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Background. Blastomycosis is a potentially life-threatening infection caused by the soil-based dimorphic fungus Blastomyces dermatitidis, which is endemic throughout much of the Midwestern United States. We investigated an increase in reported cases of blastomycosis that occurred during 2009–2010 in Marathon County, Wisconsin. Methods. Case detection was conducted using the Wisconsin Electronic Disease Surveillance System (WEDSS). WEDSS data were used to compare demographic, clinical, and exposure characteristics between outbreak-related and historical case patients, and to calculate blastomycosis incidence rates. Because initial mapping of outbreak case patients’ homes and recreational sites demonstrated unusual neighborhood and household case clustering, we conducted a 1:3 matched case-control study to identify factors associated with being in a geographic cluster. Results. Among the 55 patients with outbreak-related cases, 33 (70%) were hospitalized, 2 (5%) died, 30 (55%) had cluster-related cases, and 20 (45%) were Hmong. The overall incidence increased significantly since 2005 (average 11% increase per year, P< .001), and incidence during 2005–2010 was significantly higher among Asians than non-Asians (2010 incidence: 168 vs 13 per 100 000 population). Thirty of the outbreak cases grouped into 5 residential clusters. Outdoor activities were not risk factors for blastomycosis among cluster case patients or when comparing outbreak cases to historical cases. Conclusions. This outbreak of blastomycosis, the largest ever reported, was characterized by unique household and neighborhood clustering likely related to multifocal environmental sources. The reasons for the large number of Hmong affected are unclear, but may involve genetic predisposition.

Septic systems that are built in compliance with regulations are generally not expected to be the cause of groundwater borne disease outbreaks, especially in areas with thick vadose zones. However, this case study demonstrates that a disease outbreak can occur in such a setting and outlines the combination of epidemiological, microbiological, and hydrogeological methods used to confirm the source of the outbreak. In early June 2007, 229 patrons and employees of a new restaurant in northeastern Wisconsin were affected by acute gastroenteritis; 6 people were hospitalized. Epidemiological case-control analysis indicated that drinking the restaurant's well water was associated with illness (odds ratio = 3.2, 95% confidence interval = 0.9 to 11.4, P = 0.06). Microbiological analysis (quantitative reverse transcription-polymerase chain reaction) measured 50 genomic copies per liter of norovirus genogroup I in the well water. Nucleotide sequencing determined the genotype as GI.2 and further showed the identical virus was present in patrons' stool specimens and in the septic tank. Tracer tests using dyes injected at two points in the septic system showed that effluent was traveling from the tanks (through a leaking fitting) and infiltration field to the well in 6 and 15 d, respectively. The restaurant septic system and well (85-m deep, in a fractured dolomite aquifer) both conformed to state building codes. The early arrival of dye in the well, which was 188 m from the septic field and located beneath a 35-m thick vadose zone, demonstrates that in highly vulnerable hydrogeological settings, compliance with regulations may not provide adequate protection from fecal pathogens.

We conducted a retrospective study of Salmonella Newport infections among Wisconsin residents during 2003-2005. Multidrug resistance prevalence was substantially greater in Wisconsin than elsewhere in the United States. Persons with multidrug-resistant infections were more likely than persons with susceptible infections to report exposure to cattle, farms, and unpasteurized milk.

This report describes the investigation of a ground-beef-associated outbreak that involved five genetically distinct patient strains of Escherichia coli O157:H7. Human and product isolates were evaluated by pulsed-field gel electrophoresis (PFGE) with two endonucleases. The multiple-strain etiology of this outbreak underscores the importance of isolating and evaluating multiple colonies from outbreak-related products and comparing two endonuclease PFGE patterns of all product and human isolates identified during outbreak periods. This investigation emphasizes the importance of interviewing all confirmed and suspected case patients during the outbreak period, regardless of the PFGE pattern of their isolate, to confirm or rule out an epidemiologic link to the outbreak.

Arcobacter species, primarily Arcobacter butzleri, are widely distributed among animals, infrequently isolated from humans, and previously not associated with outbreaks of foodborne illness. We report results of an investigation of a foodborne outbreak that occurred among attendees of a wedding reception in Wisconsin, United States, and was likely caused by A. butzleri.We conducted a case-control study among reception attendees and a laboratory investigation to determine the extent, source, and cause of the outbreak. A clinical case was defined as diarrhea in an attendee with illness onset ≤7 days following the wedding reception.The case-control study included 47 of 51 case patients and 43 non-ill attendees. Results demonstrated that consuming broasted chicken was the only factor significantly associated with illness (odds ratio 10.51; 95% confidence interval 1.28, 476.4). Five patients provided stool specimens. Comprehensive culture and polymerase chain reaction (PCR) testing did not detect common bacterial or viral pathogens. Subsequent testing with PCRs targeting 16S/23S rDNA of the three most clinically relevant Arcobacter spp. and the rpoB/C gene of A. butzleri provided products confirmed as A. butzleri (four patients) and A. cryaerophilus (one patient) by sequence analysis.The results of this investigation suggest that A. butzleri should be considered an agent that can cause outbreaks of foodborne illness. Rigorous investigation of outbreaks of undetermined etiology is valuable for incrementally increasing our understanding of emerging agents causing foodborne illnesses.

