What Is Public Health? Research Areas, Funding, and Career Paths

Public health is the science and practice of protecting and improving the health of populations — entire communities, countries, or the world — rather than treating one patient at a time. Where clinical medicine asks “what is wrong with this patient and how do we treat it,” public health asks “what is making groups of people sick, injured, or die prematurely, and what can be changed — in policy, environment, behavior, or health systems — to prevent it.” This guide covers what public health actually studies, its major sub-disciplines, the real research funding landscape for the field, the methods practitioners and researchers use, and typical training and career pathways — the research-administration layer that a general encyclopedia entry on public health usually leaves out.

What public health actually studies

Public health is often summarized by three core functions first articulated in the U.S. Institute of Medicine’s 1988 report The Future of Public Health: assessment (systematically collecting and analyzing data on a population’s health status), policy development (using that evidence to shape laws, regulations, and programs), and assurance (making sure services that protect health are actually available and accessible). Around that framework, public health work spans a wide range of subject matter:

• Disease patterns. Why does a disease cluster in a particular place, time, or group, and what can interrupt that pattern — whether it’s an infectious outbreak, a chronic-disease trend, or an injury pattern.
• Environmental and occupational exposures. How air, water, food, chemicals, the built environment, and workplace conditions affect health at a population scale.
• Health behavior and social determinants. How income, education, housing, discrimination, and access to care shape health outcomes independently of any individual’s choices or genetics.
• Health systems and policy. How health care is organized, financed, regulated, and delivered, and how those structural choices affect population-level outcomes and equity.
• Preparedness and response. How communities and health systems plan for, detect, and respond to outbreaks, disasters, and other population-level health emergencies.

Public health is inherently interdisciplinary rather than a single method or body of theory. It draws its methods from biostatistics and epidemiology, its subject matter from medicine and biology, its behavioral models from psychology and sociology, and its intervention logic from policy analysis and health economics — see CASRAI’s guides to epidemiology, biology, and sociology for the neighboring disciplines it draws most heavily on. What distinguishes public health from any one of those parent fields is its consistent unit of analysis: the population, not the individual, and its consistent goal: prevention rather than treatment.

Major sub-disciplines within public health

Most schools and programs of public health organize their curricula and research around a small set of core disciplines, sometimes called the “five pillars” of public health education:

• Epidemiology. The study of how disease and health outcomes are distributed in populations and what factors explain that distribution — the core diagnostic discipline of public health. See CASRAI’s dedicated guide: What Is Epidemiology?
• Biostatistics. The statistical methods used to design public health studies and analyze population health data — sample size and power calculations, survival analysis, regression modeling, and the handling of clustered or longitudinal data.
• Environmental and occupational health. How physical, chemical, and biological hazards in air, water, soil, food, and workplaces affect health, and how exposure is measured and regulated.
• Health policy and management. How health systems, insurance structures, and regulation are designed and financed, and how policy choices translate into population health outcomes.
• Social and behavioral sciences (community health). How social context, culture, and individual behavior interact to shape health, and how programs are designed to change behavior or address structural conditions at a community level.

Beyond these five, most programs also offer more specialized tracks, including global health (population health work across national borders, often in low-resource settings), maternal and child health, health education and promotion, and public health nursing. A closely related applied discipline is implementation science, which studies how to actually get evidence-based interventions adopted and sustained in real-world settings rather than just proving they work in a controlled study — see CASRAI’s dictionary entry on implementation science.

The funding landscape for public health research

Public health research and practice in the United States is funded through a mix of federal agencies and a small number of large private foundations, each with a distinct role:

• National Institutes of Health (NIH). Several NIH institutes fund public-health-relevant research even though NIH’s overall mission is biomedical: the National Institute of Environmental Health Sciences (NIEHS) funds environmental exposure research; the National Institute on Minority Health and Health Disparities (NIMHD) funds research on health inequities; the Fogarty International Center funds global health research training; and institutes such as the National Cancer Institute (NCI) and National Heart, Lung, and Blood Institute (NHLBI) fund large population-level prevention and surveillance studies within their disease areas. Grant applicants writing for NIH audiences should see CASRAI’s guide on the NIH Project Narrative and Public Health Relevance Statement.
• Centers for Disease Control and Prevention (CDC). CDC is the primary federal agency funding applied public health practice and surveillance — disease surveillance systems, state and local health department capacity, outbreak investigation, and prevention programs — distinct from NIH’s more basic-science-oriented research funding.
• Agency for Healthcare Research and Quality (AHRQ) and the Health Resources and Services Administration (HRSA). AHRQ funds health services and health systems research; HRSA funds workforce development and access-to-care programs, particularly for underserved populations.
• Private foundations. The Robert Wood Johnson Foundation is the largest U.S. foundation dedicated specifically to health, funding both research and applied programs on health equity and access — see CASRAI’s guide on Robert Wood Johnson Foundation Grants. In global health specifically, the Bill & Melinda Gates Foundation and Bloomberg Philanthropies are major funders of population-level disease prevention and control work — see CASRAI’s guides on Gates Foundation research grant programs and Bloomberg Philanthropies’ research and public health grantmaking model.

