Modeling the impact of screening algorithms and prisoner turnover levels on TB transmission in South African prisons

Abstract

Controlling transmission of Mycobacterium tuberculosis (TB) within prisons is a key component of the overall effort against TB in South Africa. In this study, a Monte Carlo discrete event simulation model was used to compare instances of TB transmission occurring in a hypothetical prison cell under different conditions of prisoner turnover, cell ventilation and TB screening. High prisoner turnover rates substantially increased TB transmission. Furthermore, when assuming baseline conditions of no TB screening and poor cell ventilation (1 air change per hour), improved screening with chest radiography and Xpert testing yielded equal or better results compared to improved ventilation (12 air changes per hour) at every level of turnover modeled. This study suggests that the number of prisoners in high-turnover environments should be reduced in order to decrease TB transmission. Directions for future studies include simulating different combinations of TB screening and improved cell ventilation to determine their efficacy in preventing transmission, as well as analysis of the financial and logistical feasibility of implementing these measures.