Epidemic theory and group violence

Background Epidemics can be represented mathematically using a variety of models. One of these, the Kermack-McKendrick model, has been used to support health policy decisions concerning vaccination requirements. An unrelated body of literature suggests that some behaviours, including some types of violence, may spread in ways analogous to the contagious spread of infectious diseases, a process that has been characterized as “behavioural contagion”. Methods Various parameter values reflecting the characteristics of crowds were substituted into the Kermack-McKendrick model. Computer simulations were used to evaluate the impact of these parameter values. Results The simulations reproduced several features of crowd violence: the tendency for riots to occur in large groups, the importance of rapid removal of violent individuals from crowds,and the roles of alcohol consumption and social identification processes. Conclusions Epidemic models may be of relevance to the prevention and control of violent behaviour as they can assist with the identification of highrisk situations and prevention strategies. Theoretical constructs related to epidemic theory may have broad applicability for modelling the unstable course of some mental disorders.