Epidemiology is the study of the distribution (frequency, patterns in time and space) and determinants (causes, risk/protective factors) of health-related states and events (e.g., diseases) in specified populations. Epidemiology provides public health scientists and researchers with tools and methods to investigate the outbreak and spread of diseases in the populations from different perspectives. Epidemiological principles guide the public health decision-makers through the risk management process, how to effectively prevent from, control, and eventually eliminate diseases. In epidemiology, the patient is the community, and individuals are viewed collectively. We study epidemiology using a “One Health” approach, which focuses on the health of animals and humans within a common environment. A reasonable level of understanding of epidemiological concepts and methods is necessary for all public health sector workers, researchers, and policymakers. This course is intended to introduce key One Health and epidemiological concepts and research methods to enable graduate students to develop well-designed public health studies, critically appraise the relevant literature, quantify health-related events in populations, measure associations, evaluate diagnostic tools, and investigate diseases effectively.