The article "How should pathogen transmission be modelled?" by McCallum, Barlow, and Hone discusses the importance of accurately modeling pathogen transmission in host–pathogen models. The authors highlight that the behavior of these models is significantly influenced by how transmission between infected and susceptible hosts is modeled. Traditionally, the 'mass action' assumption has been used, but recent studies suggest that this model may not always be accurate. Alternative models of transmission are emerging, and empirical tests of transmission dynamics are becoming more common. The key point is that the mode of transmission is crucial for understanding disease control strategies and predicting the impact of pathogens in different populations. The authors recommend using host densities rather than actual numbers to represent host populations, as this can better capture the dynamics of transmission. They also suggest evaluating multiple alternative models and estimating the force of infection, which is a function of both host densities and the distribution of infectious stages. The article reviews several studies that have found the traditional mass action model inadequate for describing pathogen transmission in various contexts, such as cannibalism, predation, and vector transmission. It concludes by emphasizing the need for more spatially explicit models and more relevant experimental and observational data to improve the accuracy of transmission models.The article "How should pathogen transmission be modelled?" by McCallum, Barlow, and Hone discusses the importance of accurately modeling pathogen transmission in host–pathogen models. The authors highlight that the behavior of these models is significantly influenced by how transmission between infected and susceptible hosts is modeled. Traditionally, the 'mass action' assumption has been used, but recent studies suggest that this model may not always be accurate. Alternative models of transmission are emerging, and empirical tests of transmission dynamics are becoming more common. The key point is that the mode of transmission is crucial for understanding disease control strategies and predicting the impact of pathogens in different populations. The authors recommend using host densities rather than actual numbers to represent host populations, as this can better capture the dynamics of transmission. They also suggest evaluating multiple alternative models and estimating the force of infection, which is a function of both host densities and the distribution of infectious stages. The article reviews several studies that have found the traditional mass action model inadequate for describing pathogen transmission in various contexts, such as cannibalism, predation, and vector transmission. It concludes by emphasizing the need for more spatially explicit models and more relevant experimental and observational data to improve the accuracy of transmission models.