Background: Blastomycosis is a potentially fatal infection caused by the fungus Blastomyces dermatitidis. During January 1 through March 5, 2006, twenty-one laboratory confirmed cases of blastomycosis were reported among residents of an endemic area in north-central Wisconsin; a striking increase compared with previous years. The objective of the study was to determine if an observed increase in blastomycosis among residents of an urban area in north-central Wisconsin was caused by a point-source exposure and to identify its source. Methods: We compared epidemiologic features, and signs and symptoms of B. dermatitidis infection among 46 historic (1999–2005) and 21 possible outbreak case patients. In addition, a case-control study was conducted to compare risk factors of the outbreak case patients with those of 64 age, gender, and geographically-matched control subjects. We conducted site inspections, evaluated meteorological data, genetically compared outbreak and non-outbreak isolates, and attempted environmental detection of B. dermatitidis using polymerase chain reaction, in vitro isolation, and in vivo isolation by tail vein injection of mice. Results: The unusual risk profile of this outbreak included: residence within non-rural city limits with limited time spent outdoors and an equivalent gender ratio and young median age among case patients consistent with common source rather than unrelated exposures. Thirteen of fourteen outbreak-associated clinical isolates of B. dermatitidis clustered in the same genetic group by PCR-RFLP analysis. Inspections near the cluster center suggested a yard waste collection site as the probable exposure source. B. dermatitidis nucleic acid was detected in one of 19 environmental samples. Environmental and meteorological conditions and material management practices were identified that may have facilitated growth and dispersal of B. dermatitidis conidia near this residential area. Conclusions: Results of our investigation of this large non-rural outbreak of blastomycosis suggest bioaerosol hazards may exist near yard waste collection and composting facilities, especially where pine tree litter is present, in B. dermatitidis endemic areas.

Background. Escherichia coli O157:H7 infection often causes hemorrhagic colitis and hemolytic uremic syndrome. Methods. In 2006, the Wisconsin Division of Public Health and the Wisconsin State Laboratory of Hygiene, in cooperation with other local, state, and federal partners, investigated an outbreak of E. coli O157: H7 infection. Results. In September 2006, the Wisconsin Division of Public Health and the Wisconsin State Laboratory of Hygiene were able to link geographically dispersed E. coli O157: H7 isolates recovered from the stool samples of ill persons, all of which had the same pulsed-field gel electrophoresis pattern (i.e outbreak pattern). Investigators conducted a case-control study with control subjects (n = 86) matched to case patients (n = 49) by age, sex, and residential location. All case patients' onsets of illness occurred during the period from 20 August through 14 September 2006. Illness was associated with spinach consumption (matched odds ratio, 82.1; 95% confidence interval, 14.7 to >1000). Of the 49 case patients, 26 (53%) recalled eating brand A spinach. On multibrand analysis, only brand A was associated with illness (undefined matched odds ratio; 95% confidence interval, 6.8-infinity). Wisconsin's agriculture laboratory isolated E. coli O157:H7 with the outbreak pattern from spinach in 2 brand A packages, both produced on 15 August 2006. Conclusions. The rapid multijurisdictional epidemiologic and laboratory response, including timely pulsed-field gel electrophoresis pattern analysis and PulseNet posting, facilitated prompt voluntary recall of brand A spinach.

During September 1999, a multistate outbreak of Salmonella serovar Muenchen infection associated with eating raw alfalfa sprouts was identified in Wisconsin. Despite use of a calcium hypochlorite sanitizing procedure to pretreat seeds before sprouting, at least 157 outbreak-related illnesses were identified in seven states having sprouters who received alfalfa seed from a specific lot. The continued occurrence of sprout-related outbreaks despite presprouting disinfection supports the concern that no available treatment will eliminate pathogens from seeds before sprouting and reinforces the need for additional safeguards to protect the public. A lack of consumer knowledge regarding exposure to sprouts documented in this investigation suggests that more-targeted outreach to high-risk individuals may be needed to reduce their risk.