With this aim we developed a model in which each site in the two dimensional integer lattice can be in state 0 = healthy, 1,2 = infected by that strain, 3 = infected by both. In words, new 1 infections occur at rate b1 times the fraction of infected neighbors (for your favorite neighborhood) but (a) doubly infected neighbors count for c1 < 1, and (b) infections into a 2 infected site occur at c1 times the rate for an uninfected site. As in the contact process, a plant that is 1 infected becomes healthy at rate d1, but here, doubly infected plants lose their 1 infection at rate d1/c1. There are of course, constants b2, c2, d2 and analogous transitions for 2 infections. Our basic question is: Can the two strains coexist? The picture below of the nearest neighbor system with b1=2, d1=1, b2=3, d2=1, c1 = c2 = shows that the answer is yes.
