Mathematical Biosciences and Engineering (MBE)

 Modeling diseases with latency and relapse Pages: 205 - 219, Volume 4, Issue 2, April 2007 P. van den Driessche - Department of Mathematics and Statistics, University of Victoria, Victoria B.C., Canada V8W 3P4, Canada (email) Lin Wang - Department of Mathematics and Statistics, University of Victoria, Victoria, BC, Canada, V8W 3P4, Canada (email) Xingfu Zou - Department of Applied Mathematics, University of Western Ontario, London, Ontario N6A 5B7, Canada (email) Abstract: A general mathematical model for a disease with an exposed (latent) period and relapse is proposed. Such a model is appropriate for tuberculosis, including bovine tuberculosis in cattle and wildlife, and for herpes. For this model with a general probability of remaining in the exposed class, the basic reproduction number $\R_0$ is identified and its threshold property is discussed. In particular, the disease-free equilibrium is proved to be globally asymptotically stable if $\R_0<1$. If the probability of remaining in the exposed class is assumed to be negatively exponentially distributed, then $\R_0=1$ is a sharp threshold between disease extinction and endemic disease. A delay differential equation system is obtained if the probability function is assumed to be a step-function. For this system, the endemic equilibrium is locally asymptotically stable if $\R_0>1$, and the disease is shown to be uniformly persistent with the infective population size either approaching or oscillating about the endemic level. Numerical simulations (for parameters appropriate for bovine tuberculosis in cattle) with $\mathcal{R}_0>1$ indicate that solutions tend to this endemic state. Keywords:  bovine tuberculosis, delay differential equation, disease-free equilibrium, endemic equilibrium, global asymptotic stability, tuberculosis, uniform persistence. Mathematics Subject Classification:   92D30, 34D23, 34K20. Received: June 2006;      Accepted: November 2006;      Published: February 2007. 2012 Impact Factor1.195 Journal home Editorial board Readers Email alert Bookmark this page Recommend to friend RSS this journal   Authors Submit an article Track your article Guide for authors Tex file preparation Open access Editors Instruction Login Referees Instruction Librarians Order information Abstracted in