Histoplasmosis is a fungal infection that is caused by inhaling fungal spores into your lungs. The spores of a fungus are often found in the fecal matter of birds and bats which is often found in soil. People are most commonly exposed to histoplasmosis when these fungal spores are airborne during cleanup or demolition projects. It is most often found in the mid-Atlantic, southeastern, and central regions of the United States. The illness can either be mild or life-threatening. Histoplasmosis most often affects your lungs. However, if the infection is severe, it can spread throughout the entire body. There are about 250,000 people in the United States who get histoplasmosis each year.