My A level maths was some time ago admittedly.Mathematics not your strong point either then. Im trying to explain to him why his assumption that a sudden rise in cases is not because the R number has to be greater than 1(which he seems to believe). It only has to be above zero, and depends on the number already positive.
By definition, for more than one person to be infected by 1 person, R must be greater than 1.
For numbers to increase, more than one person must be infected by one person. Ergo, R >1.
How would you attribute the increase?