Please look at @glacial‘s link. I have a personal experience with histoplasmosis. After one chest xray, one CT scan, one PET scan and two needle lung biopsies I was diagnosed with histoplasmosis this past July. I went to the doctor for shortness of breath the beginning of June and she ordered the first xray. I spent several weeks during this process worrying that I had lung cancer. My PET scan report showed I had a high probability of malignancy and it had metastasized. It was a very scary time for our family, but I am doing fine now. I just had a follow up xray last week and I will need another Ct scan in January.
I live on a farm and I believe I was exposed to the histoplasma when I was cleaning our garage. We also have many bats and birds in this garage. Most people who get histoplasmosis don’t show any signs and recover from it without any problems. If you or anyone who will be cleaning the barn are vulnerable (young, old or weakened immune system) I would suggest taking precautions and wear a mask when cleaning.