While TB disease rates are leveling off or declining in most of the world, with one third of humanity infected and 1.8 million deaths a year, it remains a major public health problem. The main threat to global public health from TB is the continually increasing number of infections and increasing resistance to treatment in sub-Saharan Africa. Health care workers are at high risk for TB and their loss to the infections of TB and HIV is adding further strain to an already fragile health system. Research done thus far on the rate HCWs become infected with TB is limited, and the difference in risk among various occupational groups is unclear. Methods of TB control and prevention have been effective in wealthy countries and in the few middle income countries that have implemented them in limited settings. It remains unclear, however, if these methods can protect health care workers in high risk areas. Also unclear is which infection control interventions, if any, carry practical benefits that outweigh their costs in high risk areas. It is too difficult to evaluate these questions with the common test for L TBI (TST) because the TST is a poorly effective test, both non-sensitive and non-specific in the high-risk TB settings of subSaharan Africa. A new test for L TBI is now available, the IGRA. The IGRA has some qualities that may make it a better test for evaluating TB exposure in HCWs. This pilot study proposes to use an IGRA to estimate the annual risk of newly established and transient MTB infections in health care workers employed in a setting with high rates of TB and HIV. We will focus on two different groups of HCWs. First we will follow the risks of conversion as well as reversion and variability of the IGRA as compared to TST in nurses and technicians working in TB clinics. This is an expansion of the study of 10 HCWs done by Joshi et al in India. We will use the data to gain a better understanding of the use of the IGRA in high risk settings. Second we will evaluate baseline risk of conversion in students whose risk profile should parallel the general population at baseline then increase to that of HCWs as they begin working in clinical medicine and have increased patient contact. We aim to use this methodology and baseline information to plan future studies to assess the effectiveness of TB infection control measures in prospective controlled trials within health care settings in subSaharan Africa.Master of Public Healt
