What Is Epidemiology? Definition, Types, and Careers

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A team of epidemiologists studies the spread of a contagion on an electronic map.

When there is an outbreak of disease or a pandemic, millions of people suddenly face serious questions: Who is responsible for finding its source and determining how it is spreading? Who is in charge of ascertaining where the disease will spread next and informing the public?

Whenever large-scale health issues or diseases occur, health experts known as epidemiologists track the source, determine who has been affected, and study its modes of transmission. Who are epidemiologists and what is epidemiology? According to the Centers for Disease Control and Prevention (CDC), “Epidemiology is the method used to find the causes of health outcomes and diseases in populations.” The study of epidemiology enables professionals to use data to identify the source — as well as track the spread of — health-related issues and events.

The principles of epidemiology are used to describe the conditions of diseases, injuries, and environmental hazards. They can also be used to help control the spread of diseases. Epidemiologic concepts are applied to populations of varying types, viewing individuals as part of the collective whole of society.

Why Is Epidemiology Important?

Epidemiology has a significant impact on the field of health care, as well as health information management and community health. According to the American Health Information Management Association, “Health information management (HIM) is the practice of acquiring, analyzing, and protecting digital and traditional medical information vital to providing quality patient care.” The study of epidemiology considers the whole of society as its patient. It seeks to acquire and analyze important health information to ensure the well-being of members of all communities.

What Are the Categories of Epidemiology?

A key category of epidemiology focuses on infectious diseases. Epidemiologists determine why infectious diseases such as pneumonia spread to certain populations and measure how quickly they spread. Other infectious diseases can include influenza and foodborne illness.

Epidemiologists not only study the source and spread of infectious diseases but other health problems and events as well. These may include the following.

  • Non-infectious diseases such as the rise of a certain type of cancer, or an increase in heart disease, diabetes, or lung disease. While these cannot be spread from one person to another like a virus, epidemiologists study communities for widespread or localized cases of non-infectious diseases.
  • Environmental exposures to radioactive materials, air pollutants, lead, asthma triggers, or other contaminants can negatively affect a population.
  • Injuries and violence in communities, such as domestic violence, suicide, or homicide. As patterns of injuries and violence change over time and from community to community, epidemiologists study ways to help control and minimize violence.
  • Terrorism and acts of extreme violence in specific communities as well as in society as a whole. For example, epidemiologists helped gather data during the 9/11 terrorist attacks on the World Trade Center and the Pentagon.
  • Natural disasters are analyzed that can have a catastrophic impact on the lives of people in diverse communities.

Measuring Health Issues and Informing the Public

The discipline of descriptive epidemiology seeks to measure different aspects of a public health issue. Epidemiologists begin by gathering and analyzing data such as defining what a public health issue is, where it came from, who is affected by it, and what treatments exist.

Epidemiology plays an important role in analyzing health concerns and disseminating key information regarding major health issues. For example, concerning the COVID-19 pandemic, epidemiologists have worked to inform the public about the following:

What Is COVID-19?

By defining a specific disease, epidemiologists can begin addressing the source of a public health issue. For instance, the World Health Organization (WHO) provides a definition of COVID-19. It writes that “Coronavirus disease (COVID-19) is an infectious disease caused by a newly discovered coronavirus. Most people infected with the COVID-19 virus will experience mild to moderate respiratory illness and recover without requiring special treatment.”

How Much Has COVID-19 Spread?

By keeping the public up to date on where, how quickly, and by what modes of transmission the disease is spreading, people can begin to take necessary precautions. Research has shown that with COVID-19, people can spread the disease even when they are asymptomatic (show no signs of symptoms or infection).

When Did COVID-19 Begin Spreading?

Providing a history of an infectious disease’s source point and its initial spread can help epidemiologists predict future spread. When medical professionals realized it took a short amount of time for COVID-19 to spread from Wuhan, China to all parts of the globe, they understood they were facing a pandemic.

Where Did It Come From?

Epidemiology helps determine the source of a public health issue and can usually help implement preventive measures. With COVID-19, it is a form of coronavirus that medical experts have never seen before. As a result, epidemiologists and public health experts had to research how it differed from other strains of coronavirus and where it originated.

Who Will It Affect the Most?

By identifying communities that are most impacted, epidemiologists can help inform different people about their potential risk.

  • Regarding COVID-19, the Centers for Disease Control and Prevention writes, “Based on what we know now, persons at higher risk for severe illness from COVID-19 are people 65 years and older, people who live in a nursing home or long-term care facility, and people of all ages with serious underlying medical conditions.”

Policies and Recommendations

Epidemiology not only addresses and measures multiple categories of health issues, but also establishes policies and recommendations for the public. This guidance can be crucial to help populations mitigate the dangers associated with a particular issue.

