Figure 1. Schematic relationship between mask wearing and non-mask wearing individuals for pandemic (H1N1) 2009.

Note there are three different diagrams represented: k = 1 (ages 0–17), 2 (ages 18–64), and 3 (ages 65+). The arrows connecting the boxed groups represent the movement of individuals from one group to an adjacent one. Susceptible individuals (S^k or $S_M^k$) can either become exposed (E^k or $E_M^k$) or move between the non-mask wearing (S^k) or mask wearing ( $S_M^k$) susceptible groups. Exposed individuals (E^k or $E_M^k$) can either become infectious (I^k or $I_M^k$) or move between the non-mask wearing (E^k) and mask wearing ( $E_M^k$) exposed groups. Infectious individuals (I^k or $I_M^k$) can recover (R^k), die (D^k), be hospitalized (H^k), or move between non-mask wearing (I^k) and mask wearing ( $I_M^k$) infectious groups. Hospitalized individuals can either recover (R^k) or die (D^k).