Dr. Sepkowitz questions our finding of decreased tuberculosis transmission to health care workers because hospital-wide skin-test conversion rates and those among health care workers with direct patient contact did not differ statistically between the preintervention and intervention periods. However, neither of these rates is a sensitive indicator of health care workers' risk for infection; stable hospital-wide rates may be erroneously interpreted as lack of tuberculosis transmission. Job-and ward-specific conversion rates are essential for monitoring tuberculosis transmission to workers in health care settings. After implementation of control measures, conversion rates significantly decreased among health care workers assigned to wards housing patients with tuberculosis. Furthermore, rates among these "high-risk" workers returned to a level similar to that of workers assigned to other wards. These findings strongly suggest that nosocomial tuberculosis transmission to health care workers was not only reduced but was temporally associated with the introduced control measures [1]. Other recently published investigations of nosocomial tuberculosis support our conclusions [2, 3]. Our data show that implementation of measures outlined in the 1990 CDC guidelines can effectively interrupt tuberculosis transmission in health care facilities. Novel measures are not necessary. Proven measures include prompt identification and appropriate isolation and treatment and use of respiratory protective devices by health care workers [4]. Prospective, controlled trials are under way to confirm the efficacy of these control measures.

Dr. Glaser and colleagues also question the potential effect of community tuberculosis control efforts on nosocomial tuberculosis. Although such programs played no role in our study, successful community-based tuberculosis control programs, including directly observed therapy, may favorably affect hospital tuberculosis transmission by reducing the number of patients with tuberculosis.

Mr. Olmsted and colleagues comment on the controversy over measures necessary to prevent occupational acquisition of tuberculosis. The approach of each specialty highlights a different perspective and shows the strengths and weaknesses of each discipline [5]. Infection control personnel want to reduce the risk for infection or disease, whereas occupational health specialists wish to eliminate the possibility of exposure. For most infectious agents, including tuberculosis, exposure to the unknown infectious patient poses the greatest risk to the worker. Therefore, a "zero risk environment" is not possible in health care facilities. The combined expertise of these specialty groups could be used to design studies that would advance our understanding of occupationally acquired infections and would result in appropriate strategies and guidelines for reducing the risk for these infections.