  We consider multiple diseases spreading in a static Configuration Model
network. We make standard assumptions that infection transmits from neighbor to
neighbor at a disease-specific rate and infected individuals recover at a
disease-specific rate. Infection by one disease confers immediate and permanent
immunity to infection by any disease. Under these assumptions, we find a
simple, low-dimensional ordinary differential equations model which captures
the global dynamics of the infection. The dynamics depend strongly on initial
conditions. Although we motivate this article with infectious disease, the
model may be adapted to the spread of other infectious agents such as competing
political beliefs, rumors, or adoption of new technologies if these are
influenced by contacts. As an example, we demonstrate how to model an
infectious disease which can be prevented by a behavior change.
