Tuberculosis (TB) continues to present a major global public health challenge. In 2014, 9.6 million people developed the disease and 1.5 million died. An estimated two billion of the world population is latently infected, and over their lifetime, five to ten percent will progress to active disease.
The bulk of TB morbidity and mortality is concentrated in low and middle income countries. Nevertheless, aided by population movement and migration, TB also presents a challenge in high income countries. The United States (U.S.) is a low-incidence country where immigration has had a substantial impact on TB epidemiology. Public health efforts such as contact tracing and prophylactic treatment of latent infection have led to a substantial decrease in TB incidence over the past 20 years; from 10.4 per 100,000 in 1992 to 3.0 per 100,000 in 2014. This steady decline, however, obscures the substantial burden among foreign-born persons whom continue to account for a larger proportion of the incident cases in the U.S. As incidence is decreasing overall in the general U.S. population, TB is increasingly concentrated within high-risk U.S.-born individual, and immigrant subgroups in large urban centers. In such settings prompt identifications of local transmission is important to the continued efforts towards TB elimination.