  In epidemiology, an epidemic is defined as the spread of an infectious
disease to a large number of people in a given population within a short period
of time. In the marketing context, a message is viral when it is broadly sent
and received by the target market through person-to-person transmission. This
specific marketing communication strategy is commonly referred as viral
marketing. Due to this similarity between an epidemic and the viral marketing
process and because the understanding of the critical factors to this
communications strategy effectiveness remain largely unknown, the mathematical
models in epidemiology are presented in this marketing specific field. In this
paper, an epidemiological model SIR (Susceptible- Infected-Recovered) to study
the effects of a viral marketing strategy is presented. It is made a comparison
between the disease parameters and the marketing application, and Matlab
simulations are performed. Finally, some conclusions are carried out and their
marketing implications are exposed: interactions across the parameters suggest
some recommendations to marketers, as the profitability of the investment or
the need to improve the targeting criteria of the communications campaigns.
