A social model for the evolution of sexually transmitted diseases

We have introduced recently a model for the spread of sexually transmitted diseases, in which the social behavior is incorporated as a key factor for the further propagation of the infection. The system may be regarded as a society of agents where in principle anyone can sexually interact with any other one in the population. The social behavior is taking into account by means of two parameters: the fraction of singles ρs and the promiscuity p. The promiscuity parameter defines the per individual daily probability of going out to look for a sexual partner, abandoning its eventual mate. In this contribution we show that the interaction between this two parameters give rise to a non-trivial epidemic threshold condition, when going from the homogeneous case (ρs=1) to heterogeneous cases (ρs<1). These results can have profound implication in the interpretation of real epidemic data.