A MULTI-GROUP SIR EPIDEMIC MODEL WITH AGE STRUCTURE

This paper provides the first detailed analysis of a multi-group SIR epidemic model with age structure, which is given by a nonlinear system of 3n partial differential equations. The basic reproduction number R-0 is obtained as the spectral radius of the next generation operator, and it is shown that if R-0 1, then the disease-free equilibrium is globally asymptotically stable, while if R-0 > 1, then an endemic equilibrium exists. The global asymptotic stability of the endemic equilibrium is also shown under additional assumptions such that the transmission coefficient is independent from the age of infective individuals and the mortality and removal rates are constant. To our knowledge, this is the first paper which applies the method of Lyapunov functional and graph theory to a multi-dimensional PDE system.