Epidemiology is the study of the incidence and patterns of disease with a view to finding means of prevention or control. Traditionally, epidemiological methods were applied to communicable diseases – those, such as cholera or measles, that can be passed from one person to another. However, modern epidemiology is equally concerned with the role of environmental and lifestyle factors in disease causation: for example, the link between lung cancer or between asbestos and the cancer known as mesothelioma.