Infectious disease epidemiology studies how pathogens move through populations and what factors drive outbreaks and transmission. This book opens with core concepts—reservoirs, modes of transmission, incubation periods—and then builds practical skills in surveillance and outbreak investigation. It explains study designs used to measure incidence and risk, from cohort studies to case–control investigations, with real-world examples. Chapters on modelling and genomic epidemiology show how modern tools refine contact tracing and predict spread. There are practical sections on vaccination impact assessment, antimicrobial resistance surveillance, and ethical issues in outbreak response. Designed for public-health trainees, clinicians, and policy-makers, it balances theory with action-oriented guidance.