Richard Skolnik, teaching Yale's Essentials of Global Health, covers the burden of disease framework used across global health work. He surveys the current state of world health, then walks through key demographic factors, fertility, mortality, population growth and age structure, and how these shape health outcomes across countries. The lecture closes by examining what people actually get sick from, become disabled by, and die of, tracing these conditions back to underlying risk factors and determinants such as behavior, environment, and access to care. Skolnik uses data and comparative statistics across regions to show how demographic transitions change a population's disease burden over time, moving countries from patterns dominated by infectious disease toward those dominated by chronic and noncommunicable conditions. The session is built as a foundation for the rest of the course, giving students the vocabulary and data literacy needed before later sessions on specific diseases and health systems.