The inhabitants in question can be as small as a handful of people or as large as all of the inhabitants of a number of continents . Public health has many sub-fields, however typically consists of the interdisciplinary classes of epidemiology, biostatistics and health services. [newline]Environmental health, community health, behavioral health, and occupational health are additionally important areas of public health. Public health additionally takes numerous actions to limit the health disparities between totally different areas of the nation and, in some cases, the continent or world. One concern is the access of individuals and communities to health care in phrases of financial, geographical or socio-cultural constraints.