Adams-Bashforth 1 Adams–Bashforth technique 1 Adam–bashforth technique 1 COVID-19 1 COVID-19 variant 1 COVID-19 variants 1 Caputo–Fabrizio Caputo–fabrizio 1 Cell proliferation 1 Equilibrium solutions 1 Existence and uniqueness 1 Fixed point arithmetic 1 Fixed point theory 1 Fractional-order models 1 Iterative methods 1 Model solution 1 Numerical scheme 1