More than half of infectious diseases in humans, from Ebola to Zika, come from animals. But figuring out when those diseases are going to make the species jump has been tough. Now, a team of U.K. scientists has developed a new model to predict when host species and humans will interact, based on climate change, population size, land use, and the known locations of host species, Reuters reports. The model, which pulls together 45 years of Lassa fever outbreak data in West Africa, predicts that the number of people infected by Lassa virus (above)—spread by multimammate rats—will double by 2070, according to the study in Methods of Ecology and Evolution. The researchers think they can use this same type of modeling to predict the outbreak of other diseases, and they hope their findings will assist governments in preparing for and responding to disease outbreaks.