Figure 4.

A one-parameter bifurcation diagram and example time-series for the two-disease age-structured model. In all panels, diseases 1 and 2 are identified by black and grey, respectively. A₁ and A₂ represent, respectively, the mean age at infection for diseases 1 and 2. Disease 1 has the same epidemiological traits as measles (table 1), whereas disease 2 has the same epidemiological traits as whooping cough except that the force of infection is assumed to be λ₂=hλ_wc, where λ_wc is the force of infection for whooping cough (table 1). The seasonal amplitude is fixed at b=0.2.