Histoplasma capsulatum is a fungus that primarily grows in soil enriched with bird or bat droppings. It is commonly found in certain regions of the United States, particularly in the Ohio and Mississippi River valleys. When the spores of this fungus are inhaled, they can cause a respiratory infection known as histoplasmosis. Most healthy individuals may not experience symptoms, but some can develop flu-like symptoms, including cough, fever, and fatigue. In people with weakened immune systems, histoplasmosis can lead to more severe health issues. Diagnosis typically involves laboratory tests, and treatment may include antifungal medications.