From a paper I'm currently reading:
In the simplest setting, the average waiting time (or equivalently the departure rate) in each stage is assumed to be equal: the overall infectious period is then described by the sum of n independent exponential distributions, i.e. infectious periods are gamma distributed with a shape parameter n.
Essentially the idea is by having a waiting time go through n exponentially distributed steps, one can arrive at an overall waiting time that's gamma distributed with a shape parameter n.
That I understand - my question is, what's the scale parameter for that gamma distribution?