Electronic Journal of Differential Equations,
Vol. 2007(2007), No. 77, pp. 1-17.

Title: Bifurcation analysis on a delayed SIS epidemic model with 
       stage structure

Authors: Li Liu       (South China Normal Univ., Guangzhou, China)
         Xiangao Li   (South China Normal Univ., Guangzhou, China)
	 Kejun Zhuang (South China Normal Univ., Guangzhou, China)

Abstract:
 In this paper, a delayed SIS (Susceptible Infectious Susceptible)
 model with stage structure is investigated. We study the Hopf
 bifurcations and stability of the model. Applying the normal form
 theory and the center manifold argument, we derive the explicit
 formulas determining the properties of the bifurcating periodic
 solutions. The conditions to guarantee the global existence of
 periodic solutions are established. Also some numerical
 simulations for supporting the theoretical are  given.
  
Submitted February 6, 2007. Published May 22, 2007.
Math Subject Classifications: 34K13, 34K18, 34K20.
Key Words: SIS model; delay; Hopf bifurcation; stability;
           periodic solution.