title: A simple SIS epidemic model with a backward bifurcation.
abstract: It is shown that an SIS epidemic model with a non-constant contact rate may have multiple stable equilibria, a backward bifurcation and hysteresis. The consequences for disease control are discussed. The model is based on a Volterra integral equation and allows for a distributed infective period. The analysis includes both local and global stability of equilibria.
authors.affiliation: Department of Mathematics and Statistics, University of Victoria, B.C., Canada. pvdd@math.uvic.ca
authors.forename: P
authors.initials: P
authors.lastname: van den Driessche
authors.forename: J
authors.initials: J
authors.lastname: Watmough
mesh_terms: D003141:Communicable Diseases / Q000453:epidemiology / Q000635:transmission*; D004196:Disease Outbreaks / Q000517:prevention & control / Q000706:statistics & numerical data*; D018562:Disease Transmission, Infectious; D006069:Gonorrhea / Q000453:epidemiology / Q000517:prevention & control / Q000635:transmission; D006801:Humans; D008954:Models, Biological