What is Descriptive Epidemiology and How is it Applied?

A thorough understanding of disease patterns is the key to protecting public health. This was famously demonstrated in one of the earliest examples of what would become the science of epidemiology: Dr. John Snow's analysis of a cholera outbreak in London in 1854.¹

Dr. Snow mapped confirmed cholera cases and paired that information with his own conviction that cholera was a water-borne disease. He identified a city water pump as the most likely source of contaminated water. After he persuaded the authorities to disable the pump, the epidemic subsided. This was an important breakthrough in understanding how cholera was spread, and arguably an even more significant development in demonstrating the ways in which public health is improved through methodical understanding of disease patterns.

The science Snow pioneered continues to shape public health today, and the professionals who master it are among the most influential voices in medicine. This blog takes a closer look at descriptive epidemiology and its essential role in protecting and improving public health.

What is Descriptive Epidemiology?

Epidemiology is the study of why and how often diseases occur within specific groups of people.² Broadly, there are two branches of epidemiology: descriptive and analytic.³ Descriptive epidemiology is principally concerned with describing what happened. A typical descriptive epidemiology study will pull together the "what," "who" and "where"—known as the components of the epidemiological triangle—to show how a disease outbreak has affected a particular population. The results of that study can then be used to formulate a hypothesis about why the outbreak happened, and analytic epidemiology is the process of testing that hypothesis.

The Snow example illustrates the relationship neatly: Mapping the cases and their location was the descriptive work; testing the hypothesis by disabling the pump was the analytic epidemiology.

How a Descriptive Epidemiology Study is Designed

What is descriptive epidemiology? In its purest form, it is the description of the distribution of a disease within a population.³ Descriptive epidemiology does not seek to explain why an outbreak has occurred, but it is an important part of the information that ultimately provides evidence to address that question.

As such, the basic elements of a descriptive epidemiology study are focused largely on defining and describing the disease and its distribution within a population.

Key steps in the design of a descriptive epidemiology study:

1. Define the problem and study objectives: State the issue being studied and define the overall objective of the exercise. For example, "There is a cholera outbreak in London. The study will describe the distribution of cases in the outbreak across London."
2. Define the population: Who is being studied? "Confirmed cholera cases in London in 1854"
3. Define the case: In our example, this would establish the criteria for confirming a cholera diagnosis.
4. Describe the disease by:
   a) Time: Establish any time pattern for the outbreak; for example, there might be seasonal variation.
   b) Place: Establish physical location(s) of cases (which turned out to be key in the 1854 cholera outbreak)
   c) Person: Establish any potential common factors among patients, such as age, gender or occupation
5. Measure disease occurrence: Where is the disease occurring? Is there variation in symptoms or severity?
6. Formulate a hypothesis to explain the disease distribution. This helps to inform the analytic epidemiological methods that will be applied next. Those methods include:
   a) Identifying data sources and collecting data: Relevant data from appropriate sources provide the foundation for testing the hypothesis.
   b) Analyzing and interpreting data: These are the defining elements of analytic epidemiology.
   c) Reporting and disseminating findings: This is critical to informing public health strategy and tactics.

Real-World Applications of Descriptive Epidemiology

Descriptive epidemiology is an essential technique for the management of public health.

In 2024, for example, US public health officials used descriptive epidemiology methods to track the spread of avian flu in herds of dairy cattle and identify the subsequent emergence of avian flu cases in humans who had worked with infected cows.⁴

The United States Centers for Disease Control and Prevention (CDC) continue to use descriptive epidemiology studies to monitor COVID-19 cases, helping to inform public health guidance regarding vulnerable segments of the population, such as asthmatics or people undergoing dialysis.⁵

Investigators working for the Division of Cancer Epidemiology & Genetics at the National Cancer Institute developed a COVID-19 mortality tracker using descriptive epidemiology techniques that monitor cancer distribution in the USA.⁶

Ultimately, descriptive epidemiology is a powerful tool—one with applications spanning infectious disease, chronic illness, cancer research and beyond. For public health professionals looking to deepen that expertise, Kent State University's online Master of Science in Clinical Epidemiology provides the rigorous, research-focused training to put it to work at the highest level.

Turn Your Expertise Into Impact

Descriptive epidemiology is the foundation of sound public health policy: the disciplined process of establishing what is happening, and to whom, so that public health professionals can ask the right questions and design the right interventions.

If you're ready to deepen that expertise and take on a more rewarding role in public health, Kent State University's online Master of Science in Clinical Epidemiology is designed for professionals like you. The program is STEM-designated and accredited by both the Council on Education for Public Health (CEPH) and the Association of Schools and Programs of Public Health (ASPPH)—markers of quality that carry real weight with employers. The curriculum builds sophisticated competency in research methods, biostatistics and study design, with electives that let you tailor your degree to your professional goals.

You'll learn from faculty who are active researchers and recognized leaders in their fields—scientists whose work is funded by institutions including the National Institutes of Health, the Robert Wood Johnson Foundation and the Centers for Disease Control and Prevention. In small online classes, they bring that frontline expertise directly to you, wherever you are and on a schedule that fits your professional life. You'll also build a network of peers and practitioners who can open doors throughout your career.

Epidemiologists are in high demand: the U.S. Bureau of Labor Statistics projects 16% job growth for epidemiologists between 2024 and 2034—much faster than the national average.⁷ Graduates of the program go on to careers as research scientists, clinical trial managers, data scientists and more, in settings ranging from public health agencies to research institutions to the private sector.

Explore the online MS in Clinical Epidemiology at Kent State, including curriculum details and admissions requirements. Then schedule a call with an admissions outreach advisor, who will help you map out your next steps.