What is Epidemiology?

Epidemiology, as a basic public health science, involves studying the health of populations as a way to gain insight into the causes and patterns of disease within these populations.

Epidemiology is often said to be instilled with the spirit of using epidemiologic information to promote and protect the public’s health.

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Epidemiology (which roughly translates to “the study of people” in Greek) is a number of things:

  • Epidemiology is a quantitative discipline based on statistics, probability, and sound research methods.
  • Epidemiology is a method of reasoning based on developing and testing hypotheses related to health and illness.
  • Epidemiology is a public health tool used for promoting and protecting the public’s health.


Epidemiology and Public Health

Epidemiology involves studying the distribution and determinants of disease frequency in specific populations and applying the findings to control health problems. Epidemiology is therefore often used to search for causes and other factors that influence the presence, occurrence, and recurrence of health-related events, such as injuries, diseases, and conditions.

For example, public health professionals working in epidemiology often compare groups of people with differing rates of disease occurrence and work to understand why these variations exist by studying:

  • Their demographic characteristics
  • Their genetic or immunologic makeup
  • Their behaviors
  • Environmental exposures
  • Other related risk factors or potential risk factors

The work of these specialists, under ideal circumstances, is designed to initiate swift and effective public health control and prevention measures.

Originally, epidemiology in the realm of public health was focused purely on epidemics of communicable diseases and then to endemic communicable diseases and non-communicable infectious diseases. However, contemporary epidemiology now extends far beyond these areas of study to include:

  • Behaviors related to health and well-being (e.g., exercise, seat belt use, etc.)
  • Birth defects
  • Chronic diseases
  • Environmental health
  • Injuries
  • Maternal and child health
  • Occupational health


Epidemiology: Identifying Populations and Directing Public Health Action

Epidemiologists, like clinicians, are concerned with disease and the control of disease. However, unlike clinicians who are concerned with the health of the individual, epidemiologists are concerned with the collective health of a community. And unlike clinicians who focus on treating and caring for the individual patient, epidemiologists focus their work on a number of factors related to illnesses, such as the source of the illness (or the action that caused it), others who may have been exposed to it, and methods to prevent additional cases or recurrences.

However, it is important to realize that epidemiology involves more than the study of illness within a population. As a discipline within public health, epidemiology produces research and data that is then used for directing public health action. It is the responsibility of epidemiologists and similar professionals to utilize scientific methods of descriptive and analytic epidemiology to study and come to conclusions about the health of a community. Their work also involves a great deal of planning regarding how to control and prevent disease in the community.

Epidemiology directs public health action by:

  • Providing Community Health Assessment: In order to set policy and plan programs, public health officials must be able to assess the health of the populations they serve and determine whether health services are accessible, efficient, and effective, and available.
  • Influencing Individual Decisions: Public health officials provide information on making better decisions that affect health (e.g., making better food choices, taking the stairs instead of the elevator, etc.). Countless epidemiologic findings are directly relevant to the choices we make every day, with many of these choices often affecting our health over a lifetime.
  • Completing the Clinical Picture: Epidemiologists have long contributed to physicians’ understanding the clinical picture and the natural history of diseases.
  • Searching for Causes: Much of epidemiologic research is devoted to searching for causes or factors that influence the risk of disease among populations. Epidemiology often provides enough information to support effective public health action.


Careers in Epidemiology and Research

Epidemiology is a broad field of study within public health that involves the expertise of a number of researchers and specialists, such as:


Epidemiologists, also known as medical scientists, examine the causes of diseases as to prevent them from returning or recurring. These professionals, who may work for hospitals, health departments, laboratories, universities, pharmaceutical companies, or health insurers, among others, are responsible for tracking infections, reading and analyzing data, and assessing where interventions may be necessary.

Epidemiologists are also responsible for reporting their findings to public policy officials and to the general public, and they are often called upon to complete fieldwork, conduct interviews, and collect samples for analysis.

Their work also involves managing public health programs through design and planning, by monitoring the progress of these programs, by analyzing data, and by seeking ways to improve public health programs.

Epidemiologists may be research epidemiologists, who often work for universities, or applied epidemiologists, who most often work for governments, where they are called upon to directly address and examine health crises. It is common for epidemiologists to focus their careers on specific areas of study, such as:

  • Bioterrorism/emergency response
  • Chronic diseases
  • Infectious diseases
  • Injury
  • Maternal and child health
  • Occupational health
  • Substance abuse

Vaccine Researchers

Vaccine researchers are scientists who conduct research that facilitates the development of effective vaccines for human disease. These professionals typically work for universities, private laboratories, government agencies, and not-for-profit laboratories.

Most of the time, the work of vaccine researchers is funded through federal grants from agencies such as the CDC, the National Institutes of Health, and the National Institutes of Allergy and Infectious Diseases. Private industry, which includes contract labs and pharmaceutical and biotech companies, among others, may rely on private funding or revenue resulting from successful commercial products.

Not-for-profit vaccine development is often conducted by organizations such as the Global Alliance for Vaccines and Immunization and the World Health Organization.

Disease Ecologists

Disease ecologists study the interactions between pathogens and parasites and their human or non-human hosts. Because the outbreak of infections is often caused by changes to the ecology of the host, the environment, or the pathogens, disease ecologists are called upon to understand the ecology of the interaction and the prevalence, incidence, or timing of diseases.

Disease ecologists are researchers who must draw on their knowledge of genetics, molecular biology, genomics, immunology, epidemiology, and spatial modeling to investigate parasites and pathogens in the environment. These scientists work to understand pathogen transmission and how it impacts host populations.

Degrees in Epidemiology and Research

Public health scientists in epidemiology and research most often pursue their undergraduate degrees in areas such as chemistry, cellular or molecular biology, microbiology, and biochemistry.


Given the highly technical and interdisciplinary field of epidemiology, most of these professionals pursue masters and even doctoral degrees. One of the most widely pursued master’s degrees for scientists in the public health field is the Master of Public Health (MPH).

The MPH, in addition to providing a broad background in all of the core areas of public health, allows students to focus their graduate work on a specific area of study, such as epidemiology and research. Therefore, an MPH in Epidemiology is designed for individuals who want to conduct research into the causes, prevention, and control of human disease.

The curriculum of an MPH in Epidemiology is focused on the mastery of methods of epidemiologic research and is typically enriched with a curriculum of a number of important disease outcomes, such as AIDS, cancer, and tuberculosis, as well as factors that are often important in disease causation, such as genetics, nutrition, and the environment.

Some of the coursework unique to an MPH in Epidemiology includes:

  • Introduction to biostatistics
  • Epidemiologic methods
  • Field studies in epidemiology
  • Principles of infectious disease epidemiology

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