Bat guano can build up in attics and eaves that have been used by bats, and even if the human occupants of the building are not aware of the dung, they may be harmed by it. After guano has accumulated and been around for a couple of years, a fungus can grow in it, releasing spores into the air that might cause histoplasmosis in humans.

Histoplasmosis can cause serious respiratory disease in humans, causing fever and chest pains. If left untreated histoplsmosis can turn into a chronic lung disease that resembles tuburculosis. In the very young and elderly, or people who already have weakened immune systems, histoplasmosis can be fatal. Histoplasmosis can also travel from the lungs to the eyes causing ocular histoplasmosis syndrome, which destroys the central vision. The lung problems can often times be cured with anti-fungal medications but the ocular disease is not currable.

If bat guano is found in a home or other building it is important to have it removed as soon as possible and by a trained professional. A professional will search for any roosting bats that may be inside, then for any passageways that may be accessible to bats. Any points of entry have to be closed so that the bats do not reappear.

To remove guano, a professional will wear a respirator and dress in protective gear. The guano is usually sprayed with water or a fungicide so that the removal process will not cause the fungus to become airborne. It can then be cleaned up via a specialized vacuum, together with cleaning chemicals, or can be collected manually, or a combination of both.