For the joint analysis of two or more diseases, we introduce a generalization of the shared component model (9) where the underlying risk surface for each disease is separated into shared and disease-specific components. We then propose a multivariate extension of the surveillance CPO that incorporates information from the different diseases and, consequently, facilitates the outbreak detection work. The multivariate surveillance technique has the ability to detect outbreaks of disease in either one or in a combination of diseases.