The model developed here is quite simple. In particular, it does not account for a potential difference in individuals' infectivity between the acute and chronic phase of the infection. Such levels of complexity could be added to the method. This would make the model more realistic but also more complex, which was not our purpose here. The most important conclusion of the paper, i.e. that dynamic models predict much more variability than models where individuals are independent and hence are sufficient to explain highly variable prevalence data, would remain true for more complex model. Another model assumption is that we neglected the contacts with populations outside the study area (white rectangles in Fig. 1 ). Since we did not find an important effect of the number of infected neighbors on the disease prevalence in populations, we are confident that adding the neglected populations would not deeply affect our results.