Symmetric movement - effect of IPT coverage for 50 days stay. Model results with symmetric movement and equal population sizes (m =1, p12/p21 = 1, p21 = 0. 02 per day), showing the effect of increasing IPT coverage with SP on the percent increase of R1 relative to RS (Graph (a)) and R2 relative to R1 (Graph (b)) resistance. The parameter p12 is the rate of movement from the high transmission area to the low transmission area, and p21 is the rate from the low transmission area to the high transmission area. , is the ratio of the high transmission population to that of low transmission population.