In recent decades the steady increase in global temperature has had a dramatic impact on our oceans, resulting in habitat loss and changes in species distribution for both predator and prey. Ecological changes impact host susceptibility to disease on several levels including immunological health and pathogen exposure. Environmental changes directly impact pathogen fitness, with temperature, salinity, and pH as important parameters for viral stability outside of a host. As sentinels of ocean health, marine mammals provide critical early insights on the ways in which pathogens may exploit changing ecological conditions. Using influenza infection of pinnipeds as a model system, we seek to define the key parameters that impact both propagation of a pathogen within a resilient host, and transmission of that pathogen into a susceptible host.