The natural boundaries of a disease which encompass areas with suitable conditions for its transmission are often unknown. This can lead to over-sampling of communities that reside in areas where endemic transmission is either absent or at such low levels that the disease does not represent a public health threat. As a result of this, the data can contain an excess of zero reported cases, a phenomenon known as zero-inflation which has been studied for some tropical diseases; see, for example, Oluwole et al. (2015) for a case-study on soil-transmitted helminths and Amek et al. (2011) and Giardina et al. (2012) on malaria.