Background
The dramatic increase in the average life span during the 20th century is widely credited to public health achievements, such as vaccination programs and control of many infectious diseases including polio, diphtheria, yellow fever, and smallpox; effective health and safety policies such as road traffic safety and occupational safety; improved family planning; tobacco control measures; and programs designed to decrease non-communicable diseases by acting on known risk factors such as a person's background, lifestyle and environment.
One of the major sources of the increase in average life span in the early 20th century was the decline in the urban penalty brought on by improvements in sanitation. These improvements included chlorination of drinking water, filtration, and sewage treatment, which led to the decline in deaths caused by infectious waterborne diseases such as cholera and intestinal diseases. Cutler and Miller in "The Role of Public Health Improvements in Health Advances" demonstrate how typhoid fever deaths in Chicago, Baltimore, Cincinnati, and Cleveland declined after these American cities adopted chlorination, filtration, and sewage treatment.
Since the 1980s, the growing field of population health has broadened the focus of public health from individual behaviors and risk factors to population-level issues such as inequality, poverty, and education. Modern public health is often concerned with addressing determinants of health across a population. There is recognition that our health is affected by many factors including where we live, genetics, income, education and social relationships - these are known as the social determinants of health. A social gradient in health runs through society, with those who are poorest generally suffering poor health. However even those in the middle classes will generally have poorer health than those of a higher social stratum. Newer public health policies seeks to address these health inequalities by advocating for population-based policies that improve health in an equitable manner.
Additionally, with the onset of the epidemiological transition and as the prevalence of infectious diseases decreased through the 20th century, the focus of public health has recently turned to chronic diseases such as cancer and heart disease.
Public Health and the Government
Public health plays an important role in disease prevention efforts in both the developing world and in developed countries, through local health systems and non-governmental organizations. The World Health Organization (WHO) is the international agency that coordinates and acts on global public health issues. Most countries have their own government public health agencies , sometimes known as ministries of health, to respond to domestic health issues. For example in the United States, the front line of public health initiatives is state and local health departments. The United States Public Health Service (PHS), led by the Surgeon General of the United States, and the Centers for Disease Control and Prevention, headquartered in Atlanta, are involved with several international health activities, in addition to their national duties. In Canada, the Public Health Agency of Canada is the national agency responsible for public health, emergency preparedness and response, and infectious and chronic disease control and prevention. The public health system in India is managed by the Ministry of Health & Family Welfare of the government of India with state owned health care facilities.
Public Health Nursing
Public health nursing made available through child welfare services.