90-95% of the population of the ohio river valley has been exposed to histoplasma capsulatum, but relatively few individuals are diagnosed with histoplasmosis. why is this so?

Histoplasmosis is an infection caused by the fungal species known as Histoplasma. It thrives in soil that contains high levels of bird or bad droppings. Even though over 90 percent of the Ohio Valley has tested positive for exposure only persons with weaker immune systems and certain jobs or situations seem to get infected. High risk jobs include agriculture, roofing, construction or being in an environment with bird droppings. 

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