Perhaps this is only tangentially relevant to what you want, as the people who are most interested in this are not mathematicians but health scientists interested in using certain games as models for the spread of disease. That said, a particularly infamous incident in World of Warcraft has attracted the attention of many serious researchers, some of whom have published papers in scientific journals on the matter (for example, the following two papers: https://www.ncbi.nlm.nih.gov/pubmed/17301707 and http://www.sciencedirect.com/science/article/pii/S1473309907702128).

A Wikipedia summary of the incident can be found here: https://en.wikipedia.org/wiki/Corrupted_Blood_incident

As a young lad I experienced this myself while playing the game.