When considering both the SIR dynamics and invasion/persistence of the three density-dependent functions, a contrast emerges than can have significant implications for fitting a β-density function to epidemiological data: while there was a clear effect of function shape on invasion and persistence, SIR dynamic patterns were less distinct. This means that it could be difficult to discern between different contact–density functions when fitting model parameters to real, inherently noisy data . Nevertheless, because the functions do introduce different invasion and persistence probabilities, it will, in some situations, be crucial to implement the correct function. Ideally, this choice is based on the quantified contact–density or transmission–density relationship of the host/infection system that is being studied, but such data are rarely available.