Epidemiology vs. Public Health

By Dr. Jessica Sapp  |  08/10/2026

According to the World Health Organization® (WHO), “Health is a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity.” This concept demonstrates that a person’s health extends beyond healthcare, which encompasses the broader focus of public health.

Epidemiology also plays an important role and could be considered the center of public health. Epidemiology studies how diseases or disorders occur and spread within populations, as well as the causes of health problems and health disparities.  

What Is Public Health?

Public health aims to protect and improve the health of people and communities by providing the maximum health benefit for the largest number of people. In essence, public health can be impacted by anything that affects a person’s health such as:

• Housing
• Sanitation
• Nutrition
• Vaccination programs
• Disaster response

As explained by WHO, “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 professionals help to create health regulations. They typically involve various professionals such as public health administrators and health policy advocates.

What Is Epidemiology?

There are five core disciplines of public health, which are widely used in most public health programs. These disciplines include:

• Epidemiology
• Biostatistics
• Health policy and management
• Social and behavioral sciences
• Environmental health

Epidemiology is often referred to as the core science of public health, providing essential data and methods for tracking and preventing disease. According to scholar Cother Hajat,  epidemiology “is the study of the distribution and determinants of health-related states or events in specified populations and the application of this study to the prevention and control of health problems.”

Types of Epidemiology

Like public health, epidemiology includes a variety of specialties. Here are a few types of epidemiology specializations:

• Disaster epidemiology – According to the Centers for Disease Control and Prevention® (CDC),  disaster epidemiology “assesses the short- and long-term health effects of disasters to help guide emergency response, recovery efforts, and predict consequences of future disasters.”
• Infectious disease epidemiology – Author Dr. Susan Payne notes that infectious disease epidemiology (which includes the epidemiology of viruses) “is the study of the complex relationships among hosts and infectious agents.” Epidemiologists are interested in virus spread or transmission, with or without disease.
• Chronic disease epidemiology – According to the Council of State and Territorial Epidemiologists (CSTE®), chronic disease epidemiology is the branch of public health that studies the distribution, determinants, and natural history of long-term health conditions in populations. The role of a chronic disease epidemiologist is to collect, analyze, synthesize, and disseminate disease-specific information. That information includes medical, societal, and financial costs; spatial and temporal disease distribution; and risk factors or causes.
• Psychiatric epidemiology – According to scholars Li-Ching Lee, Rebecca Harrington, and William W. Eaton, psychiatric epidemiology is “the study of distribution, determinants, and causes of psychiatric conditions or mental health in human populations.” Rather than treating individual patients, researchers in this field analyze trends and risk factors across groups to inform public health strategies and policies.
• Behavioral epidemiology – According to an Epidemiological Science article, behavioral epidemiology “is a subfield of epidemiology.” It “focuses on the distribution and determinants of health-related behaviors within populations and the application of this knowledge to the prevention and control of health problems. It recognizes that individual and collective behaviors, such as tobacco use, dietary habits, physical activity levels, sexual practices, and adherence to medical recommendations, are significant contributors to the etiology, progression, and outcomes of a wide range of diseases and health conditions.”
• Environmental epidemiology – The National Research Council Committee on Environmental Epidemiology observes that environmental epidemiology is “the study of the effect on human health of physical, biologic, and chemical factors in the external environment, broadly conceived. By examining specific populations or communities exposed to different ambient environments, it seeks to clarify the relationship between physical, biologic or chemical factors and human health.”
• Occupational epidemiology – The Occupational Safety and Health Administration (OSHA®) states that occupational epidemiology “involves the application of epidemiologic methods to populations of workers. Occupational epidemiologic studies may involve looking at workers exposed to a variety of chemical, biological or physical (e.g., noise, heat, radiation) agents to determine if the exposures result in the risk of adverse health outcomes.”

The Impact of Epidemiology on Public Health

Public health focuses on implementing policies and programs to improve community health, while epidemiology studies disease patterns and causes to inform those public health efforts.  Epidemiology provides the data necessary for effective public health action.

Epidemiology helps answer what is happening, why it may be happening, and how sure we are regarding information about a disease or disorder. Public health practice focuses on what to do about it, with whom, and how to evaluate its effectiveness.

Natural Disasters and Epidemiologists

Every part of the world is at risk for some type of natural disaster, such as:

• Hurricanes
• Tornadoes
• Floods
• Winter storms
• Volcanic eruptions
• Wildfires

Often, you think of emergency management and disaster response as the primary defense in these situations. However, epidemiologists are critical in disaster response.

Natural disasters can impact a community’s infrastructure, which in turn increases the risk factors associated with disease outbreaks and illnesses. For example, contaminated water is a common post-disaster risk, especially if water pipes are damaged or water sources are contaminated due to floods.

Epidemiologists provide a continuous public health service in identifying and monitoring the health problems of the affected communities. Epidemiologists and public health professionals will assist with community health issues that arise during a natural disaster and recovery.

For instance, there was an earthquake in Haiti in 2010. The earthquake damaged infrastructure and contributed to contaminated water supplies, leading to a cholera outbreak.

The Centers for Disease Control and Prevention worked with the Haitian Ministry of Public Health and Population to respond to the disease outbreak. According to the CDC, “among those involved in the response were medical officers, epidemiologists, laboratory scientists, environmental health specialists, communication specialists, public health advisors, planners, information technology specialists, and support staff.”

Infectious Diseases and Epidemiology

Infectious diseases and vaccination programs are the most popular items people consider when thinking about public health. Epidemiology offers a greater understanding of infectious diseases and how to prevent them.

