This course examines the relationship between microbe and host; with particular focus on bacterial and viral pathogens. The diversity of structure, function and metabolism of bacteria, in relation to their role as a cause of disease, is explored and practical skills in bacteriology are introduced. Morphology and reproductive strategies of viruses are examined and methods for controlling viral infections by vaccination or anti-viral therapies are described. The course introduces principles of clinical microbiology by focusing on epidemiology, diagnosis, treatment of infection and host immune defences. The theme is one of "emergence" illustrating how some new infections have come to be a problem in health care and the importance of protective commensal microbes. The laboratory classes focus on diagnostic processes and illustrate the contribution which the microbiology laboratory can make to clinical decision making and epidemiology. This course also deals with the way in which pathogens (mainly bacteria) survive, and sometimes grow, in the environment and the implications this has for health in the community. The course is given in collaboration with health service consultants and workers from the University Hospitals of Morecambe Bay NHS Trust.