Video S1 Model dynamics. The model shows one simulation run corresponding to the Sick-travel model. White, red and black squares represent susceptible, infected and removed groups, respectively. Blue squares represent groups travelling to the hotspot at each time step. The hotspot, in green, is in the middle of the lattice. The disease is introduced at the periphery. (WMV) The Dispanins: A Novel Gene Family of Ancient Origin That Contains 14 Human Members The Interferon induced transmembrane proteins (IFITM) are a family of transmembrane proteins that is known to inhibit cell invasion of viruses such as HIV-1 and influenza. We show that the IFITM genes are a subfamily in a larger family of transmembrane (TM) proteins that we call Dispanins, which refers to a common 2TM structure. We mined the Dispanins in 36 eukaryotic species, covering all major eukaryotic groups, and investigated their evolutionary history using Bayesian and maximum likelihood approaches to infer a phylogenetic tree. We identified ten human genes that together with the known IFITM genes form the Dispanin family. We show that the Dispanins first emerged in eukaryotes in a common ancestor of choanoflagellates and metazoa, and that the family later expanded in vertebrates where it forms four subfamilies (A–D). Interestingly, we also find that the family is found in several different phyla of bacteria and propose that it was horizontally transferred to eukaryotes from bacteria in the common ancestor of choanoflagellates and metazoa. The bacterial and eukaryotic sequences have a considerably conserved protein structure. In conclusion, we introduce a novel family, the Dispanins, together with a nomenclature based on the evolutionary origin. Membrane proteins are essential for the ability of all cellular organisms to respond and interact with their environment. Therefore they have attained large research interest and are one of the major groups of drug targets [1] . We have previously estimated that 27% of the human genes codes for alpha-helical membrane proteins and provided a comprehensive classification based on their function and evolutionary origin [2] . However, the identification and annotation of many membrane bound protein families is still being revised. We have during recent years worked on the annotation of both G protein-coupled receptors [3, 4] and solute carriers [5] and most of the genes of these large superfamilies now have a clear identity and annotation. There is however still large work to be done to clarify the identity, annotation and the evolutionary history of several families of membrane bound proteins. Establishing a rigid nomenclature based on evolutionary information and structural features of the predicted proteins facilitates prediction of the functional role of these genes that often have only have been studied in large gene or transcription consortia.