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Histoplasmosis is caused by a fungus, Histoplasma capsulatum, which lives in the environment and grows in association with large amounts of bat or bird droppings. Inhaling its spores can cause an infection in the lungs. However many people that do inhale its spores do not get sick.

Key facts about histoplasmosis

  1. The histoplasmosis fungus, native and common in the Mississippi and Ohio River valleys but rare in Florida, grows in association with large amounts of bat droppings.
  2. Spores are airborne when soil is disturbed, and people then breathe in the airborne spores. If dirt or guano is left undisturbed, fungal spores are not airborne and lung infections in people do not occur.
  3. Histoplasmosis is not transmitted people to people, or animals to people.
  4. Most cases of histoplasmosis in humans resolve within a month without any treatment.
  5. Risk of exposure to histoplasmosis increases with these activities:  creating dust when working with surface soil, cleaning, remodeling, or demolishing old buildings, and exploring caves.
  6. When an accumulation of bat guano is discovered in a building, removing the material is not always best. Simply leaving the material alone if it is in a location where no human activity is likely may be the best course of action.
  7. If guano has accumulated in a building with a dirt floor, it should be removed to prevent growth of histoplasmosis. Caution should be used when removing this guano and a respirator should be worn when guano is disturbed.