Electronic evaluation of infection risk from room environment and prior room occupants: the transmission from room environment events (TREE) measure.

Over a 2-year period, we identified Transmission from Room Environment Events (TREE) across the Johns Hopkins Health System, where the subsequent room occupant developed the same organism with the same antimicrobial susceptibilities as the patient who had previously occupied that room. Overall, the TREE rate was 50/100,000 inpatient days.