In August 2012, a physician notified the Minnesota Department of Health of two cases of histoplasmosis. Both individuals were carpenters who had worked on an old barn restoration project in Carver County that involved cleaning out the bar, restoring the integrity of the foundation, and replacing deteriorated wood in the floors and walls. During the initial cleaning of the barn, birds, bats, and their droppings, and old hay were removed from the barn. The project began around July 19 and continued until approximately August 9, when work was suspended due to several workers falling ill.

Eighteen of 22 persons associated with the restoration project or property were interviewed. Six of 18 interviewed persons met the case definition. All were employees. The incubation period was 10 days for the two cases for whom a single specific exposure date was known. All six cases sought medical attention. Two cases were diagnosed with histoplasmosis based on a positive urine and serum antigen detection test. Participating in the repair of the foundation was significantly associated with illness (6 of 6 cases vs. 2 of 9 controls; odds ratio, undefined; p=0.007).

Histoplasma can be found in soil and other material that is contaminated with bird and/or bat droppings. The disease is transmitted by inhalation of contaminated dust. It is likely that employees inhaled spores of Histoplasma capsulatum present in the environment while working on the restoration project.