 
Summary: Chapter 13
TIME DELAYS IN EPIDEMIC MODELS
Modeling and Numerical Considerations
J. Arino
Department of Mathematics,
University of Manitoba, Winnipeg, Manitoba, Canada
arionj@cc.umanitoba.ca
P. van den Driessche
Department of Mathematics and Statistics
University of Victoria BC, Canada
pvdd@math.uvic.ca
1. Introduction
Continuous time deterministic epidemic models are traditionally for
mulated as systems of ordinary differential equations for the numbers
of individuals in various disease states, with the sojourn time in a state
being exponentially distributed. Time delays are introduced to model
constant sojourn times in a state, for example, the infective or immune
state. Models then become delaydifferential and/or integral equations.
For a review of some epidemic models with delay see van den Driess
che [228]. More generally, an arbitrarily distributed sojourn time in a
