Public health, social determinants of health, and public policy

The growing importance of public health is evidenced by its increasing responsibilities. Public health was historically known for its contribution towards reduction and control of infectious diseases through such efforts as environmental sanitation (by securing safe air and water), hygienic practices, the elimination of smallpox and polio (through immunization), and reduction of overcrowding. As chronic diseases replaced infectious diseases as the leading causes of death, public health shifted its focus towards health promotion programs such as lifestyle changes in diet, tobacco, and exercise, to prevent contemporary health threats including cardiovascular disease, type-2 diabetes, and obesity. In recent years, as a result of a series of natural calamities such as Hurricanes Katrina and Rita and the spread of severe acute respiratory syndrome (SARS), and human-created threats such as 9-11 attack and the possibility of terrorist attacks involving chemical, biological, radiological, or nuclear weapons, public health has again assumed center stage and been called upon to handle these emerging threats. However, little is known about how the public health system can be organized to effectively and efficiently handle the modern-day threats of infectious and chronic diseases, and environmental disruptions, both natural and human-created. Moreover, public health remains marginal in many countries' health care system, particularly the US where public policy has rarely emphasized public health. There remains a deep lack of appreciation of what public health can accomplish towards improving population health.