Breban et al. [33] showed that two individual-level models having exactly the same expectations of the corresponding population-level variables may yield different R 0 values. They showed that obtaining R 0 from empirical contact-tracing data collected by epidemiologists and using this R 0 as a threshold parameter for a population-level model could produce misleading estimates of the infectiousness of the pathogen, the severity of an outbreak, and the strength of the medical and/or behavioural interventions necessary for control. Thus, measuring R 0 through contact tracing (as generally occurs during an outbreak investigation) may not be a useful measure for determining the strength of the necessary control interventions.