses 2 Horses 1 Bird Beltrami Pennington 8 Horses 1 Human 1 Bird 8 Horses 1 Bird Polk Red Lake St. Louis Lake Cook 1 Human 4 Horses 2 Horses 6 Horses 1 Bird Clearwater 6 Birds 4 Horses 1 Bird Itasca 1 Horse Norman Mahnomen 2 Humans 6 Horses 8 Horses 1 Bird Hubbard Cass 6 Horses 5 Horses Clay Becker 2 Humans 1 Human 26 Horses 17 Horses 10 Birds 1 Bird Wadena Aitkin Carlton 15 Horses Wilkin 1 Horse 3 Horses 1 Bird Crow Wing 1 Human Otter Tail 1 Bird 1 Human 4 Horses 49 Horses 9 Horses Counties with WNV- 3 Birds 4 Birds Positive Humans Pine 2 Horses Mille Lacs 3 Birds Todd Morrison 16 Horses Grant Douglas 29 Horses 1 Human 1 Bird Confirmed Findings 2 Humans 1 Human 14 Horses Kanabec 6 Horses 23 Horses 2 Birds 4 Horses 48 Humans (31 counties) 1 Bird 1 Bird 992 Horses (84 counties) Traverse Benton 342 Birds (67 counties) Stevens 15 Horses 3 Horses 1 Human Pope Stearns 1 Bird Isanti - American Crow (224 ) Big Stone 3 Horses 11 Horses 35 Horses 1 Human - Blue Jay (40) 2 Birds 3 Birds 10 Birds 14 Horses 6 Horses Sherburne 2 Birds - Other/Unknown (78) Chisago 2 Birds 28 Horses Swift Anoka 6 Horses 5 Birds 4 Birds 1 Human 2 Humans 8 Horses 21 Horses 19 Horses 8 Birds Kandiyoh i Meeker Wright 1 Bird 30 Birds Ramsey 1 Human 20 Horses 1 Human Washington 10 Horses 3 Birds 67 Horses 1 Human Chippewa Hennepin 37 Birds Lac Qui Parle 1 Human 4 Birds 4 Birds 4 Humans 1 Human 14 Horses 31 Horses 11 Horses 1 Bird McLeod Carver 87 Birds 2 Birds 3 Humans 2 Humans Renville 10 Horses 15 Horses Yellow Medicine 12 Horses 3 Birds 6 Birds Scott Dakota 6 Horses 2 Birds 1 Bird 1 Human Sib ley 30 Horses 3 Humans 24 Horses 8 Horses 7 Birds 12 Birds 1 Bird Lincoln Lyon Redwood Le Sueur Rice Goodhue 3 Horses 11 Horses 1 Human Nicollet 3 Birds 3 Birds 9 Horses 8 Horses 2 Humans 15 Horses Wabasha Brown 3 Horses 1 Bird 2 Birds 11 Horses 3 Birds 8 Horses 2 Birds 12 Horses 2 Birds 2 Birds 1 Bird Pipestone Murray Cottonwood Watonwan Blue Earth Waseca Steele Dodge Olmsted Winona 15 Horses 19 Horses 13 Horses 1 Human 12 Horses 12 Horses 3 Horses 8 Horses 6 Horses 7 Horses 2 Birds 2 Birds 4 Birds 9 Horses 1 Bird 2 Birds 1 Birds 4 Birds 1 Bird 2 Birds Rock Nobles Mower Jackson Martin Faribault Freeborn Fillmore Houston 1 Human 2 Humans 3 Humans 1 Horse 7 Horses 11 Horses 13 Horses 8 Horses 10 Horses 7 Horses 19 Horses 2 Horses 3 Birds 8 Birds 4 Birds 2 Birds 3 Birds 1 Bird 1 Bird 31
  4. 4. Figure 3. Human West Nile Virus Cases by Illness Onset Date, Minnesota, 2002 (n=48) E ncep hali tis/M en ing itis A c ute Flaccid P aralysis W e s t N ile Fe ve r H os pita liz e d 6 Number of Cases 5 4 3 2 1 6 7 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 A ug us t S e pte m be r O n s e t D a te Cerebrospinal fluid: Many asymptomatic or mildly ill patients the quick links menu at • WNV and other endemic arboviruses: may request arbovirus testing, especially www.health.state.mn.us. If reporting via EIA for IgM and IgG, TaqMan assay if they were bitten by mosquitoes. The the internet is not feasible, dead birds (PCR), Vero cell culture. likelihood of WNV (or other arbovirus) also can be reported by calling (612) infection in these patients is very small, 676-5055 or 1-877-676-5414 (8:00 a.m.- To arrange testing or to report a sus- and MDH does not encourage testing in 4:30 p.m.). The MDH Public Health pected case, call MDH at 612-676-5414 these instances. Laboratory will be testing selected dead or 1-877-676-5414. birds for WNV. MDH investigates all reported cases of The MDH Public Health Laboratory i s arboviral illness to document the clinical For more information about WNV, visit concentrating its WNV testing efforts and details of the case and to determine the MDH website resources on patients who meet any of where patients may have been exposed (www.health.state.mn.us), or call 612- t ef l o i gc i e i : h olwn rtra to virus-infected mosquitoes. MDH also 676-5414 or 