By Thomas R. Frieden, M.D., M.P.H.

The field of public health aims to improve the health of as many people as possible as rapidly as possible. Since 1900, the average life span in the United States has increased by more than 30 years; 25 years of this gain have been attributed to public health advances.1,2 Globally, life expectancy doubled during the 20th century,3 largely as a result of reductions in child mortality attributable to expanded immunization coverage, clean water, sanitation, and other child-survival programs.4

Public health focuses on denominators — what proportion of all people who can benefit from an intervention actually benefit. Maximizing health requires contributions from many sectors of society, including broad social, economic, environmental, transportation, and other policies in which government plays key roles; involvement of civil society; innovation by the public and private sectors; and health care and public health action. Although there has sometimes been distrust and disrespect between the health care and public health fields,5 they are inevitably and increasingly interdependent; maximizing potential health gains is a defining challenge for both fields.


Building a Public Health Pyramid

To maximize impact, public health works at five levels (Figure 1Figure 1The Health Impact Pyramid.). At the first level — the base of the pyramid — are socioeconomic factors such as income, education, housing, and race. Although these factors are not diseases, both public health efforts and health care can have some effect on them — for example, through health insurance coverage that reduces poverty or through prevention of teen pregnancy to reduce the perpetuation of poverty. Immediately above the socioeconomic factors are traditional public health interventions that change the context to make default decisions the healthy choices (e.g., by providing clean drinking water). At the next level are long-lasting protective interventions, such as immunizations, that require only intermittent action by the health care system. Next are clinical interventions requiring long-term, daily care, such as blood-pressure control. The last level includes counseling and education, such as exhorting people to eat healthy food and be physically active. Each level is important, but interventions at the pyramid’s base generally improve health for more people, at lower unit cost, than those at the top.6

To increase the impact of clinical care on population health, improvements in the third and fourth levels need to be implemented more effectively. Blood-pressure control, which can save more lives than any other clinical intervention,7 is successful in only about half of Americans; nearly 90% of patients with uncontrolled hypertension have both health insurance and a regular source of care, and more than 80% have multiple contacts with the health system each year.8

To maximize health overall, both communicable and noncommunicable disease threats need to be addressed in the United States and globally. There are important connections between infectious and noninfectious diseases: most cases of cervical cancer and many cases of liver cancer can now be prevented through vaccination; diabetes, obesity, and tobacco and alcohol use increase risks of both cancer and infections. U.S. and global health are also inextricably connected, as outbreaks of Ebola virus disease and the Middle East respiratory syndrome (MERS) and the spread of drug resistance make clear. Nevertheless, it is useful to give separate consideration to ways of addressing infectious and noninfectious conditions.

Infectious Diseases in the United States

Despite progress over the past century, the United States continues to face substantial infectious disease challenges. Human immunodeficiency virus (HIV) infection, hepatitis C virus infection, drug-resistant bacteria, health care–associated infections, and preventable influenza and pneumonia continue to kill more than 100,000 people in the United States each year.9-11 The increase in drug resistance, higher prevalence of risk factors such as diabetes and obesity, aging of the population, and greater complexity of medical interventions make infectious-disease control increasingly important and challenging. Addressing these challenges requires a combination of technological advances, more effective clinical and administrative systems, and political commitment to invest in prevention and control.

From a public health perspective, an effective clinical system has five essential characteristics: consistency, patient-centeredness, team-based care, registry-based information systems, and continuous improvement in treatments and delivery. These core features can help clinical systems address infectious-disease threats through standardization of care, interventions that increase patient adherence, team-based approaches to care (including hospital stewardship programs),12 rigorous monitoring of outcomes, and continuous improvement in detection, treatment, and prevention. Standardization and team-based care can increase vaccination rates and reduce prescription of unnecessary or overly broad-spectrum antibiotics. Registry-based approaches have the potential to increase the proportion of patients with HIV infection who are effectively treated from the current rate of 40% or less in the United States.13 Coordination among health care facilities and public health departments can substantially reduce the spread of drug resistance.14

Technological advances present new opportunities for infectious-disease control. These include large-scale, real-time whole-genome sequencing, which can improve identification of organisms, resistance, and infection clusters and elucidate the effects of the microbiome on health. New technologies complement and enhance but do not replace core epidemiologic functions.