We discuss the generation of various reproduction ratios or numbers to monitor the outbreak of Covid-19 or other epidemics and examine the effects of intervention/relaxation measures. A detailed SEIR algorithm is described for their computation, with applications given to the current Covid-19 outbreak in several countries in America (Argentina, Brazil, Mexico, US) and Europe (France, Italy, Spain and UK). The corresponding matlab script, complete and ready to use, is provided for free downloading.