1-877-676-5414. works with the Metropolitan Mosquito - presumptive viral encephalitis or Control District to test mosquitoes from References locations where cases may have been 1. Centers for Disease Control and Prevention. aseptic meningitis; Public health dispatch: investigation of blood exposed and from other high-risk areas. transfusion recipients with West Nile virus - fever and headache that warrant a MDH is working with the Minnesota infections. MMWR 2002;51:823. lumbar puncture and/or hospitalization; Board of Animal Health and the University 2. Centers for Disease Control and Prevention. Public health dispatch: West Nile virus of Minnesota College of Veterinary infection in organ donor and transplant or Medicine to test equine samples for recipients — Georgia and Florida, 2002. WNV, WEE, and EEE. MMWR 2002;51:790. 3. Centers for Disease Control and Prevention. - presumed Guillain-Barre syndrome or Intrauterine West Nile virus infection — New acute flaccid paralysis. The most sensitive way to identify WNV York, 2002. MMWR 2002;51:1135-1136. in an area is through wild bird surveil- 4. Centers for Disease Control and Prevention. Collection of acute and convalescent lance. Therefore, Minnesota residents Possible West Nile virus transmission to an infant through breast-feeding —- Michigan, (i.e., approximately 2-4 weeks after the are encouraged to report dead birds 2002. MMWR 2002;51:877-878. acute sample) serum samples is (especially American Crows and Blue 5. Centers for Disease Control and Prevention. strongly encouraged. Jays) to MDH via the internet by access- Laboratory-acquired West Nile virus ing the Dead Bird Reporting Form link on infections — United States, 2002. MMWR 2002;51:1133-1135. Blastomycosis Surveillance in Minnesota, 1999-2002 Background outbreak information, is 45 days (range, Epidemiology of Blastomycosis in Blastomycosis is a systemic mycosis 21 to 106 days). Most infections are Minnesota, 1999-2002 caused by Blastomyces dermatitidis, a asymptomatic or self-limiting. In clinical From 1999, when systematic surveil- dimorphic fungus that exists as a mold cases, acute pulmonary symptoms lance for blastomycosis was instituted in the environment and as a pathogenic ranging from mild to fulminant are the in Minnesota, through 2002, 140 yeast form in the body. Blastomycosis most common manifestation; however, laboratory-confirmed cases of blasto- is endemic in the central and southeast- the infection may disseminate to the mycosis were reported to the Minnesota ern United States, particularly in the skin, bones, genitourinary system, and Department of Health (MDH). A Mississippi and Ohio River valleys and central nervous system (CNS). The confirmed case was defined as a the Great Lakes states. The reservoir is case fatality rate is approximately five Minnesota resident with B. dermatitidis rich, moist soil; transmission occurs percent nationwide. cultured or visualized from tissue or through inhalation of aerosolized conidia body fluid. The 140 reported cases from contaminated soil. The median include 18 cases that occurred during incubation period, based on limited an outbreak of blastomycosis in 32
  5. 5. Mountain Iron, Minnesota in 1999. The distribution of race among the cases skin sores. Sixty-eight (65%) of 104 median annual number of cases from was as follows: white, 85%; Native cases reported weight loss; 61 (59%) 1999 to 2002 was 30.5 (range, 28 to 49 American/Alaskan Native, 8%; Asian/ reported night sweats and chills; 50 cases) (Figure 1). The median annual Pacific Islander, 4%; black, 3%, and (48%) reported headache, and 50 (48%) incidence of blastomycosis statewide other 1%. Seventy-four percent of reported chest pain. Eighty-eight (67%) over the period was 0.6 cases per cases were diagnosed during June of 131 cases were hospitalized for a 100,000 population. St. Louis County through December, with a