They are highly unlikely to become active. Histoplasmosis is an infection caused by a fungus called Histoplasma. The fungus lives in the environment, particularly in soil that contains large amounts of bird or bat droppings. In the United States, Histoplasma mainly lives in the central and eastern states, especially areas around the Ohio and Mississippi River valleys.
Most of infected patients have no symptoms. During a chest X-ray or CT scan, multiple nodules or lesions that are caused by histoplasmosis can be identified. In general, the lesion would be dormant because it has been calcified.