In July 2011, NIOSH received an HHE request from management representatives at a medical center in Arizona. The request concerned the exposure of employees to Mycobacterium tuberculosis (TB). The management representatives asked for our assistance in evaluating the infection control and occupational health practices related to TB. During an on-site evaluation in August 2011, we reviewed the medical center's TB-related occupational health and infection control policies and practices. We also assessed the ventilation in the airborne infection isolation (AII) rooms and sputum booth, interviewed 39 employees, reviewed pertinent medical records, and observed the respirator fit testing of two employees. We analyzed the medical center's TB screening data and interview data to identify factors associated with having a new positive tuberculin skin test (TST). A health hazard from exposure to Mycobacterium tuberculosis existed at this medical center. Our investigation revealed 18 (2.3%) employees with a TST conversion in 2011

one of these employees was diagnosed with active TB. Most employees who had TST conversions worked in the hospital during the stay of an active TB patient who was not initially placed in AII. This finding suggests that hospital transmission likely occurred. Certified nursing assistants were significantly more likely to have a TST conversion than other hospital employees. Although the medical center's written tuberculosis control program policy was comprehensive, our investigation revealed gaps in implementation of its administrative, engineering, and personal protective equipment (PPE) controls. We found deficiencies in employee TB-related training and screening. Six AII rooms were under positive pressure, and another AII room had fewer than the recommended 6 air changes per hour (ACH) during our visit. Additionally, seven anterooms adjacent to AII rooms had fewer than 10 ACH. We recommended giving TB training to all employees on hire and annually thereafter and considering ways to enforce the requirement for employee TB screening. We recommended that suspect TB patients be promptly placed in an AII room with appropriate signage indicating their status. We also recommended that the seven malfunctioning AII rooms not be used for that purpose. The heating, ventilating, and air-conditioning (HVAC) systems should be rebalanced to ensure that all AII rooms are under negative pressure relative to adjacent anterooms and/or hallways, and doors between anterooms and adjacent hallways should be closed when active TB patients are housed. Negative pressure of airflow should be tested daily in AII rooms used for patients in isolation. We also recommended improvements in respiratory protection training and in respirator fit-testing procedures.