Multistate Epidemiology of Histoplasmosis, United States, 2011–2014 1

Histoplasmosis is one of the most common mycoses endemic to the United States, but it was reportable in only 10 states during 2016, when a national case definition was approved.To better characterize the epidemiologic features of histoplasmosis, we analyzed deidentified surveillance data for 2011-2014 from the following 12 states: Alabama, Arkansas, Delaware, Illinois, Indiana, Kentucky, Michigan, Minnesota, Mississippi, Nebraska, Pennsylvania, and Wisconsin.We examined epidemiologic and laboratory features and calculated state-specific annual and county-specific mean annual incidence rates.A total of 3,409 cases were reported.Median patient age was 49 (interquartile range 33-61) years, 2,079 (61%) patients were male, 1,273 (57%) patients were hospitalized, and 76 (7%) patients died.Incidence rates varied markedly between and within states.The high hospitalization rate suggests that histoplasmosis surveillance underestimates the true number of cases.Improved surveillance standardization and surveillance by additional states would provide more comprehensive knowledge of histoplasmosis in the United States. H istoplasmosis is an infection caused by the soil-dwellingthermally dimorphic fungus Histoplasma capsulatum (1).Infection typically results from inhalation of aerosolized spores.Only 1% of sporadic infections are estimated to be symptomatic, although attack rates during outbreaks have been as high as 50%-100%, possibly from high-dose exposure (2).Most symptomatic infections involve primary pulmonary disease; however, extrapulmonary and severe disseminated disease can occur, especially in immunosuppressed persons.Histoplasmosis is often described as the most common mycosis endemic to North America (1), although data to support this statement are limited, given a lack of national public health surveillance.Although once thought to be endemic to a relatively narrow geographic area, histoplasmosis has been increasingly detected in many parts of the world (3,4).According to histoplasmin skin test surveys performed in the 1950s and 1960s in the United States, areas surrounding the Ohio and Mississippi River Valleys are recognized as the regions of predominant histoplasmosis endemicity (5).However, locally acquired infections have been described outside these areas, suggesting that the geographic range of Histoplasma in the United States is wider than is often appreciated (6).This incomplete knowledge about geographic areas of risk could deter clinicians from considering histoplasmosis as a cause of illness, leading to misdiagnosis and inappropriate treatment.A key data source for information about the current geographic distribution and epidemiology of histoplasmosis is disease surveillance.As of 2016, histoplasmosis was reportable in 10 states but not notifiable nationally.Reportable diseases are those that healthcare providers and laboratories are required to report to state, territorial, or local public health authorities.