In realistic epidemic models, a key issue to consider is the representation of the contact process through which a disease is spread, and network models have arisen as good candidates [5] . This has led to the development of "network epidemic models". Network is a flexible concept that can be used to describe, for example, a collection of individuals linked by sexual partnerships [6] , a collection of families linked by sharing workplaces/schools [7] , a collection of cities linked by air routes [8] . Any of these scales may be relevant to the study and control of disease spread [9] .