Abstract
In this primer, we will review the key distinctions between acute and chronic infections, between mono- and polymicrobial infections and how these distinctions work together to generate the growing crisis of chronic polymicrobial infections. Chronic (non-resolving) infections place a large and growing burden on human health, globally. Following an introduction to the basic properties of chronic polymicrobial infections, we will use an ecological and evolutionary perspective to help outline a research agenda for this field, flagging both challenges and opportunities for improved infection prevention, diagnosis and treatment.