Hopf Bifurcation Analysis of a New SEIRS Epidemic Model with Nonlinear Incidence Rate and Nonpermanent Immunity

Figure 3

Stability features regarding the critical (green) and the zero (black and red) regions. Green denotes the negative slope of the real part of the complex eigenvalues versus , around , red indicates the existence of unstable endemic equilibria for , and black outlines the pairs for which no endemic equilibria arise in the whole range for . The parameters are defined as , , , and and (a) and (b) .

(a)

(b)