BACKGROUND: Histoplasmosis is one of the most common endemic mycoses in the United States. Infection can range from asymptomatic to life-threatening disease. Histoplasmosis is reportable in 10 states and Puerto Rico; however, a standardized case definition was only recently approved by CSTE, and incidence and distribution nationwide remain poorly understood. This study summarizes available state surveillance data to better understand the epidemiologic features of histoplasmosis.
METHODS: Thirteen states provided de-identified data. Contributing states included 10 (Arkansas, Delaware, Illinois, Indiana, Kentucky, Michigan, Minnesota, Nebraska, Pennsylvania, Wisconsin) in which histoplasmosis is currently reportable, 2 (Alabama, Mississippi) in which it was previously reportable, and 1 (Ohio) in which it is not reportable, but data are available. We examined epidemiologic data during 2011–2014 (years for which data were available in all states) and calculated county-specific mean annual incidence rates. Some data elements were only available from certain states. Cases were included if they were classified as a confirmed or probable case by the state.
RESULTS: A total of 3,409 cases were reported; 303 additional cases were detected in Ohio during 2012–2015. County incidence ranged from zero to 39 per 100,000. Mean patient age was 49 years (interquartile range: 33–61), and 2,079 (61%) were male. Of 1,729 patients for which race data was available (from 8 states), most were white (62%) or unknown (26%) race. Common symptoms reported by patients (from 4 states) were cough (74%), shortness of breath (65%), and fever (56%). Thirty percent of 1,154 patients (from 3 states) were immunocompromised, and 57% of 2,218 patients (from 9 states) were hospitalized. Seventy-six (7%) of 1,142 patients died.
CONCLUSIONS: The large proportion of hospitalized patients in this sample suggests that passive surveillance likely fails to capture many cases, particularly less severe illnesses, underestimating the true burden of histoplasmosis. County-level incidence data enhances our understanding of endemic regions in the United States. Expanding reporting to additional states would allow for more comprehensive knowledge of histoplasmosis in the United States.