This Demonstration illustrates a very simple multiple epidemic model. At every iteration a random cell is chosen. The cell acquires the value (disease) of one of its four orthogonal neighbors unless it has previously assumed that value at a different time. Then, with a fixed probability, a random cell is chosen and it acquires a new value (disease) not yet found in the array. The model assumes that hosts can only be infected by one disease at a time, that being infected by another disease cures the original one, and that re-infection with the same disease multiple times is impossible.

This Demonstration is based on [1], which includes an analysis and discussion of the model. Boundary conditions are periodic.

Snapshot 1: a single disease spreading in a roughly circular manner

Snapshot 2: competition between two diseases

Snapshot 3: many diseases competing; disease emergence rate set very high

Reference

[1] K. Sneppen, A. Trusina, M. H. Jensen, and S. Bornholdt, "A Minimal Model for Multiple Epidemics and Immunity Spreading," PLoS ONE, 5(10), 2010 p. e13326.