Meeting Summary: This working group explores the role of aging and adaptation in infectious diseases operating over multiple organizational and temporal scales. General areas include immune system dynamics and age, host-pathogen co-adaptation in chronic vs. acute infections, pathogen antigenic diversity and endemism, effects of age on infectious diseases in human and nonhuman hosts. Overarching themes include memory, (co)adaptation, diversity, feedback, robustness and fragility. We are interested in aging and biological time as reflecting a loss of robustness in the face of infection at the level of individuals but also populations. We are also interested in aging of the pathogen in relation to its ability to persist and withstand intervention efforts. This meeting brings together a select group of scientists from a range of backgrounds to define novel questions, facilitate potential collaborations, and catalyze new and transformative research in this area. Development of methods that combine big data, experiments, theory, and computation with predictive and therapeutic applications across disciplines is of particular interest.