Fig. 6

Influence of disability onset probabilities \(\theta _f\) and \(\theta _m\) on final disease outcomes. Subfigures show the long-term values of (a) female carriers \(C_f\), (b) male carriers \(C_m\), and (c) the recovered population R(t). As \(\theta _f\) and \(\theta _m\) increase, both \(C_f\) and \(C_m\) decrease due to earlier disability onset, while R(t) exhibits modest nonlinear variation.