Histoplasmosis

Areas of endemicity for histoplasmosis in the US include the Ohio, Missouri, and Mississippi River valleys. Also endemic in southern Mexico, the Caribbean, and Central and South America. African histoplasmosis is a different clinical entity and is not covered in this topic.

The fungus proliferates well in soil contaminated with bird or bat droppings; therefore, exposure to Histoplasma capsulatum is commonly associated with cave exploration, close proximity to chicken roosts, demolition and excavation, and gathering wood.

Infection is usually asymptomatic or minimally symptomatic; however, infection with a large number of organisms or in people with immunodeficiency can result in severe, symptomatic pulmonary infection, which requires treatment.

Risk factors for more severe respiratory disease include inhalation of a large inoculum, impaired cellular immunity (e.g., AIDS/HIV infection, chronic immunosuppressive therapy), age <2 years, and chronic lung disease.

Histoplasmosis is an infectious disease caused by the fungus Histoplasma capsulatum. It is not communicable from person to person but is acquired from inhalational exposure to infectious spores found in soil contaminated with bird or bat droppings. African histoplasmosis is a different clinical entity and will not be discussed here.