Fig. 9.

The unidentifiability surface defined by (5.6). The red plotted points are the parameter values that minimized (landed in the smallest 1% of values of) the loss function $L\left({\beta }^{\prime },z^{\prime },d^{\prime }\right)$ from the nonlinear SEUIR model (5.2), where w′ = w = 0.2 was assumed known. The parameters generating the input I(t) were $(\beta ,z,w,d)=(0.9,0.3,0.2,0.5)$. The input I (t) was used from the prepeak time interval [0, 50]. The surface is colored corresponding to R₀. (Color available online.)