Fig. 2.

(a) Cumulative frequency distributions for (i) the distances between newly infectious burrow systems and burrow systems known to contain infectious gerbils the previous month (—), and (ii) the distances between occupied burrow systems and burrow systems known to be occupied the previous month (········). (b) An example of the spatial arrangement of empty (○), susceptible () and seropositive (◆) burrow systems at site 1 where data from the winter months of 2002 and 2003 were pooled to classify each burrow system. (c) The cumulative nearest-neighbour distribution function for the set of seropositive burrow systems shown in (b), together with upper and lower envelopes from 99 simulations of complete spatial randomness (points were restricted to be a random subset of the set of occupied burrow systems).