Evolution of state proportions – S_t (susceptible), I_t (infected, detected or not, ), R_t (recovered and immune, detected or not, ), U_t (hospitalized in ICU), D_t (dead), ℜ_t (dynamic version of the reproduction number), W_t (labor force available), Q_t (susceptible to be quanrantines, ) and δ_t (lockdown intensity) – with optimal control δ (plain line) and without control (dashed line). States vary here from t = 0 (beginning of the pandemic, or at least of possible measures, with δ ≥ 0) to t = 700, and computations are based on a dt = 1∕5 days.