The CBIC Certified Infection Control Exam Study Guide (6th edition) emphasizes that Aspergillus infections associated with healthcare settings are most commonly environmentally acquired, particularly during construction, renovation, or demolition activities. Aspergillus fumigatus is an airborne mold, and transmission occurs through inhalation of spores, not via person-to-person contact.

In this scenario, the infection preventionist should focus on air handling systems and environmental controls, which makes options A, B, and D critical questions. Ensuring that ventilation filters are appropriately maintained (Option A) and evaluating the proximity of air-intake units to construction activities (Option B) are essential elements of an Infection Control Risk Assessment (ICRA). Asking whether Aspergillus was present before construction (Option D) helps determine whether this represents a construction-associated cluster rather than baseline colonization.

Option C is the least relevant because healthcare personnel do not transmit Aspergillus between patients. Unlike organisms spread via contact or droplets, Aspergillus spores are ubiquitous in dust and air and are introduced through environmental disruption. Therefore, evaluating shared staff assignments does not contribute meaningfully to identifying the source of exposure.

For CIC® exam preparation, it is critical to remember that construction-associated aspergillosis investigations focus on air quality, ventilation, and environmental controls—not staff transmission pathways.