Unlike NIH-heavy biomedical fields, public health research funding is genuinely split across several federal agencies with different mandates (research vs. practice vs. workforce vs. access) rather than concentrated in one primary funder — a distinction worth understanding before assuming an NIH-style mechanism applies to a CDC or HRSA award.

Research methods and tools

Public health research draws on a defined set of study designs and data infrastructure, most of them shared with epidemiology and biostatistics:

• Observational study designs. Cohort studies follow a defined group over time to see who develops an outcome, and case-control studies work backward from an outcome to compare exposure history between affected and unaffected groups — see CASRAI’s guides on cohort studies and case-control studies. Both are far more common in public health than randomized trials, since exposures like pollution, poverty, or diet usually cannot be ethically or practically randomized.
• Surveillance systems. Ongoing, systematic collection of health data — disease registries, notifiable-disease reporting, syndromic surveillance — that lets agencies detect and track outbreaks and trends in near-real time, rather than waiting for a dedicated study.
• Community trials and program evaluation. When an intervention (a vaccination campaign, a policy change, a screening program) can be tested, public health researchers often use community-level or cluster-randomized designs and formal program-evaluation frameworks rather than individually randomized clinical trials.
• Biostatistical and geospatial analysis. Regression modeling, survival analysis, and geographic information systems (GIS) mapping are standard tools for identifying spatial and temporal patterns in population health data.
• Human subjects protections. Because most public health research involves identifiable or potentially identifiable people, it is subject to the same IRB review and human-subjects protections as clinical research — see CASRAI’s dictionary entry on the IRB (Institutional Review Board) and guide on the human subjects research determination process, which walks through when a public health data-collection activity counts as regulated research versus routine public health practice.

Career and training pathways

The standard professional credential in the field is the Master of Public Health (MPH), typically a two-year graduate degree covering the five core disciplines above plus a practicum and culminating capstone project. Research-focused careers — academic faculty positions, senior roles at federal agencies, or leadership in research-heavy nonprofits — more often require a Doctor of Public Health (DrPH), oriented toward applied leadership and practice, or a PhD in a specific discipline such as epidemiology or biostatistics, oriented toward original research.

In the United States, accredited schools and programs of public health are reviewed by the Council on Education for Public Health (CEPH), the recognized accrediting body for the field. Graduates can pursue the Certified in Public Health (CPH) credential, administered by the National Board of Public Health Examiners, which functions as a voluntary professional certification rather than a state license (unlike, say, medicine or nursing). The American Public Health Association (APHA) is the field’s largest professional society, publishing the American Journal of Public Health and convening the discipline’s major annual meeting.

Typical employers span government (CDC, state and local health departments, HRSA, international bodies such as the World Health Organization), academia, and a large nonprofit and philanthropic sector working on health equity, global health, and health policy — a broader mix of employer types than most single academic disciplines, reflecting public health’s identity as an applied, practice-oriented field as much as a research one.

Frequently asked questions

What is the difference between public health and medicine?

Medicine treats individual patients who are already sick or injured. Public health works to prevent illness and injury across whole populations in the first place, often by changing environments, policies, or systems rather than treating any one person. The two fields overlap heavily — a physician diagnosing a cluster of cases and a public health investigator tracing an outbreak are often working the same problem from different ends — but their primary unit of concern differs: the patient versus the population.

What degree do you need to work in public health?

Entry-level public health roles often accept a bachelor’s degree, but the standard professional credential is the Master of Public Health (MPH). Research- and leadership-track roles typically require a Doctor of Public Health (DrPH) or a discipline-specific PhD (commonly in epidemiology or biostatistics).

What is the difference between an MPH and a DrPH?

An MPH is a generalist professional master’s degree, usually completed in two years, that covers the core disciplines of public health plus a practicum. A DrPH is a doctoral degree focused on applied leadership and advanced practice in the field, distinct from a research-focused PhD in a specific public health discipline.

Who funds public health research?

In the United States, public health research and practice are funded across several federal agencies with different mandates — NIH institutes such as NIEHS and NIMHD fund more basic and disparities-focused research, CDC funds applied surveillance and practice, and AHRQ and HRSA fund health-services and workforce/access work — plus major private foundations such as the Robert Wood Johnson Foundation (domestic health) and the Gates Foundation and Bloomberg Philanthropies (global health).

Is public health a science?

Yes — public health is a scientific field that uses epidemiology, biostatistics, and other empirical methods to study population-level health, but it is also explicitly an applied and policy-oriented practice, not a purely theoretical science. Most academic programs describe it as spanning both the science and the practice of protecting population health.

Related CASRAI resources

Public health sits at the intersection of several other disciplines covered in CASRAI’s branches-of-science series. See the full index at Branches of Science: A Complete Guide to Scientific Disciplines and Research Fields, and related guides on epidemiology, biology, and sociology.