What is public health?

Health care is vital to all of us some of the time, but public health is vital to all of us all of the time.
—C. Everett Koop, former U.S. surgeon general

Health is a state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity.
—World Health Organization

Public health is the science of protecting and improving the health of populations—from neighborhoods to cities to countries to world regions—through education, promotion of healthy lifestyles, research toward prevention of disease and injury, and detecting, preventing, and responding to infectious diseases. Public health experts analyze the effect on health of genetics, personal choice, and the environment to develop interventions and policies that protect the health of families and communities, such as vaccination programs and education on the dangers of tobacco and alcohol. As the American Public Health Association notes, “Public health saves money, improves our quality of life, helps children thrive, and reduces human suffering.”

Public health professionals try to prevent problems from happening or recurring through implementing educational programs, recommending policies, administering services, and conducting research—in contrast to clinical professionals like doctors and nurses, who focus primarily on treating individuals after they become sick or injured. Public health also works to limit health disparities. A large part of public health is promoting health care equity, quality, and accessibility.
—CDC Foundation

Academic disciplines involved in public health

The field of public health is highly varied and encompasses many academic disciplines, including the following:

Behavioral science/Health education


Environmental health


Health policy

Health services administration/management

Humanitarian and human rights studies

Immunology, molecular biology, genetics, and other basic sciences

International health/global health

Maternal and child health


Public health laboratory practice (e.g., testing of biological and environmental samples)

Public health practice

Public health occupations

Some examples of the many occupations involved in public health include:

Scientists and researchers


Public health leaders and policymakers

Public health physicians

Public health nurses

Occupational health and safety professionals


Social workers

Community planners

Health educators

First responders

Restaurant inspectors

Sanitarians (investigate health and safety within an environment, enforce health and safety regulations, and identify risk factors)

Activities of public health professionals

Some examples of the work undertaken by public health professionals include:

Studying environmental toxins and their health impacts

Monitoring the quality of the air we breathe and the water we drink

Developing plans and strategies to respond to emergencies and disasters

Exploring the causes of injuries and how best to prevent them

Testing biological and environmental samples

Researching risk factors for chronic disease and designing, implementing, and evaluating programs for reducing those risk factors

Implementing childhood and adult vaccination programs

Improving care for pregnant women, mothers, and newborns

Promoting healthy eating and physical activity

Ensuring access to a high-quality fruit and vegetable supply

Investigating infectious-disease outbreaks

Analyzing data for health trends

Undertaking screening programs for certain cancers

Analyzing and implementing public health policy

Principal tools of public health research

Population and numeric disciplines—especially epidemiology, biostatistics, and informatics

Biological sciences disciplines—focusing on infectious and chronic diseases as well as nutritional and environmental links to ill health. Largely laboratory based, and emphasizing the biological, chemical, and genetic basis of health and disease.

Social and policy disciplines—including health policy and management, global health systems, health economics, and the social and behavioral determinants of health and disease

Distinctions between public health and medicine

Because of their shared concern with human health, people often are confused by the difference between public health and medicine. In fact, people’s health is shaped much more by their lifestyle, social networks, environment, and genes than by medical care. Below are some specific distinctions between public health and medicine.

Public health

Primary focus on populations

Emphasis on disease prevention and health promotion for entire communities

Predominant emphasis on promoting healthy behaviors and environments

Specializations organized, for example, by analytical method (epidemiology, toxicology); setting and population (occupational health, global health); substantive health problem (environmental health, nutrition)

Biological sciences central, with a prime focus on major threats to the health of populations, such as epidemics and noncommunicable diseases; research moves between laboratory and field

Social and public policy disciplines an integral part of public health education


Primary focus on individuals

Emphasis on disease diagnosis, treatment, and care of the individual patient

Predominant emphasis on medical care

Specializations organized, for example, by organ system (cardiology, neurology); patient group (obstetrics, pediatrics); etiology and pathophysiology (infectious disease, oncology); technical skill (radiology, surgery)

Biological sciences central, stimulated by needs of patients; research moves between laboratory and bedside

