Cough? Check. Fever? Check. But bet you didn't think that this common fungus, Histoplasma capsulatum, could be making you sick. Science Source hide caption itoggle caption Science Source Shots - Health News A Fungus Causes More Unexpected Illnesses In Montana May 14, 2015 The infectious disease world is not short on surprises. Take the people in Montana and Idaho who looked like they had pneumonia. It turned out they had a fungal disease never before seen there.