  We discuss the generation of various reproduction ratios or numbers that are
very useful to monitor an ongoing epidemic like Covid-19 and examine the
effects of intervention measures. A detailed SEIR algorithm is described for
their computation, with applications given to the current Covid-19 outbreaks in
a number of countries (Argentina, Brazil, France, Italy, Mexico, Spain, UK and
USA). The corresponding matlab script, complete and ready to use, is provided
for free downloading.