Social sciences generally an elective part of medical education

Leading causes of death in the United States

Medical view (focuses on the diseases that actually cause deaths)

Heart disease



Chronic lower respiratory diseases

Stroke (cerebrovascular diseases)

Source: Deaths and Mortality, National Center for Health Statistics, Centers for Disease Control and Prevention 

Much of this health burden could be prevented or postponed through improved nutrition, increased physical activity, improved vaccination rates, avoidance of tobacco use, adoption of measures to increase motor-vehicle safety, early detection and treatment of risk factors, and health-care quality improvement.
CDC National Health Report: Leading Causes of Morbidity and Mortality and Associated Behavioral Risk and Protective Factors—United States, 2005–2013

Public health view (focuses on the factors that lead to deadly diseases)

Tobacco use

Poor diet

Physical inactivity


Infectious disease

Social determinants of health

“Social determinants of health”—a term often used in the public health field—refers to the conditions in which people are born, grow, work, live, and age and the wider set of forces and systems shaping the conditions of daily life, as defined by the World Health Organization (WHO). These social determinants may describe social inequities that are reflected in the poor health of certain populations, often with devastating consequences. WHO, as noted in its report Health Equity Through Action on the Social Determinants of Health, believes that reducing health inequities is an ethical imperative. “Social injustice,” the report notes, “is killing people on a grand scale.”

Examples of social determinants include:

Availability of resources to meet daily needs (e.g., safe housing and local food markets)

Access to educational, economic, and job opportunities

Access to health care services

Quality of education and job training

Availability of community-based resources in support of community living and opportunities for recreational and leisure-time activities

Transportation options

Public safety

Social support

Social norms and attitudes (e.g., discrimination, racism, and distrust of government)

Exposure to crime, violence, and social disorder (e.g., presence of trash and lack of cooperation in a community)

Socioeconomic conditions (e.g., concentrated poverty and the stressful conditions that accompany it)

Residential segregation


Access to mass media and emerging technologies (e.g., cell phones, the Internet, and social media)


Source: Healthy People 2020

People’s health is determined in part by access to social and economic opportunities; the resources and supports available in their homes, neighborhoods, and communities; the quality of their schooling; the safety of their workplaces; the cleanliness of their water, food, and air; and the nature of their social interactions and relationships. Social determinants of health involve economic stability, education, social and community context, health, health care, neighborhood, and the built environment. Each of these five determinant areas reflects a number of key issues that make up the underlying factors in the arena of social determinants of health.

Economic stability


Food insecurity

Housing instability



Early childhood education and development

Enrollment in higher education

High school graduation

Language and literacy

Social and community context

Civic participation



Social cohesion

Health and health care

Access to health care

Access to primary care

Health literacy

Neighborhood and built environment

Access to foods that support healthy eating patterns

Crime and violence

Environmental conditions

Source: Healthy People 2020

“The enjoyment of the highest attainable standard of health is one of the fundamental rights of every human being without distinction of race, religion, political belief, economic or social condition.” —Constitution of the World Health Organization, inscribed in several languages on the FXB Building of the Harvard T.H. Chan School of Public Health

Major global public health challenges

Ending disparities in health between rich and poor and across racial and gender lines

Reducing infant mortality, maternal death rates, and reproductive health problems

Developing solutions and treatments for infectious diseases (e.g., AIDS, tuberculosis, and malaria)

Tackling malnutrition

Preventing the spread of multi-drug-resistant (MDR) diseases, such as MDR tuberculosis

Confronting emerging threats to health from chronic diseases such as diabetes, heart disease, and obesity that are related to lifestyle (e.g., diet, exercise, and tobacco use)

Addressing mental illnesses and social factors in health

Understanding climate change and other environmental health threats

Studying the impacts of war, violence, and terrorism on health

Advancing practices, protocols, and strategies to achieve diverse goals, such as reducing surgical errors, changing social norms around drunk driving

Developing health and communications systems to improve health-related policy and decision-making and increase the speed and effectiveness of responses to emergencies such as disease pandemics, natural disasters, or terrorist attacks

Ten great public health achievements in the United States, 1900–1999

1. Vaccination

Programs of population-wide vaccinations resulted in the eradication of smallpox; elimination of polio in the Americas; and control of measles, rubella, tetanus, diphtheria, Haemophilus influenzae type b, and other infectious diseases in the United States and other parts of the world.

