The attack rate (proportion of groups becoming infected following a single disease introduction) generally increases with the hotspot radius of attraction R, and the traveler-resident transmission probability P T (Fig. 2 ). This occurs whether or not infected groups are assumed to travel during infection ( Fig. 2 and Fig. S1 in supplemental materials). As predicted by percolation theory [26] , the attack rate also increases with both the withingroup transmission parameter P W and the between-group transmission parameter P B . Interestingly, the highest impact of the hotspot radius of attraction on the attack rate was observed for intermediate values of P W and P B . For low values of P W and P B , inter-group disease transmission primarily occurred between travelling and resident groups and was often not sufficient to sustain an epidemic. For high values of P W and P B , the disease always percolated, even in the absence of the hotspot. For intermediate values of P W and P B , groups infected en route to the hotspot then stochastically triggered small outbreaks around their territories. The epidemiological impact of the hotspot was amplified by this interaction between traveler-resident transmission and neighbour-neighbour transmission.