Figure 2

The dynamic evolution of system (21) when \(\nu =0.5\), with the approximate solution by fractional Chebyshev polynomials \((\varphi _{2},\psi _{2})= (\frac{2(t+2t^{2})}{\pi }, \frac{2(t+2t^{2})}{\pi })\) for Russia in March and April, respectively. In March the number of infections was per person, while in April it was per K (thousand). The connection coefficient in March is \(C_{0.5,2} =0. 79\), while in April it is \(C_{0.5,2} =0. 099\)