2. Motor-vehicle safety

Improvements in motor-vehicle safety have contributed to large reductions in motor-vehicle-related deaths. These improvements include engineering efforts to make both vehicles and highways safer and successful efforts to change personal behavior (e.g., increased use of safety belts, child safety seats, motorcycle helmets, and decreased drinking and driving).

3. Safer workplaces

Work-related health problems, such as coal workers’ pneumoconiosis (black lung), and silicosis—common at the beginning of the century— have been significantly reduced. Severe injuries and deaths related to mining, manufacturing, construction, and transportation also have decreased; since 1980, safer workplaces have resulted in a reduction of approximately 40% in the rate of fatal occupational injuries.

4. Control of infectious diseases

Control of infectious diseases has resulted from clean water and better sanitation. Infections such as typhoid and cholera, major causes of illness and death early in the 20th century, have been reduced dramatically by improved sanitation. In addition, the discovery of antimicrobial therapy has been critical to successful public health efforts to control infections such as tuberculosis and sexually transmitted diseases (STDs).

5. Decline in deaths from coronary heart disease and stroke

Decline in deaths from coronary heart disease and stroke have resulted from risk-factor modification, such as smoking cessation and blood pressure control coupled with improved access to early detection and better treatment. Since 1972, death rates for coronary heart disease have decreased 51 percent.

6. Safer and healthier foods

Since 1900, safer and healthier foods have resulted from decreases in microbial contamination and increases in nutritional content. Identifying essential micronutrients and establishing food-fortification programs have almost eliminated major nutritional deficiency diseases such as rickets, goiter, and pellagra in the United States. [Healthy Eating Plate sidebar]

7. Healthier mothers and babies

Healthier mothers and babies are a result of better hygiene and nutrition, availability of antibiotics, greater access to health care, and technological advances in maternal and neonatal medicine. Since 1900, infant mortality has decreased 90 percent, and maternal mortality has decreased 99 percent.

8. Family planning

Access to family planning and contraceptive services has altered social and economic roles of women. Family planning has provided health benefits such as smaller family size and longer intervals between the birth of children; increased opportunities for preconceptional counseling and screening; fewer infant, child, and maternal deaths; and the use of barrier contraceptives to prevent pregnancy and transmission of human immunodeficiency virus and other STDs.

9. Fluoridation of drinking water

Fluoridation of drinking water began in 1945 and in 1999 reaches an estimated 144 million persons in the United States. Fluoridation safely and inexpensively benefits both children and adults by effectively preventing tooth decay, regardless of socioeconomic status or access to care. Fluoridation has played an important role in the reductions in tooth decay (40 percent to 70 percent in children) and of tooth loss in adults (40 percent to 60 percent).

10. Recognition of tobacco use as a health hazard

Recognition of tobacco use as a health hazard in 1964 has resulted in changes in the promotion of cessation of use, and reduction of exposure to environmental tobacco smoke. Since the initial Surgeon General’s report on the health risks of smoking, the prevalence of smoking among adults has decreased, and millions of smoking-related deaths have been prevented.

Source: Centers for Disease Control and Prevention, Morbidity and Mortality Weekly Report

Ten great public health achievements in the United States, 2001–2010

During the 20th century, life expectancy at birth among U.S. residents increased by 62%, from 47.3 years in 1900 to 76.8 in 2000, and unprecedented improvements in population health status were observed at every stage of life. In 1999, the CDC’s Morbidity and Mortality Weekly Report published a series of reports highlighting 10 public health achievements that contributed to those improvements. This report assesses advances in public health during the first 10 years of the 21st century. Public health scientists at the CDC were asked to nominate noteworthy public health achievements that occurred in the United States during 2001–2010. From those nominations, 10 achievements, not ranked in any order, have been summarized in this report.
Centers for Disease Control and Prevention, Morbidity and Mortality Weekly Report

