Figure 2

Basic policies. (a) Under a policy \(P(\tau ,k,d)\), the country locks down to \(k<k_0\) daily contacts whenever the number C(t) of critical cases exceeds a trigger threshold \(\tau\). It reopens (to \(k_0\) daily contacts) once the number of critical cases stays below \(\tau\) for \(d\) consecutive days. (b) We consider four different policies given by a combination of a trigger threshold (low trigger \(\tau _{{\text {low}}}=3\), high trigger \(\tau _{{\text {high}}}=12\)) and a lockdown severity (severe \(k_{{\text {low}}}=1.25\), moderate \(k_{{\text {high}}}=6\)), and common patience \(d=10\) days. (c) Representative runs under the four policies (for 800 days). While with the severe high-trigger policy \(P_{SH}\) (top left) all peaks are similar in shape, with the moderate low-trigger policy \(P_{ML}\) (bottom right) all subsequent peaks are much smaller than the first one. With the moderate high-trigger policy \(P_{MH}\) (top right) the capacity is exceeded and with the severe low-trigger policy \(P_{SL}\) (bottom left) the disease is quickly eradicated.