What are the initial conditions?
There is no clean answer to this. Infections can be endemic i.e. persist peculiar to a district or particular locality, To study this type of infection you would need to have different environments: e.g. the bottom half of the grid have lower infection rate than the upper half. epidemic i.e. spreading from an initial source to cover the whole region, and perhaps then dying out . To study this you use one initially infected site, and plot the number of infections against time. Assuming the infection ultimately dies out (e.g. if there is no recovery rate) then an epidemic is one where the number of infections is proportional to the size of the system. The final state of an epidemic has no remaining infected sites. pandemic i.e. covers the whole region Here the system has a steady state with a finite number of infections. To study this it doesn’t matter what starting conditions you use (except for a few extreme special cases, like all reisisant or none infected), the system will reach the
