The development of an infectious disease can be described by simple mathematical models; the course will demonstrate how to construct a spreadsheet implementation, but it's not essential for following the course. Powerful conclusions can be drawn by exploring the effect of changing the "R number". For example, the UK government's response to the Covid-19 had the goal of managing the number of patients requiring intensive care: 'flattening the curve'. The course will also discuss wider situations such as endemic diseases, examining the impact of vaccination and the concept of 'herd immunity'. Note that the emphasis of the course will be on the modelling of outbreaks rather than on the biology of the infectious organism and the search for a vaccine, etc. This course will be essentially the same as last year, but updated to see what can be learnt from later waves.