ABSTRACT
This chapter focuses on Mycobacterium tuberculosis (Mtb) transmission and its control, with emphasis on the importance of transmission from persons with unsuspected tuberculosis (TB), or unsuspected drug resistance, on effective therapy. Globally, in high burden settings, recent transmission, including reinfection , accounts for most incident TB clinical cases, compared to reactivation of remote latent infection. TB pathogenesis begins through person-to-person transmission, almost exclusively by the airborne route, a relatively unusual transmission route among human pathogens, shared primarily with some respiratory viruses. A convenient way to discuss the determinants of transmission and potential interventions is through the Wells-Riley equation, an idealized steady-state model that has been widely used to better understand the theoretical relationship among factors. Humans vary greatly in resistance to Mtb infection, reinfection, and disease progression, based on both inherited innate immunity, epigenetic modification, and adaptive immunity, further complicated by age, medication, and risk factors such as smoking, air pollution, diabetes and HIV co-infection.
