Many species from groups as diverse as mammals, birds, fish, insects and other invertebrates undertake regular long-distance movements to track seasonal changes in resources and habitats. The most dramatic migrations can span entire continents or hemispheres, take several months to complete, and are accompanied by high energetic demands and extreme physiological changes. These journeys can have profound consequences for the ecology and evolution of the migratory species, and also for the pathogens and parasites they harbor. Owing to their long-distance movements and exposure to diverse habitats, migratory animals can have far-reaching implications for the emergence and spread of infectious diseases. While previous work on the role of host dispersal in infectious disease dynamics has focused on spatially localized or random dispersal, relatively few studies have examined how regular, long-distance movements that characterize seasonal migration affect the transmission and evolution of pathogens within host populations, and the response of migratory species to infection risks. This proposed organized oral session would allow the synthesis of potential consequences of long-distance migrations for host-pathogen dynamics and consider how human activities can alter disease exposure in migratory populations. The session is particularly timely given that migratory animals are implicated in the transport of emerging zoonotic pathogens of pubic health concern to new geographic areas. These pathogens include but are not limited to West Nile virus, avian influenza, SARS and henipaviruses. At the same time, long- distance movements can alter infection dynamics within migratory species through changes in host immunity, aggregation, mortality and habitat use. In some cases, seasonal migration appears to keep animal populations healthy. For example, greater migratory distances have contributed to lower parasite prevalence of a protozoan parasite of monarch butterflies. Other work suggests that species of conservation concern or economic importance face increased disease burden through anthropogenic activities, for example increased exposure of wild salmon to lice following the establishment of year-round salmon farms. Because migratory species are declining globally and are under increasing threat from human activities, understanding how migration changes infectious disease processes is an area in urgent need of integrative research.