Contact tracing is commonly used to identify individuals that have been in contact with infectious individuals, to reduce the number of potential onward infections from traced individuals. Contact tracing was successful in the 2003 SARS epidemic (Lipsitch et al. 2003) , but unsuccessful in the 2001 FMD epidemic in the UK (Ferguson et al. 2001; Keeling et al. 2001; Kao 2003) . For simple unstructured populations, contact tracing has been modelled using a combination of branching process analysis complemented by stochastic simulation models (Müller et al. 2000) . However, in more highly structured contact networks, the properties of the network markedly influence the efficacy of contact tracing. For example, contact tracing is more effective on clustered networks than on random networks (Eames & Keeling 2003; Kiss et al. 2005) , and on scale-free networks a higher tracing effort is needed to control an epidemic than on random Poisson networks .