Assessing the impact of Enhanced-Case-Finding on tuberculosis incidence and transmission in The Gambia using epidemiological and phylodynamic approaches

Background Most tuberculosis (TB) cases in The Gambia are notified in the Greater Banjul Area (GBA). We conducted an Enhanced-Case-Finding (ECF) intervention in the GBA and determined its effect on TB incidence and ongoing TB transmission. Methods This was a cluster randomized trial in which randomly assigned intervention areas of grouped settlements received three rounds of an ECF strategy consisting of sensitization followed by auramine microscopy, whereas TB patients in control areas continued to be identified through passive case finding. The primary outcome was TB incidence rate. To exclude that an increase in notified cases, followed by a decrease in notified cases, would hide the future impact of the intervention, we tested for changes in transmission dynamics using both genetic clustering and phylodynamic methods. Results No significant difference in TB incidence rates, transmission clustering or effective reproductive number was detected between intervention and control areas. Conclusion Although we did not find evidence for decreased TB incidence nor TB transmission through the ECF strategy used, this approach is an examplar of how both classical epidemiology and genomic phylodynamics approaches can be integrated to better assess public health intervention outcomes.