The correct answer is C: interviewing the source, defining the exposure, notifying the discharged patients with true exposure, and reporting to the Office of Public Health.

RATIONALE: Ensure there is a true exposure. This happens by talking to the source patient (and their physician). Once the infection is confirmed you must define an exposure. Most health departments will not do this for you (so, not A). Notification should only go to the patients that meet the exposure definition. Notifying everyone (B) would lead to unnecessary panic.