FIG. 1.

Example of a Susceptible–Exposed–Infected–Recovered (SEIR) model of COVID-19 [Eqs. (7)–(10)] with $\lambda =1/S(0)$, $\alpha =0.27$, $\gamma =0.37$. Initial conditions are set to $I(0)=6$, $S(0)=88000$, $E(0)=R(0)=0$. (a) Time evolution for the variables of the system; (b) time evolution for the total number of infections $C(t)$ against the Chinese data with $t=1$ corresponding to December 19, 2019. The inset shows the outcome of the grid search procedure, where the root mean square error between the Chinese data and the modeled $C(t)$ is minimized.