Age structure

Age-structured epidemic models divide the population into age groups because contact behaviour, susceptibility and disease outcomes can vary substantially with age.

Age-specific compartments

Instead of one susceptible and infectious population, the model uses variables such as \(S_i(t)\) and \(I_i(t)\) for age group \(i\).

Force of infection

A typical age-specific force of infection has the form

where \(c_{ij}\) represents contact from individuals in group \(i\) with group \(j\).

Why it matters

Age structure can change transmission patterns, intervention effects and predictions of severe disease burden.