1. Vaccine-preventable diseases

The decade saw substantial declines in cases, hospitalizations, deaths, and health-care costs associated with vaccine-preventable diseases. New vaccines (i.e., rotavirus, quadrivalent meningococcal conjugate, herpes zoster, pneumococcal conjugate, and human papillomavirus vaccines, as well as tetanus, diphtheria, and acellular pertussis vaccine for adults and adolescents) were introduced, bringing to 17 the number of diseases targeted by U.S. immunization policy. A recent economic analysis indicated that vaccination of each U.S. birth cohort with the current childhood immunization schedule prevents approximately 42,000 deaths and 20 million cases of disease, with net savings of nearly $14 billion in direct costs and $69 billion in total societal costs.

The impact of two vaccines has been particularly striking. Following the introduction of pneumococcal conjugate vaccine, an estimated 211,000 serious pneumococcal infections and 13,000 deaths were prevented during 2000–2008. Routine rotavirus vaccination, implemented in 2006, now prevents an estimated 40,000–60,000 rotavirus hospitalizations each year. Advances also were made in the use of older vaccines, with reported cases of hepatitis A, hepatitis B, and varicella at record lows by the end of the decade. Age-specific mortality (i.e., deaths per million population) from varicella for persons age <20 years, declined by 97% from 0.65 in the prevaccine period (1990–1994) to 0.02 during 2005–2007. Average age-adjusted mortality (deaths per million population) from hepatitis A also declined significantly, from 0.38 in the prevaccine period (1990–1995) to 0.26 during 2000–2004.

2. Prevention and control of infectious diseases

Improvements in state and local public health infrastructure along with innovative and targeted prevention efforts yielded significant progress in controlling infectious diseases. Examples include a 30% reduction from 2001 to 2010 in reported U.S. tuberculosis cases and a 58% decline from 2001 to 2009 in central line–associated blood stream infections. Major advances in laboratory techniques and technology and investments in disease surveillance have improved the capacity to identify contaminated foods rapidly and accurately and prevent further spread. Multiple efforts to extend HIV testing, including recommendations for expanded screening of persons aged 13–64 years, increased the number of persons diagnosed with HIV/AIDS and reduced the proportion with late diagnoses, enabling earlier access to life-saving treatment and care and giving infectious persons the information necessary to protect their partners. In 2002, information from CDC predictive models and reports of suspected West Nile virus transmission through blood transfusion spurred a national investigation, leading to the rapid development and implementation of new blood donor screening. To date, such screening has interdicted 3,000 potentially infected U.S. donations, removing them from the blood supply. Finally, in 2004, after more than 60 years of effort, canine rabies was eliminated in the United States, providing a model for controlling emerging zoonoses.

3. Tobacco control

Since publication of the first Surgeon General’s Report on tobacco in 1964, implementation of evidence-based policies and interventions by federal, state, and local public health authorities has reduced tobacco use significantly. By 2009, 20.6% of adults and 19.5% of youths were current smokers, compared with 23.5% of adults and 34.8% of youths 10 years earlier. However, progress in reducing smoking rates among youths and adults appears to have stalled in recent years. After a substantial decline from 1997 (36.4%) to 2003 (21.9%), smoking rates among high school students remained relatively unchanged from 2003 (21.9%) to 2009 (19.5%). Similarly, adult smoking prevalence declined steadily from 1965 (42.4%) through the 1980s, but the rate of decline began to slow in the 1990s, and the prevalence remained relatively unchanged from 2004 (20.9%) to 2009 (20.6%). Despite the progress that has been made, smoking still results in an economic burden, including medical costs and lost productivity, of approximately $193 billion per year.

Although no state had a comprehensive smoke-free law (i.e., prohibit smoking in worksites, restaurants, and bars) in 2000, that number increased to 25 states and the District of Columbia (DC) by 2010, with 16 states enacting comprehensive smoke-free laws following the release of the 2006 Surgeon General’s Report. After 99 individual state cigarette excise tax increases, at an average increase of 55.5 cents per pack, the average state excise tax increased from 41.96 cents per pack in 2000 to $1.44 per pack in 2010. In 2009, the largest federal cigarette excise tax increase went into effect, bringing the combined federal and average state excise tax for cigarettes to $2.21 per pack, an increase from $0.76 in 2000. In 2009, the Food and Drug Administration (FDA) gained the authority to regulate tobacco products. By 2010, FDA had banned flavored cigarettes, established restrictions on youth access, and proposed larger, more effective graphic warning labels that are expected to lead to a significant increase in quit attempts.

