Genetic epidemiology examines how genetic variation contributes to disease patterns within populations.

This chapter explores the methods used to identify inherited risk factors and gene–environment interactions. It bridges molecular biology and epidemiology, applying population-based designs to questions of genetic susceptibility.

We examine:

* Family-based…

Clinical epidemiology bridges two worlds: population science and individual patient care.

This chapter explores how epidemiological principles are applied to improve diagnosis, prognosis, and treatment decisions in clinical settings.

We examine:

* Measures of diagnostic accuracy (sensitivity, specificity)

* Predictive values and disease prevalence

* Likelihood rat…

Community-based intervention trials in low- and middle-income countries (LMICs) operate within contexts of limited infrastructure, variable resources, and diverse cultural settings.

This chapter explores how large-scale public health interventions are designed and evaluated when formal health systems may be fragmented or unevenly distributed.

We examine t…

Community intervention trials in high-income countries often operate within structured health systems, established institutions, and robust regulatory frameworks. This chapter examines how large-scale public health strategies are designed, implemented, and evaluated in these settings.

We explore classic and contemporary examples of community-based trials…

Some public health interventions cannot be delivered to individuals in isolation. Vaccination campaigns, water fluoridation, health promotion strategies, school-based programmes, and environmental modifications operate at the level of communities.

This chapter explores the methodological challenges of community intervention trials, also known as cluster …

Observational studies suggest associations. Intervention trials test them.

This chapter examines the methodology of individual-level intervention trials - most notably the randomised controlled trial (RCT), often regarded as the gold standard for evaluating effectiveness.

We explore the core components of trial design:

* Clear definition of intervention and …

If case–control studies look backward from outcome to exposure, cohort studies begin with exposure and move forward in time to observe outcome.

This chapter explores the structure and analytic power of cohort designs.

A cohort study identifies groups based on exposure status and follows them prospectively - or retrospectively through existing records - to…

Case–control studies reverse the usual direction of inquiry.

Instead of following exposed individuals forward in time, we begin with those who already have the outcome (cases) and compare them to those who do not (controls). We then look backward to assess prior exposure.

This chapter explores the design, strengths, and limitations of case–control methodo…

An outbreak transforms epidemiology from analysis into action.

This chapter outlines the structured approach to investigating suspected outbreaks - a disciplined sequence designed to identify the source, interrupt transmission, and prevent recurrence.

We walk through the classic steps:

* Confirm the existence of an outbreak

* Verify the diagnosis

* Define and iden…

Cross-sectional studies capture populations at a specific point in time. They measure exposure and outcome simultaneously, offering a “snapshot” of health status.

This chapter explores the design, utility, and limitations of cross-sectional analysis.

These studies are foundational for:

* Estimating prevalence of disease

* Describing distribution across demograp…