Although very common, the homogeneous assumption used in the previous section to derive the constitutive deterministic equations of basic epidemic processes may be inadequate in several real-world situations where individuals
have large heterogeneity in the contact rate, a specific frozen pattern of interaction, or are in contact with only a
small part of the population. These features may have different
relevance depending on the disease or contagion process
considered. However, a wide range of social and biological
contagion processes requires capturing the individuals’
contact pattern structure in the mathematical modeling
approaches. This is even more relevant, because most realworld
systems show very complex connectivity patterns
dominated by large-scale heterogeneities described by
heavy-tailed statistical distributions.