  In this paper, we study the effectiveness of the modelling approach on the
pandemic due to the spreading of the novel COVID-19 disease and develop a
susceptible-infected-removed (SIR) model that provides a theoretical framework
to investigate its spread within a community. Here, the model is based upon the
well-known susceptible-infected-removed (SIR) model with the difference that a
total population is not defined or kept constant per se and the number of
susceptible individuals does not decline monotonically. To the contrary, as we
show herein, it can be increased in surge periods! In particular, we
investigate the time evolution of different populations and monitor diverse
significant parameters for the spread of the disease in various communities,
represented by countries and the state of Texas in the USA. The SIR model can
provide us with insights and predictions of the spread of the virus in
communities that the recorded data alone cannot. Our work shows the importance
of modelling the spread of COVID-19 by the SIR model that we propose here, as
it can help to assess the impact of the disease by offering valuable
predictions. Our analysis takes into account data from January to June, 2020,
the period that contains the data before and during the implementation of
strict and control measures. We propose predictions on various parameters
related to the spread of COVID-19 and on the number of susceptible, infected
and removed populations until September 2020. By comparing the recorded data
with the data from our modelling approaches, we deduce that the spread of
COVID-19 can be under control in all communities considered, if proper
restrictions and strong policies are implemented to control the infection rates
early from the spread of the disease.
