Epidemiology is the branch of public health that deals with the study of the causes, distribution, and control of disease in populations. Distribution refers to the measurement of disease frequency, focusing on who is getting the disease and when and where the disease is occurring. When the patterns of a disease are understood, associated causal or preventive factors can then be determined. Epidemiologists are public health workers with diverse backgrounds and are mainly involved in designing methods to eradicate, eliminate, or minimize the impact of diseases, and disability in the society.