Human health is maintained by health professionals who apply the principles and processes of evidence-based medicine and compassion. Human illness, injury, and other physical and mental disabilities are studied, diagnosed, treated, and prevented by health professionals in accordance with the needs of the people they serve. They provide advice on or implement preventive and therapeutic actions, as well as promote health, with the ultimate goal of meeting individuals' and populations' health needs and expectations, and improving population health outcomes. They also do research to increase evidence-based health care by improving or developing concepts, theories, and operational procedures.