Regulating the risk of tuberculosis transmission among health care workers

The 1994 Centers for Disease Control and Prevention guidelines on preventing tuberculosis (TB) transmission among health care workers (HCWs), and the 1997 Occupational Safety and Health Administration (OSHA) proposed TB standard, do not address the issue of acceptable risk. Further, many infection control personnel oppose OSHA's promulgating a standard because they believe most TB infections among HCWs are nonoccupational in origin. This article examines the relationship between TB infection and disease rates, and introduces a probability framework to apportion infection risk between occupational and nonoccupational exposure. It is argued that most TB infections among HCWs are work-related. A 0.2% overall annual risk of TB infection (accounting for both workplace and community exposure) is proposed as acceptable, because in the context of an infection surveillance program it limits an HCW's cumulative disease risk close to the value for the general United States population. Based on the probability framework, an estimate of the background community infection rate, and the traditional Wells-Riley risk model, it is shown that a target workplace infection risk value can be derived and expressed in terms of an expected pulmonary dose. The latter target dose informs risk management decision-making.