Histoplasmosis is a fungal infection caused by inhaling spores of the Histoplasma capsulatum fungus. It is sometimes referred to as "cave disease," "Ohio valley disease," or "spelunker's lung" due to its association with caves and other enclosed spaces. Other synonyms for histoplasmosis include "darling's disease," "reticuloendothelial cytomycosis," and "Mississippi valley disease." The disease can affect both humans and animals and can range from mild flu-like symptoms to severe pneumonia. It is commonly found in soil contaminated with bird or bat droppings and is prevalent in regions such as the Mississippi and Ohio River valleys, Central and South America, and some parts of Africa. Early diagnosis and treatment are essential for a good prognosis.