Fakteh Ghanbarnejad (SRH University of Applied Sciences) is visiting us this month, and will give a talk in the usual AM seminar slot on Wednesday 8th October at 1pm in Carslaw 275. We will go to lunch beforehand. All are welcome to both, students get a free lunch. Title: When contagions collide: mathematics of interacting epidemics and beyond Abstract: Most mathematical models of contagion--whether for diseases, computer viruses, or ideas--focus on a single agent spreading in isolation. Reality is far more complex: pathogens interact within hosts, behaviors shape disease transmission, and multiple contagions often overlap in space and time. These interacting contagions can amplify, suppress, or fundamentally alter each other's dynamics. In this talk, I will introduce the idea of contagions as a unifying concept across biology and society, with examples from disease ecology and the One Health perspective, where human, animal, and environmental health are deeply interconnected. I will outline the first mathematical steps in modeling these interactions, beginning with extensions of classical epidemic models and network-based frameworks. Even simple models reveal surprising phenomena: shifts in epidemic thresholds, changes in persistence or/and the order of phase transitions, and unexpected outcomes when contagions couple together.