April 28th, 2020.  There is of course at this time a great deal of concern about the impact of the covid-19 pandemic on the world. A simple multi-type SIR epidemic model is explored here:

• Rogers, L.C.G. (2020). Ending the COVID-19 epidemic in the United Kingdom. Preprint (arxiv 2004.12462). Jupyter notebook on Google Colab.