4. Maternal and infant health

The past decade has seen significant reductions in the number of infants born with neural tube defects (NTDs) and expansion of screening of newborns for metabolic and other heritable disorders. Mandatory folic acid fortification of cereal grain products labeled as enriched in the United States beginning in 1998 contributed to a 36% reduction in NTDs from 1996 to 2006 and prevented an estimated 10,000 NTD-affected pregnancies in the past decade, resulting in a savings of $4.7 billion in direct costs.

Improvements in technology and endorsement of a uniform newborn-screening panel of diseases have led to earlier life-saving treatment and intervention for at least 3,400 additional newborns each year with selected genetic and endocrine disorders. In 2003, all but four states were screening for only six of these disorders. By April 2011, all states reported screening for at least 26 disorders on an expanded and standardized uniform panel. Newborn screening for hearing loss increased from 46.5% in 1999 to 96.9% in 2008. The percentage of infants not passing their hearing screening who were then diagnosed by an audiologist before age 3 months as either normal or having permanent hearing loss increased from 51.8% in 1999 to 68.1 in 2008.

5. Motor-vehicle safety

Motor vehicle crashes are among the top 10 causes of death for U.S. residents of all ages and the leading cause of death for persons aged 5–34 years. In terms of years of potential life lost before age 65, motor vehicle crashes ranked third in 2007, behind only cancer and heart disease, and account for an estimated $99 billion in medical and lost work costs annually. Crash-related deaths and injuries largely are preventable. From 2000 to 2009, while the number of vehicle miles traveled on the nation’s roads increased by 8.5%, the death rate related to motor vehicle travel declined from 14.9 per 100,000 population to 11.0, and the injury rate declined from 1,130 to 722; among children, the number of pedestrian deaths declined by 49%, from 475 to 244, and the number of bicyclist deaths declined by 58%, from 178 to 74.

These successes largely resulted from safer vehicles, safer roadways, and safer road use. Behavior was improved by protective policies, including effective seat belt and child safety seat legislation; 49 states and the DC have enacted seat belt laws for adults, and all 50 states and DC have enacted legislation that protects children riding in vehicles. Graduated drivers licensing policies for teen drivers have helped reduce the number of teen crash deaths.

6. Cardiovascular-disease prevention

Heart disease and stroke have been the first and third leading causes of death in the United States since 1921 and 1938, respectively. Preliminary data from 2009 indicate that stroke is now the fourth leading cause of death in the United States. During the past decade, the age-adjusted coronary heart disease and stroke death rates declined from 195 to 126 per 100,000 population and from 61.6 to 42.2 per 100,000 population, respectively, continuing a trend that started in the 1900s for stroke and in the 1960s for coronary heart disease. Factors contributing to these reductions include declines in the prevalence of cardiovascular risk factors such as uncontrolled hypertension, elevated cholesterol, and smoking, and improvements in treatments, medications, and quality of care.

7. Occupational safety

Significant progress was made in improving working conditions and reducing the risk for workplace-associated injuries. For example, patient lifting has been a substantial cause of low back injuries among the 1.8 million U.S. health-care workers in nursing care and residential facilities. In the late 1990s, an evaluation of a best practices patient-handling program that included the use of mechanical patient-lifting equipment demonstrated reductions of 66% in the rates of workers’ compensation injury claims and lost workdays and documented that the investment in lifting equipment can be recovered in less than 3 years. Following widespread dissemination and adoption of these best practices by the nursing home industry, Bureau of Labor Statistics data showed a 35% decline in low back injuries in residential and nursing care employees between 2003 and 2009.

