We identified 1,216 blastomycosis-related deaths among 49,574,649 deaths in the United States during 1990–2010. Among those 1,216 deaths, blastomycosis was reported as the underlying cause of death for 741 (60.9%), and as a contributing cause of death for 475 (39.1%). The overall age-adjusted mortality rate for the period was 0.21 (95% CL 0.20, 0.22) per 1 million person-years. Using Poisson regression, we identified a 2.21% (95% CL −3.11, −1.29) decline in blastomycosis-related mortality rates during the period (Figure).

Our findings indicate that blastomycosis is a noteworthy cause of preventable death in the United States. These findings confirm the demographic risk factors of blastomycosis indicated in previous case reports and extend these to mortality rates. Blastomycosis death occurred more often among older persons than among younger persons (24), and more often among men than women (2,24). The age association found likely represents waning age-related immune function and higher prevalence of immunocompromising conditions. The observed sex differences in blastomycosis mortality may be attributable to differences in occupational or recreational exposures that increase risk for infection (14). For example, those who work outdoors involving construction, excavation, or forestry, or participate in outdoor recreational activities such as hunting (7,11), may more likely be exposed than those who principally work indoors.

The disproportionate burden of blastomycosis deaths sustained by persons of Native American or black race is also consistent with previous reports (3,24). Increased exposure and prevalence of infection, reduced access to health care, and genetic differences may play a role in the observed race-specific disparities in blastomycosis mortality rates (25). A finding of the current study is that even though persons of Asian descent are at lower risk for dying from blastomycosis than whites, those who died from blastomycosis did so at a much younger age (22.6 years younger). This disparity is even greater in the midwestern region, where Asians died at an age 27.2 years younger than did whites.

Consistent with the recognized geographic distribution of B. dermatitidis (1,2), we found that death related to blastomycosis occurred more often among persons who resided in the midwestern or southern regions than among those in the western and northeastern regions. During the study period, the southern region showed decreases in mortality rates, and the midwestern region, which had the highest mortality rate, showed an increase in rate.

The use of population-based data and large numbers can provide insight, though some limitations associated with using MCOD data should be considered. First, potential underdiagnosis and underreporting of death related to blastomycosis may lead to underestimates of mortality rates and the true public health burden of blastomycosis in the United States. Low physician awareness of blastomycosis may be a contributor. Second, it was not possible to verify accuracy of recorded data or access supplemental data. For example, there may be reporting errors regarding correct race/ethnicity identification on death certificates and in population census reports. Third, we could not adjust for other possible confounders (i.e., smoking, socioeconomic factors, activity, lifestyle, occupation) because these data are not recorded on death certificates. These limitations must be considered along with our findings.

This study sheds light on the scope of the incidence of blastomycosis in the United States, though the true incidence may be greater than that reported here. Although B. dermatitidis infection may be difficult to prevent because of its widespread distribution in areas where blastomycosis is endemic, deaths resulting from blastomycosis can be prevented with early recognition and treatment of patients with symptomatic infection. The continued incidence of blastomycosis in the United States, as indicated by the observed modest decrease in the mortality rates over the 21-year study period, calls for improvement in provider and community awareness, which may lead to including blastomycosis as a diagnostic consideration in patients with pulmonary disease refractory to treatment. Our findings, recent reports of disproportionately high infection rates among Asians (26), and the lack of decline in the mortality rates in the midwestern region support further investigation. We also encourage improvements in blastomycosis surveillance that involve examining trends in incident cases, hospitalization (including length of stay), timely diagnosis, and treatment to further elucidate the burden of blastomycosis in the United States.