Schematic representation of the model.

The square boxes represent classification of the general population into six mutually exclusive subpopulations, i.e., susceptibles S(t), early latents L1(t), late latents L2(t), individuals treated with isoniazid preventive therapy P(t), individuals with active TB I(t), and recovered individuals R(t). All arrows indicate either inflow or outflow or transition between compartments. Blue arrows illustrate transition of latently infected individuals as a result of treatment with IPT. Red dashed arrows show reinfection of late latently infected individuals, individuals treated with IPT and recovered individuals, respectively represented by σi, i = 1, 2, 3.