A well-documented outbreak in Indiana in the late 1970s affected more than 100,000 people. Except for the Rio Grande Valley, Histoplasma is comparatively less abundant in the Southwest. Here in Arizona, Histoplasma is apparently less common, and its distribution seems to be patchy. Still, detection by sampling and culture of cave soil is difficult. Some Arizona bats create guano deposits in the smallest caves and rock shelters.
Caution is always appropriate.
The disease is not communicable from person to person. No vaccine is commercially available, though several have been investigated. Prevention centers on avoiding inhalation of spores. Many cavers who contract histoplasmosis report having inhaled large doses of cave dust. I came down with it after digging in loose guano deposits in Jamaican caves.