peak in median of 7 days (range, 1 to 56 days). residents accounted for 42 cases September (Figure 5). There were 11 fatal cases from 1999 to reported to MDH from 1999 to 2002, 2002, resulting in a case fatality rate of followed by Itasca (15), Hennepin (14), Of 115 cases with reported symptom 8%. Cases with an underlying chronic Ramsey (11), Cass (seven), Anoka information, 92 (80%) reported cough, illness were more likely to be fatal (five (five), and Beltrami (five) Counties including 17 (15%) with hemopytsis; 85 of 22 [23%] vs. one of 82 [1%]; relative (Figure 2). The median annual inci- (74%) reported fatigue; 81 (70%) risk, 18.9; 95% confidence interval, 2.3- dence of blastomycosis in St. Louis reported fever, and 29 (25%) reported 153.3; p=0.001). The 22 cases with County residents was 2.7 cases per 100,000 population (range, 1.5 [2002] to 14.0 [1999] per 100,000). The probable Figure 1. Reported Human Cases of Blastomycosis county of exposure to B. dermatitidis in Minnesota by Year, 1999-2002 (n=140) was identified for 89 cases; St. Louis, Itasca, Cass, and Beltrami Counties accounted for 66% of cases (Figure 3). 50 Outbreak cases Sporadic cases Number of Cases The median age of blastomycosis 40 18 cases was 44 years (range, 4 to 83 30 years) (Figure 4). Overall, 67% of cases were male. However, only five 20 (28%) of the 1999 outbreak-associated 31 33 30 28 cases were male. If outbreak cases are 10 excluded, the gender difference among sporadic cases from 1999 to 2002 is 0 more remarkable; 88 (72%) of 122 1999 2000 2001 2002 sporadic cases were male. The Year Figure 2. Number of Human Blastomycosis Cases Figure 3. Number of Human Blastomycosis Cases by County of Residence, 1999-2002 by Probable County of Exposure, 1999-2002 (n=139)* (n=89)* Kittson Roseau Kittson Roseau Lake Lake of the of the Woods Woods Marshall 1 Marshall 3 1 Koochiching St. Louis Koochiching Beltrami Beltrami St. Louis 2 2 5 Pennington Cook Pennington Cook Polk Polk Red Lake Lake Red Lake 4 Lake Clear Itasca Itasca Clear Itasca Water 38 Water 42 1 15 12 Norman Mahnomen Hubbard 15 Norman Mahnomen Hubbard Cass Cass Clay Becker 2 7 7 Clay Becker 2 5 Aitkin Aitkin Wadena Crow Wing Wadena Crow Wing Carlton 3 Carlton 1 1 2 Wilk in Ottertail Ottertail Wilkin 1 3 1 Pine Hennepin Pine Todd Todd Mille Grant Mille Lacs Kanabec 1 Lacs Kanabec Douglas Grant Douglas Morrison Morrison 1 1 No. cases Benton No. cases Benton 4 Traverse Stevens Pope Stearns Isanti 3 1-5 1-5 Traverse Stevens Pope Stearns Isanti Big Stone Big Stone Sherburne 1 Sherburne 6-15 6-15 Chisago 1 Swift Kandiyohi 2 Anoka Chisago Swift Kandiyohi Anoka Meeker Wright 1 5 Wash- ing- >15 Chippewa Meeker Wright Wash- ing- Ra m- ton >15 Chippewa Ram ton Hennepin Hennepin Hennepin Ram- sey 14 sey sey McLeod 1 1 1 2 11 McLeod Lac Qui Parle 1 Lac Qui Parle Renville Carver Renvi lle 1 Carver 3 Yellow Medicine 1 Scott Yel low Medicine 1 1 Scott Dakota Lincoln Lyon Sibley Dakota Sibley Lincoln Lyon Redwood Rice Goodhue Redwood Rice Nicollet Le Goodhue Sueur Nicollet Le Wabasha 1 Sueur 1 Wabasha Brown Brown Waseca 1 Pipestone Murray Cottonwood Watonwan Blue Earth Waseca Steele Dodge Olmsted Winona Pipestone Murray Cottonwood Watonwan Blue Earth Steele Dodge Olmsted 1 1 2 Winona 1 1 2 Rock Nobles Jackson Martin Freeborn Fillmore Houston Faribault Mower Rock Nobles Jackson Martin Faribault Freeborn Mower Fillmore 1 Houston 1 1 1 1 *The probable county of exposure was not determined *The county of residence was unknown for one case. for 51 of the 140 cases reported during 1999-2002. 33
