title: An epidemiological model with a delay and a nonlinear incidence rate.
abstract: An epidemiological model with both a time delay in the removed class and a nonlinear incidence rate is analysed to determine the equilibria and their stability. This model is for diseases where individuals are first susceptible, then infected, then removed with temporary immunity and then susceptible again when they lose their immunity. There are multiple equilibria for some parameter values, and, for certain of these, periodic solutions arise by Hopf bifurcation from the large nontrivial equilibrium state.
authors.affiliation: Department of Mathematics, University of Iowa, Iowa City 52242.
authors.forename: H W
authors.initials: HW
authors.lastname: Hethcote
authors.forename: M A
authors.initials: MA
authors.lastname: Lewis
authors.forename: P
authors.initials: P
authors.lastname: van den Driessche
mesh_terms: D004812:Epidemiologic Methods; D008433:Mathematics; D008954:Models, Biological