  A pandemic caused by a new coronavirus has spread worldwide, affecting
Argentina. We implement an SEIR model to analyze the disease evolution in
Buenos Aires and neighbouring cities. The model parameters are calibrated using
the number of casualties officially reported. Since infinite solutions honour
the data, we show different cases. In all of them the reproduction ratio $R_0$
decreases after early lockdown, but then raises, probably due to an increase in
contagion in highly populated slums. Therefore it is mandatory to reverse this
growing trend in $R_0$ by applying control strategies to avoid a high number of
infectious and dead individuals. The model provides an effective procedure to
estimate epidemic parameters (fatality rate, transmission probability,
infection and incubation periods) and monitor control measures during the
epidemic evolution.
