Blastomycosis Mortality Rates, United States, 1990–2010 - Volume 20, Number 11—November 2014 - Emerging Infectious Disease journal - CDC

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Blastomycosis Mortality Rates, United States, 1990–2010 - Volume 20, Number 11—November 2014 - Emerging Infectious Disease journal - CDC

Volume 20, Number 11—November 2014

CME ACTIVITY - Synopsis

Blastomycosis Mortality Rates, United States, 1990–2010

On This Page

• Medscape CME Activity
• Methods
• Results
• Discussion
• Suggested Citation

Figures

• Figure

Tables

• Table 1
• Table 2
• Table 3

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Diana Khuu , Shira Shafir, Benjamin Bristow, and Frank Sorvillo

Author affiliations: University of California, Los Angeles, California, USA (D. Khuu, S. Shafir, F. Sorvillo); Icahn School of Medicine at Mount Sinai, New York, New York, USA (B. Bristow)

Suggested citation for this article

Abstract

Blastomycosis is a potentially fatal fungal infection endemic to parts of North America. We used national multiple-cause-of-death data and census population estimates for 1990–2010 to calculate age-adjusted mortality rates and rate ratios (RRs). We modeled trends over time using Poisson regression. Death occurred more often among older persons (RR 2.11, 95% confidence limit [CL] 1.76, 2.53 for those 75–84 years of age vs. 55–64 years), men (RR 2.43, 95% CL 2.19, 2.70), Native Americans (RR 4.13, 95% CL 3.86, 4.42 vs. whites), and blacks (RR 1.86, 95% CL 1.73, 2.01 vs. whites), in notably younger persons of Asian origin (mean = 41.6 years vs. 64.2 years for whites); and in the South (RR 18.15, 95% CL 11.63, 28.34 vs. West) and Midwest (RR 23.10, 95% CL14.78, 36.12 vs. West). In regions where blastomycosis is endemic, we recommend that the diagnosis be considered in patients with pulmonary disease and that it be a reportable disease.

Blastomycosis is a systemic infection caused by the thermally dimorphic fungus Blastomyces dermatitidis that can result in severe disease and death among humans and animals. B. dermatitidis is endemic to the states bordering the Mississippi and Ohio Rivers, the Great Lakes, and southern Canada; it is found in moist, acidic, enriched soil near wooded areas and in decaying vegetation or other organic material (1). Conidia, the spores, become airborne after disruption of areas contaminated with B. dermatitidis. Infection occurs primarily through inhalation of the B. dermatitidis spores into the lungs, where they undergo transition to the invasive yeast phase. The infection can progress in the lung, where the infection may be limited, or it can disseminate and result in extrapulmonary disease, affecting other organ systems (2).

The incubation period for blastomycosis is 3–15 weeks. About 30%–50% of infections are asymptomatic. Pulmonary symptoms are the most common clinical manifestations; however, extrapulmonary disease can frequently manifest as cutaneous and skeletal disease and, less frequently, as genitourinary or central nervous system disease. Liver, spleen, pericardium, thyroid, gastrointestinal tract, or adrenal glands may also be involved (3). Misdiagnoses and delayed diagnoses are common because the signs and symptoms resemble those of other diseases, such as bacterial pneumonia, influenza, tuberculosis, other fungal infections, and some malignancies (4). Accurate diagnosis relies on a high index of suspicion with confirmation by using histologic examination, culture, antigen detection assays, or PCR tests (5).

Antifungal agents, such as itraconazole for mild or moderate disease and amphotericin B for severe disease, can provide effective therapy, especially when administered early (1,2). With appropriate treatment, blastomycosis can be successfully treated without relapse; however, case-fatality rates of 4%–22% have been observed (4,6–9). Although spontaneous recovery can occur (10,11), case-patients often require monitoring of clinical progress and administration of drugs on an inpatient basis. Previous studies estimated average hospitalization costs for adults to be $20,000; that is likely less than the current true cost (12). Some reviews of outbreaks indicate a higher distribution of infection among persons of older age, male sex (2,13), black, Asian, and Native American racial/ethnic groups (3,13), and those who have outdoor occupations (13,14). Both immunocompetent and immunocompromised hosts may experience disease and death (2,6,15–19), although B. dermatitidis disproportionately affects immunocompromised patients, who tend to have more rapid and extensive pulmonary involvement, extrapulmonary infection, complications, and higher mortality rates (25%–54%) (2,6,16–19).

Past studies have expanded the knowledge about blastomycosis through focusing on cases documented in specific immunocompromised persons and statewide occurrences or in areas in which the disease is endemic (4,6–9,16–18); however, such studies may be limited for making definitive conclusions by their scope and small sample size. Much remains unknown about the public health burden of blastomycosis-related deaths in the United States. Reports suggest an increase in the number of blastomycosis cases in recent years (13,20). Clearer identification of risk factors from national data may raise awareness of blastomycosis in the United States and support adding it to the list of reportable diseases in regions where the pathogen is endemic to improve surveillance and control. In this study, we assessed the public health burden of blastomycosis-related deaths by examining US mortality-associated data and evaluating demographic, temporal, and geographic associations as potential risk factors.

Acknowledgments

We thank Matthew Redelings for his contributions to the analysis of data in this study.

Ms Khuu is a doctoral student in epidemiology at the University of California, Los Angeles, School of Public Health. Her research interests include the epidemiology and control of infectious diseases.

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Figure

• Figure. Number of blastomycosis-related deaths and age-adjusted mortality rates per 1 million person-years, by year, United States, 1990–2010.

Tables

• Table 1. Blastomycosis-related deaths by sex, race/ethnicity, age group, and geographic region with corresponding age-adjusted mortality rates, United States, 1990–2010
• Table 2. Age-adjusted time trends in blastomycosis-related mortality rate for sex, race/ethnicity, and geographic region, United States, 1990–2010
• Table 3. Demographic distribution and age-adjusted mortality rates for the Midwestern and Southern regions in the United States, 1990–2010

Suggested citation for this article: Khuu D, Shafir S, Bristow B, Sorvillo F. Blastomycosis mortality rates, United States, 1990–2010. Emerg Infect Dis. 2014 Nov [date cited]. http://dx.doi.org/10.3201/eid2011.131175

DOI: 10.3201/eid2011.131175