Fig. 6

Effect of control cost for health education: a–d Time series dynamics of infections, e–h The optimal control strategy. The solid and dashed curves represent the scenarios for \({C}_{1}=3\times {10}^{5}\) and \({C}_{1}=3\times {10}^{6}\), respectively. Here \({{C}_{2}=C}_{3}={C}_{4}=3\times {10}^{5}\), the values of other parameters are listed in Table 1, and the initial conditions are same with those in Fig. 5