  The present article studies the extension of two deterministic models for
describing the novel coronavirus pandemic crisis, the SIR model and the SEIR
model. The models were studied and compared to real data in order to support
the validity of each description and extract important information regarding
the pandemic, such as the basic reproductive number R0, which might provide
useful information concerning the rate of increase of the pandemic predicted by
each model. We next proceed to making predictions and comparing more complex
models derived from the SEIR model with the SIRD model, in order to find the
most suitable one for describing and predicting the pandemic crisis. Aiming to
answer the question if the simple SIRD model is able to make reliable
predictions and deliver suitable information compared to more complex models.