For instance, once epidemiologists and medical experts understood that COVID-19 could be spread through water droplets, a recommendation was made for people to wear masks. Soon after, policies were put in place that required people in some parts of the U.S. to wear masks to prevent further spread of the disease.

What Is Social Epidemiology?

Those who want to better understand what epidemiology is and how it directly impacts lives should explore social epidemiology. Social epidemiology seeks to assess how social structures, living conditions, socioeconomics, and other factors affect public health. These epidemiologists then create policies that can promote better and healthier living conditions.

Social Epidemiology Defined

The Environmental Health and Preventive Medicine journal writes, “Social epidemiology is a branch of epidemiology that focuses particularly on the effects of social-structural factors on states of health. [It]  assumes that the distribution of advantages and disadvantages in a society reflects the distribution of health and disease.” Social epidemiology is important as it seeks to understand the health issues of specific communities and populations, and how governments and non-governmental organizations can address inequalities.

Health Concerns in Social Epidemiology

Social epidemiology focuses on how health-related concerns impact various aspects of society. There are various structural, relational, cultural, and economic components that comprise a social epidemiology study. Often, social epidemiologists will study social relationships and social inequalities related to:

  • Age, sex, race, or ethnicity of individuals living in low socioeconomic areas
  • Poor diet
  • Communities living in disadvantaged neighborhoods
  • Poor exercise habits
  • Likelihood of developing a smoking habit or alcohol addiction
  • Accessibility to health care

Public Education and Policies

Social epidemiology also has an important impact on population health and public education. Epidemiologists work alongside a wide variety of professionals, such as those in government, health care, psychology, and sociology. These different fields seek to better understand human behavior and living conditions, as well as address health concerns and improve medical outcomes.

Public education is a core element of what epidemiology is. Health educators, community health workers, and public health officials introduce epidemiological research and information to communities and populations.

  • Health educators can teach a specific community about a particular health issue that affects them, such as the disadvantages of poor exercise and eating habits.
  • Community health workers may serve as the bridge between community members and public health officials. They may also strategize how policies can improve the health and living conditions of individuals.
  • Public health officials, whether in local, state, or federal government, write and establish policies that promote health and wellness in the communities and populations they serve.

Genetic Epidemiology Defined

When defining epidemiology and understanding how it benefits communities and individuals, it is important to consider genetic epidemiology. Genetics can play a significant role in the effects of diseases, whether infectious or noninfectious. With a firm grasp of genetics, epidemiologists and medical experts can better understand health problems and how they spread.

What Is Genetic Epidemiology?

According to the National Human Genome Research Institute, “Genetic epidemiology is a relatively new medical discipline that seeks to understand how genetic factors interact with the environment in the context of disease in populations. Areas of study include the causes of inherited disease and its distribution and control.” Genetic epidemiology contributes to our understanding of how, when, why, where, and to what extent some people have natural tendencies toward health issues.

Non-communicable Diseases

Genetic epidemiology focuses on understanding the genetic factors that can influence the health of populations, as well as how these factors can correlate to certain environmental elements. According to the World Health Organization, professional epidemiologists often study and analyze the following non-infectious, or non-communicable, diseases:

  • Cancer: lung, breast, stomach, colon, and liver
  • Diabetes: Type 1 and Type 2
  • Heart diseases: heart failure, coronary heart disease, cerebrovascular disease, rheumatic heart disease, and congenital heart disease
  • Asthma

These diseases can be chronic at all stages of life. Often, they are fatal. Epidemiology helps health experts determine which communities or individuals may be predisposed toward these non-communicable diseases. For instance, some individuals can be born with altered genes that make them more likely to develop cancer.

Environmental Epidemiology Explained

There are many environmentally driven physical, chemical, and biological factors that can impact the health of a specific population. While genetics can play a significant part in an individual’s risk of acquiring non-communicable diseases, the following factors can contribute to whether some individuals may be more susceptible than others:

  • Unhealthy eating habits
  • Tobacco and smoking
  • High alcohol consumption
  • Lack of exercise
  • Hypertension
  • Exposure to environmental carcinogens and pollution
  • Viral infections

An individual’s age and lifestyle may influence the effect of an environmental factor. For instance, elderly individuals may be more prone than children to develop heart diseases, due to lifelong habits as well as the condition of the environment around them.

Environmental epidemiology seeks to understand how environmental aspects, as well as community infrastructure or industry, can impact a population’s health.

Vulnerable Communities

Just as some individuals are more susceptible to non-communicable diseases due to their genetic makeup, some communities are more susceptible to health problems due to their physical environment.

