Metodos Matematicos da Fisica

South Korea has a case data with two series: (a) day 1 to 30 , \(1\leq N\leq 30\), fitted curve $Z_{a}$ (green line in Figure 3), and (b) day 31 and after ($N\geq 31$), fitted curve $Z_{b}$ (blue line in Figure 3). These two series are quite different from the Chinese two subseries, where there is a global fitting curve (see Figure 2). As we can see in Figure 3, the thin curve ($Z_{79}$) does not fit properly the whole data. A second wave of Covid-19 cases is in progress in South Korea (curve $Z_{b}$ in Figure 3). Fortunately, this second wave is flattening. The inlet in Figure 3) shows the root mean square (rms) deviations for the last $N$ days from the curve with the full data (upper grey dots) and the curve $Z_{b}$ from the second wave (lower blue dots).

An very important lesson can be learned here: a second wave of infections can come quickly.