Epidemiology is the study of the distribution and patterns of heath-events, heath-characteristics and their causes or influence in well-defined populations. It is the cornerstone method of public health research and practice, and helps inform public decisions and evidence based medicine. The major areas of epidemiological study include disease etiology, outbreak investigation and disease surveillance. Other areas of study include bio monitoring, screening and comparisons of clinical trials. Epidemiology utilised many other scientific disciplines such as biology, biostatistics and social sciences.