One of the factors that contribute to the complexity of the dynamics of infectious diseases is that the pathogens constantly go through mutation and other forms of short term evolution. The host population dynamics is one of the major selective forces that strongly influence the course of pathogen evolution. In this study, we examine such an influence by the host population dynamics on the latency of the disease by studying two compartmental models that describe two different host ecologies: one similar to urban centers and one to rural areas. It is shown that the urban host ecology tends to select pathogen strings with a short latency while the rural ecology those of a long latency. These findings suggest that different control strategies should be considered for diferent host ecological environments.