  6. 6. (18%), and owning or visiting a cabin Figure 4. Human Blastomycosis Cases in Minnesota by Age, (18%). 1999-2002 (n=140) 1999 Mountain Iron Outbreak Prior to 1999, the only blastomycosis 40 Median age, 44 years outbreak identified in Minnesota oc- 35 (range, 4-83 years) curred in 1972 in Itasca County.2 In Number of Cases 30 September 1999, a cluster of blastomy- 25 cosis cases was reported from the town of Mountain Iron in St. Louis County. 20 The ensuing investigation involved 15 active surveillance for human and 10 veterinary cases, interviewing and serological screening of town residents, 5 a case-control study to identify risk 0 factors for infection, soil cultures, and a <10 11-20 21-30 31-40 41-50 51-60 61-70 >70 meteorologic review. Age Group (years) A human case was defined as a Mountain Iron resident who had B. dermatitidis cultured or visualized from sputum or bronchial lavage fluid. Figure 5. Human Blastomycosis Cases in Minnesota by Eighteen human cases were identified. Month of Diagnosis, 1999-2002* All lived in a single neighborhood of 25 approximately 200 households. The median age was 38 years (range, 7 to 70 years). Thirteen (72%) cases were 20 female. Ten (56%) were hospitalized, Number of Cases for a range of 1 to 22 days. There were 15 no fatalities. Cases were more likely to report other ill family members (odds 10 ratio, 6.8; p<0.05) and lived closer to a recent new house excavation site than 5 healthy neighborhood controls (p=0.05). Hunting, fishing, hiking on a neighbor- hood trail, gardening, or owning an ill 0 dog were not associated with illness. Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month of Diagnosis A canine case was defined as a dog *Based on 131 cases for which information was available. from Mountain Iron from which B. dermatitidis was cultured or visualized chronic illness included nine with bronchoalveolar lavage fluid (36%), lung from sputum, skin, or bronchial lavage diabetes, three with leukemia, and ten aspirate (12%), or wound exudate fluid; a suspect case had either a with other neoplastic, degenerative, or (12%). Sixteen (13%) cases were chronic cough or non-resolving skin inflammatory disorders. confirmed by histopathology of lymph lesion. Nineteen confirmed and four nodes, lung nodules, or trans-bronchial suspect canine cases lived in the same Seventy-nine (66%) of 119 blastomyco- biopsies. Serology was positive in nine neighborhood as human cases. In this sis cases with reported clinical informa- cases. outbreak, dogs were not useful as tion were limited to pulmonary infection, sentinels because their onsets of illness but in 30 (25%) cases the infection had Eight (8%) of 102 blastomycosis cases were generally concurrent with or after disseminated to skin or soft tissues from 1999 to 2002 had potential human case illness onsets (Figure 6). (68%), bones or joints (16%), the CNS occupational exposures. Six cases (5%), the eye (3%), or other tissues were workers involved with excavation Serologic testing of neighborhood (8%). Ten (8%) cases were categorized and outdoor construction, and two were volunteers by immunodiffusion and as extra-pulmonary only; most of these forestry workers in endemic counties. complement fixation did not identify were localized soft tissue infections Excavation has previously been additional cases. Only two of 11 following a traumatic injury such as a identified as a risk factor for infection.1 culture-confirmed cases and none of puncture wound. The diagnosis was From 1999 to 2002 in Minnesota, 36 the other 157 residents tested devel- confirmed in 112 (90%) of 125 cases by (36%) sporadic blastomycosis cases oped a detectable antibody response. culture of bronchoalveolar lavage fluid reported excavation at or near their These findings illustrated the inad- (42%), sputum (32%), wound exudate residence within 3 months of onset of equacy of available serologic tests for (16%,) or lung aspirate (9%). In 54 illness. This was the most commonly screening or diagnostic purposes. All of (43%) cases, the organism was reported potential risk factor, followed by the human isolates of B. dermatitidis identified in a smear of sputum (41%), woodcutting (29%), hiking (25%), fishing 34