One of the most vulnerable populations in the U.S. are the homeless. With no permanent shelter, access to regular medical care or healthy foods, people who are homeless can quickly catch viral diseases and develop unhealthy lifestyles.

Other populations that regularly face health problems are those that are socioeconomically disadvantaged. Individuals living at or below the poverty line may not have equal access to necessary medical care. They may not understand their medical conditions or be able to receive the medication or treatment necessary for recovery.

Etiology vs. Epidemiology: What’s the Difference?

People wondering, “what is epidemiology?” often also ask, “what is etiology?” Although they are different terms, many people use them interchangeably.

Etiology is the study of the cause of diseases. Epidemiology can be seen as an extension of etiology, as it seeks to understand the cause and spread of diseases or health problems in certain populations or across society as a whole.

At its core, etiology focuses on how diseases relate to one another as well as discovering their origins. Etiology relies on historic and scientific data to better understand diseases, while epidemiology relies on collecting data to conduct new research on emerging diseases.

Etiology and Epidemiology Working Together

Epidemiology is an ongoing process that uses the scientific method and can be applied to the study of current diseases and how they can be cured in the future. While etiology can be applied to the study of diseases, it also has a role beyond the medical field, connecting with other fields of study.

Etiology’s primary role consists of pinpointing the cause of a particular health issue, while epidemiology focuses on the factors concerning the spread and containment of health issues. The two can be used in combination to form a comprehensive health strategy.

Careers in Epidemiology

The study of epidemiology can lead to a variety of careers in public health.

Health Services Manager

Health services managers primarily work in hospitals to improve medical outcomes at their facilities. They have more administrative duties than research responsibilities, ensuring that facilities implement policies and regulations mandated by health care organizations and public health officials.

On a day-to-day basis, medical and health services managers communicate with staff members, create their schedules, oversee department budgets and finances, manage patient billing, and assume other key duties. According to the U.S. Bureau of Labor Statistics (BLS), medical and health services managers earned an annual median salary of $100,980 in 2019.

Health Information Manager

The work of health information managers is data driven, combining business and technology in health care. Health information managers are integral in the process of recording patient data and overseeing how electronic health records store medical information. They are in charge of collecting and analyzing patient data to help provide more effective and efficient patient care.

Health information managers make an annual median salary of approximately $57,000, according to May 2020 data from the website PayScale.

Community Health Educator

Individuals who are interested in how epidemiology directly impacts communities may consider a career as a community health educator. These professionals work in government organizations, local medical facilities, civic centers, religious organizations, family services agencies, or outpatient care centers. Community health educators study their population’s health needs, and provide educational sessions or training to disseminate information and improve outcomes.

Community health educators also serve as advocates for communities by discussing policies and programs with public officials that can promote health education and medical wellness. The job outlook for community health educators is projected to grow 11% between 2018 and 2028, and the annual median salary was $46,910 in 2019, according to the BLS.

Make a Vital Difference in Society

Those who understand what epidemiology is appreciate its role in preserving global health and mitigating the damage of widespread health issues during times of crisis. Whether studying social, genetic, or environmental issues related to diseases or public health, epidemiologists do important, meaningful work.

Individuals with a background in health care or public health can further develop the knowledge and skills to be effective in an epidemiology-related role.

Students may consider pursuing Ohio University’s online Master of Health Administration program. The robust curriculum includes courses such as Health Policy, Epidemiology in Health Administration, and Leadership of Health Organizations.

Learn more about how Ohio University can help you embark on a rewarding public health career today.

Recommended Reading:

Health Care Administration vs. Health Care Management: What’s the Difference?

The Characteristics That Make a Great Leader in Health Administration

The Major Problems in the U.S. Healthcare System and How They May Be Fixed


American Health Information Management Association, HIM Careers — What Is Health Information
Centers for Disease Control and Prevention, Describing Epidemiologic Data
Centers for Disease Control and Prevention, What Is Epidemiology?
Healio, Expert Strategy Identifies Etiology in Indeterminate Acute Liver Failure Cases
The Lancet, Embracing Complexity in Social Epidemiology
National Health Care for the Homeless Council, Integrating Community Health Workers into Primary Care Practice
National Human Genome Research Institute, Genetic Epidemiology
Nature, Epidemiology is a Science of High Importance
PayScale, Average Health Information Manager (HIM) Salary
STAT, Coronavirus
STAT, WHO Declares the Coronavirus Outbreak a Pandemic
U.S. Bureau of Labor Statistics, Health Educators and Community Health Workers
U.S. Bureau of Labor Statistics, Medical and Health Services Manager
Vox, How Canceled Events and Self-Quarantines Save Lives, in One Chart
World Health Organization, Coronavirus
World Health Organization, Situation Report 54