The fourth edition includes: a thorough reorganisation of Section One, with an introduction to past and present issues in medical microbiology and the history of infectious diseases; new topics, such as avian influenza, Chikungunya virus and point of care testing; new case studies, including glandular fever diagnosis, Bairnsdale ulcer, congenital rubella, measles, whooping cough, avian influenza, cholera outbreak in Iraq, Shigellosis 2, and Murray Valley encephalitis; recent issues and guidelines in public health policy within Australia and New Zealand.