Bacteria and mold are not the only causes of lung infections. Fungus, such as those found in soil and bird droppings, can also cause lung infections. Find out about histoplasmosis and how you can avoid exposure to this infectious fungus. Do you have a question about your lung disease? Have you been searching the internet, and just can't seem to find the answer you've been looking for? Maybe you just need clarification about something your doctor explained to you at your last office visit.