Flow diagram for the TB transmission model.

<p>Susceptible hosts (S) are born at rate with birth rate saturating at high population density, <i>N_m</i>. Hosts in each compartment die at a background mortality rate <i>m_n</i>. Infection of susceptibles occurs at rate <i>b</i> upon contact with TB infectious hosts (I). After TB infection, a fraction <i>f</i> of hosts develop active TB in a short time (fast progression), the remainder enter the latent stage. Latent hosts (L) can activate and develop TB disease sometime later at rate <i>a</i> (slow progression). Latent hosts can also develop active TB after re-infection with TB, with probability of this occurring compared to fast progression of susceptibles reduced by a factor <i>k</i>. Infectious, diseased hosts (I) might regress to the latent stage at rate <i>w</i>. Hosts with active disease die due to diseased induced mortality at rate <i>m_d</i>.