Epidemiology is the study of the distribution and determinants of disease and health related events in populations. Unlike clinical medicine, which focuses on the health of individuals who come into healthcare facilities, epidemiology focuses on the health of entire communities. Epidemiologists investigate the frequency, pattern, causes, and risk factors of health-related events in order prevent disease and promote health. To do this, epidemiologists use statistical analysis to answer the who, what, when, and where questions related to a disease event. The answers to these questions help make recommendations to control the spread of disease events and prevent future occurrences.