  Different countries -- and sometimes different regions within the same
countries -- have adopted different strategies in trying to contain the ongoing
COVID-19 epidemic; these mix in variable parts social confinement, early
detection and contact tracing. In this paper we discuss the different effects
of these ingredients on the epidemic dynamics; the discussion is conducted with
the help of two simple models, i.e. the classical SIR model and the recently
introduced variant (A-SIR, arXiv:2003.08720) which takes into account the
presence of a large set of asymptomatic infectives.