The annual cost of farm-associated injuries among youth has been estimated at $1 billion annually. A comprehensive childhood agricultural injury prevention initiative was established to address this problem. Among its interventions was the development by the National Children’s Center for Rural Agricultural Health and Safety of guidelines for parents to match chores with their child’s development and physical capabilities. Follow-up data have demonstrated a 56% decline in youth farm injury rates from 1998 to 2009 (National Institute for Occupational Safety and Health, unpublished data, 2011).

In the mid-1990s, crab fishing in the Bering Sea was associated with a rate of 770 deaths per 100,000 full-time fishers. Most fatalities occurred when vessels overturned because of heavy loads. In 1999, the U.S. Coast Guard implemented Dockside Stability and Safety Checks to correct stability hazards. Since then, one vessel has been lost and the fatality rate among crab fishermen has declined to 260 deaths per 100,000 full-time fishers.

8. Cancer prevention

Evidence-based screening recommendations have been established to reduce mortality from colorectal cancer and female breast and cervical cancer. Several interventions inspired by these recommendations have improved cancer screening rates. Through the collaborative efforts of federal, state, and local health agencies, professional clinician societies, not-for-profit organizations, and patient advocates, standards were developed that have significantly improved cancer screening test quality and use. The National Breast and Cervical Cancer Early Detection Program has reduced disparities by providing breast and cervical cancer screening services for uninsured women. The program’s success has resulted from similar collaborative relationships. From 1998 to 2007, colorectal cancer death rates decreased from 25.6 per 100,000 population to 20.0 (2.8% per year) for men and from 18.0 per 100,000 to 14.2 (2.7% per year) for women. During this same period, smaller declines were noted for breast and cervical cancer death rates (2.2% per year and 2.4%, respectively).

9. Childhood lead-poisoning prevention

In 2000, childhood lead poisoning remained a major environmental public health problem in the United States, affecting children from all geographic areas and social and economic levels. Black children and those living in poverty and in old, poorly maintained housing were disproportionately affected. In 1990, five states had comprehensive lead poisoning prevention laws; by 2010, 23 states had such laws. Enforcement of these statutes as well as federal laws that reduce hazards in the housing with the greatest risks has significantly reduced the prevalence of lead poisoning. Findings of the National Health and Nutrition Examination Surveys from 1976–1980 to 2003–2008 reveal a steep decline, from 88.2% to 0.9%, in the percentage of children aged 1–5 years with blood lead levels ≥10 µg/dL. The risks for elevated blood lead levels based on socioeconomic status and race also were reduced significantly. The economic benefit of lowering lead levels among children by preventing lead exposure is estimated at $213 billion per year.

10. Public health preparedness and response

After the international and domestic terrorist actions of 2001 highlighted gaps in the nation’s public health preparedness, tremendous improvements have been made. In the first half of the decade, efforts were focused primarily on expanding the capacity of the public health system to respond (e.g., purchasing supplies and equipment). In the second half of the decade, the focus shifted to improving the laboratory, epidemiology, surveillance, and response capabilities of the public health system. For example, from 2006 to 2010, the percentage of Laboratory Response Network labs that passed proficiency testing for bioterrorism threat agents increased from 87% to 95%. The percentage of state public health laboratories correctly subtyping Escherichia coli O157:H7 and submitting the results into a national reporting system increased from 46% to 69%, and the percentage of state public health agencies prepared to use Strategic National Stockpile material increased from 70% to 98%. During the 2009 H1N1 influenza pandemic, these improvements in the ability to develop and implement a coordinated public health response in an emergency facilitated the rapid detection and characterization of the outbreak, deployment of laboratory tests, distribution of personal protective equipment from the Strategic National Stockpile, development of a candidate vaccine virus, and widespread administration of the resulting vaccine. These public health interventions prevented an estimated 5–10 million cases, 30,000 hospitalizations, and 1,500 deaths (CDC, unpublished data, 2011).

Existing systems also have been adapted to respond to public health threats. During the 2009 H1N1 influenza pandemic, the Vaccines for Children program was adapted to enable provider ordering and distribution of the pandemic vaccine. Similarly, President’s Emergency Plan for AIDS Relief clinics were used to rapidly deliver treatment following the 2010 cholera outbreak in Haiti.