Unraveling the multifaceted impact of tuberculosis on coinfections

Tuberculosis (TB) remains the leading cause of death worldwide from a single bacterial agent. However, an estimated one-quarter of the world's population carries an asymptomatic form of TB. In this state, the host maintains a chronic inflammatory lung environment in which the infection is contained and may even be cleared. TB can be lifelong; thus, patients are likely to contract superinfection by another pathogen. It is therefore relevant to investigate the impact of Mycobacterium tuberculosis (Mtb), the bacterium responsible for TB, on the host's capacity to cope with a second infectious agent. TB is increasingly recognized as a dynamic disease that exists along a broad clinical and immunological spectrum, far beyond the conventional dichotomy of active and latent infection. Yet, in the context of coinfections, this complexity is often overlooked. This review therefore bridges historical outbreaks, global epidemiology, and experimental models to illustrate the interplay between TB and co-occurring infections. In particular, Mtb infection shapes the outcome of secondary infections, while coinfecting pathogens can in turn reshape TB progression, immune control, and disease severity.