Section: New Results
Differential Susceptibility and Infectivity
We have introduced a general epidemic model with different susceptible compartments and different infective compartments. This model addresses the problem of differential susceptibility as well as of differential infectivity. It also takes into account the different flows between different compartments. This model encompasses and generalizes previous models of the literature. The rationale to introduce differential infectivity and susceptibility is motivated by the heterogeneity, concerning the mode of infection, for the individuals. For many reasons difference in susceptibility to infection can occur : genetic variations, different social behaviors, different states of immunization, different vaccines ...The infection by HBV, hepatitis B, is typically a disease where simultaneously differential susceptibility and infectivity appear. We have computed the basic reproduction ratio for this model and have studied the dynamical properties  .