We consider a model for the spread of an epidemic through a population
divided into m groups, in which infectives move from group to group a
nd infect only within their current group. For both deterministic and
stochastic versions of this model, the effect on the total size of the
epidemic of varying the speed with which infectives move between grou
ps is considered. We also compare the distribution of the total size o
f this model with that of a suitably matched model in which infectives
cannot move between groups, but are able to infect outside their own
group.