A fungal
infection, commonly of the lungs, caused by the
fungus Histoplasma capsulatum. This
fungus is commonly found in bird and/or bat droppings in the Ohio and Mississippi Valley region, the Caribbean Islands and in parts of the Northeast US. It is spread by breathing in the spores of the
fungus. The most definitive test for the
fungus has been from fungal stains and
bone marrow cultures. Blood testing has proved to be less reliable. In areas where H. capsulatum is prevalent, 80 percent or more of the population has been exposed to
infection through breathing in airborne spores produced by the
fungus. People with severely damaged immune systems, such as those with
AIDS, are vulnerable to a very serious disease known as progressive
disseminated histoplasmosis. Nationwide, about 5 percent of people with
AIDS have histoplasmosis, but in geographic areas where the
fungus is common, people with
AIDS are at high risk for
disseminated histoplasmosis.