What is epidemiology?

Epidemiology in its most basic definition is the study of patterns of disease within a given population. In addition to patterns, epidemiologists study the cause and effect that a disease has on a population. When I think about epidemiology, I think of the 1854 Broad Street cholera outbreak. John Snow was one of the first individuals to propose the germ theory of disease. The germ theory of disease suggests that diseases are caused by microorganisms that grow and reproduce within host organism. The germ theory of disease replaced the concept of "bad air." After talking to community members, Snow deduced that the source of the Cholera outbreak was the water pump on Broad Street. In a time where microorganisms had not been discovered, Snow was able to find a pattern of disease and locate the source. Below is a picture of the clusters of Cholera within Soho, London in 1854. His innovation has led the way for modern medicine. 

Although epidemiology is rooted in infectious disease, it also explores chronic disease and conditions such as diabetes, cancer, pregnancy and injury. The word epidemiology comes from the Greek words epi meaning "on", demos meaning "people" and ology meaning "the study of." Epidemiology relies on statistical analysis to calculate frequency and distribution of disease within a population. What interests me about epidemiology is that there is a greater focus on population health rather than individual health. I believe that a person's health is largely determined by their community. Intrinsic controls play a crucial role in lifestyle behaviors but extrinsic controls such as stress, poverty, and society can define an individuals health status. Epidemiology focuses on big picture and determines the cause of the disease or condition. For example, an individual can be treated for heart disease by a physician but an epidemiologist can study an entire population to identify the prevalence and cause of heart disease. That epidemiologist may find that there is a lack of physical education within the community and promote physical activity. In a way, epidemiology is a type of preventative care. If we can understand the cause of a disease or condition, we can better prepare that community for prevention.