The effects of females' susceptibility on the coexistence of multiple pathogen strains of sexually transmitted diseases

We study the dynamics of sexuality. transmitted pathogens in a heterosexually active population where females, are divided into two different groups based on their susceptibility to two distinct pathogenic strains. It is assumed that a host cannot be invaded simultaneously by both disease agents and that when symptoms appear - a function of the pathogen, strain; virulence, and an individual's degree of susceptibility - then individuals are treated and/or recover. Heterogeneity in susceptibility to the acquisition of infection and/or in variability in the length of the infection period of the female subpopulations is incorporated. Pathogens' coexistence is highly unlikely on homogeneously mixing female: and. male populations with no heterogeneity among individuals of either gender. Variability in susceptibility in the female subpopulation makes coexistence. possible albeit under a complex set of circumstances that must include differences in contact/mixing rates between the groups of females and the male population as well as differences in the lengths of their average periods of infectiousness for the three groups.