This document discusses the epidemiology of tuberculosis (TB). It defines epidemiology and TB, describes how TB spreads from person to person through airborne droplets. It discusses factors that influence transmission risk and stopping transmission. It also outlines the incubation period, history of TB discoveries, common epidemiological indices used to measure the TB problem, definitions of different TB cases, the natural history of TB including agent and host factors, and the global and national burden of TB, particularly in India which accounts for over 1/5 of global TB incidence.