Epidemiologists analyze disease patterns, investigate disease outbreaks, and influence public health policies. Every time there is an emerging disease, epidemiologists are on the frontlines in public health surveillance. They determine how government agencies, health departments, and international organizations should respond to an outbreak or a pandemic, based on their discoveries of risk factors and health behaviors.

During the initial outbreak of HIV/AIDS in the early 1980s, for instance, epidemiologists revealed how the virus was transmitted and who was at increased risk. The movie, “And the Band Played On,” captures the efforts of epidemiologist Dr. Don Francis in the early response to HIV/AIDS.

This movie is a fascinating look at the public health practices of epidemiology in earlier decades. It also inspired my own personal public health career and early work in HIV prevention.

Environmental Health and Public Health

Environmental health is a branch of public health focused on how physical, chemical, and biological factors in the environment – air, water, soil, and food – impact human health. Major events – whether human-made industrial accidents or catastrophic natural disasters – are primarily responsible for the most extreme, large-scale environmental exposures in history.

In March 1979, for example, there was a partial meltdown involving the Three Mile Island nuclear facility near Middletown, Pennsylvania. Health officials eventually determined that this event did not cause a major impact to the population’s health, but both epidemiologists and environmental health specialists were involved in this outcome.

Community Health and Public Health Practice

Community health is an overarching term that can include multiple core areas of public health. For example, infectious diseases, environmental health, and natural disasters can all impact a community’s health. However, community health is related to a specified geographic location or demographic.

Vaccine-preventable diseases are considered one of the 10 Great Public Health Achievements, according to the CDC. The eradication of smallpox is one of the most notable vaccine-preventable diseases in public health.

The CDC notes that the World Health Organization started a plan to rid the world of smallpox in 1959. The beginning stages of the campaign were slow due to funding and other factors, but eventually the eradication efforts succeeded. The last known person to naturally acquire smallpox was identified in 1975.

Mental Health and Epidemiology

Mental health and psychiatric healthcare are often not considered when people think about epidemiology’s role in public health. But epidemiologists serve an important role because they look beyond individual patients.

Mental health involves many individualized and personal perspectives for mental health counseling and treatment. But epidemiologists look at entire communities to detect risk factors or the influence of health conditions such as genetics and substance abuse. The epidemiological research in these populations can help establish more mental health programs and healthcare services.

For instance, a Journal of the American Academy of Child and Adolescent Psychiatry® article explains how epidemiology can improve mental health services for children and adolescents. According to this article, “Epidemiology can help to improve mental health services for children and adolescents by increasing understanding of the causes, development, and course of psychiatric disorders. For the purpose of service delivery, epidemiologic research on child psychopathology can provide information on need for services, availability of services, and effectiveness of services.”

What Does an Epidemiologist Do?

According to Cleveland Clinic®, epidemiologists are public health professionals who study the patterns and disease among specific groups of people within society. Their work includes:

• Contact tracing
• Epidemiological research
• Disease pattern analysis

Contact Tracing

Epidemiologists commonly serve as contact tracers. According to the CDC, contact tracing is “the identification, monitoring, and support of the individuals (contacts) who have been exposed to the patient and possibly infected themselves.”

Epidemiological Research

Epidemiological methods include public health surveillance and descriptive studies to study distribution, and analytical studies to study the determinants of health-related events. Epidemiologists utilize various data collection methods, including taking blood samples, interviews, and surveys. Their data analysis helps them understand the causes and factors of specific health conditions and why diseases occur in certain areas.

Disease Pattern Analysis

Epidemiologists use scientific methods to answer questions about a communicable disease: who, what, when, where, how much, and among whom? Epidemiologists can be referred to as the informal “disease detectives.” While analyzing data, they search for “Patient Zero” – the first human infected by a disease in a new outbreak – and everywhere a disease has been or where it might go.

 Using various analytic tools, epidemiologists can identify risk factors or health trends that may impact population health. Ultimately, their data analyses assist public health officials and healthcare providers with preventive measures, outreach efforts, and health outcomes.

How to Become an Epidemiologist

Typically, an advanced degree, such as a Master of Public Health (MPH) with a focus on epidemiology, is required for most roles held by working professionals in epidemiology. In such a degree, biostatistics, infectious disease, and molecular epidemiology are typically emphasized. Epidemiology students learn to design studies, conduct disease surveillance, and analyze disease patterns within populations, which requires proficiency in statistical software and critical analysis.

How Epidemiology and Public Health Improve Health Outcomes

Combining scientific research with promoting health policy initiatives has significantly increased life expectancy. For example, national health initiatives have been shown to increase life expectancy through public health education and other work.

Epidemiologists are essential to public health services by tracing disease spread and predicting future trends. Together, public health and epidemiology are improving health outcomes for communities worldwide.

The Master in Public Health at APU

For adult learners interested in seeking public health roles or epidemiology roles, American Public University (APU) offers an online Master of Public Health. For this degree program, students can take courses in epidemiology, public health in America, and health policy. Other courses include the social and behavioral aspects of health, public health program planning and evaluation, and ethical issues in public health.

This MPH has also earned specialty accreditation from Council on Education for Public Health® (CEPH®). (Note: Please check APUS’s accreditation page for details on the current accreditation status.) This accreditation ensures that the program has been examined for high academic quality by professional examiners.

For more information, visit APU’s nursing and health sciences degree program page.

Note: This program has specific admission requirements.
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