Population health is the body of scientific disciplines interested in the study of the distribution and determinants of health and disease states in the population. It is an approach to health that seeks to step beyond the individual-level focus of traditional clinical and preventive medicine by addressing a broad range of factors that impact health on a population-level. For example, it can focus on ways to reduce health inequities among population groups by exploring factors such as the environment, social structures, resource distribution, etc.
Epidemiology is the scientific discipline primarily concerned with identifying the distribution and causes of disease in populations, and as such encompasses a rich methodology including observational and experimental study designs, statistical methods, an understanding of pathogens, environmental and behavioral risk factors, and human biology. Epidemiological methods have evolved to meet threats of global infectious diseases and the complex health challenges presented by an aging population, as well as to capitalize on the expanding understanding of human genetics. As the fundamental discipline of public health, epidemiology provides essential knowledge to design, implement, and assess approaches to effectively prevent disease and improve quality of life in the population.