The cat populations observed in this study are of small size, and certainly are not large enough to retain the virus over long periods of time. Since we detected infected cats in 14 out of the 15 populations (and infected males in 13 of them), we can assume regular viral exchange between populations. Previous theoretical studies have shown the importance of the spatial dispersal of the FIV virus between populations [38] . Due to the topographic isolation of our study area, it seems reasonable to assert that viral exchange between the studied populations is primarily responsible for the reintroduction of the virus into populations where it has become extinct. We proposed two different virus dispersal networks between the populations, but neither significantly improved the goodness-of-fit to the observed data. Although our observations are most likely insufficient to capture the exact dispersal network between populations, the networks we analyzed should be quite realistic, because they are consistent with the natural barriers in the study area.