Tuberculosis elimination and the challenge of latent tuberculosis.

Latent tuberculosis infection (LTBI) affects one third to one fourth of the human population and is the reservoir for a significant proportion of emerging active tuberculosis (TB) cases, especially in low incidence countries. The World Health Organization launched in 2015 the END-TB strategy that aims at TB elimination and promotes, for the first time ever, the management of LTBI. The preventive package, basically consisting of testing and treatment for LTBI in groups at high risk of reactivation, is a mainstay of the first pillar of the strategy, alongside prompt diagnosis and early treatment of both drug-susceptible and drug-resistant TB disease. Testing and treatment for LTBI should be pursued with a programmatic perspective. This implies strong political commitment, adequate funding and an effective monitoring and evaluation system. People living with HIV and children under five years of age who are household contact of a contagious TB cases are primarily targeted in all epidemiological setting. In high resource and low incidence setting, additional at risk populations should also be the target for systematic LTBI testing and treatment. Research is urgently needed to develop diagnostic tests with higher predictive value to identify individuals that progress from infection to disease. Similarly, shorter and safer treatment regimens are needed to make the trade-off between potential benefits and harms more favourable for an increasing proportion of infected individuals.