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. 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. 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. 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. 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. (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