What is epidemiology in public health?

As a branch of medical science, epidemiology is the study of populations to better understand the clinical causes and social influences of diseases and health outcomes within communities. This area of study is often associated with diseases, but it also deals with lifestyle and other health factors. For example, if a large percentage of the population experiences breathing problems, those who practice epidemiology might examine whether there is a causal relationship between shortness of breath and pollution levels.

Those who practice epidemiology may also work to identify new patterns and habits that can impact public health. And this is just the beginning. We spoke with Bob Vella, core faculty member in the University of Phoenix College of Health Professions and chief of the Communicable Disease Bureau, Delaware Division of Public Health, to discuss the pivotal role epidemiology plays in public health. 

In 1854, a cholera epidemic was ravaging the city of London. At the time, most doctors believed this illness was airborne, but physician John Snow had another theory. He tracked the cases of cholera throughout the city and identified a single water pump that he believed contained the source of the outbreak. To this day, Snow is considered a pioneer in epidemiology because of his then-novel approach to understanding the origins of an outbreak by studying who was affected.

Snow wasn’t the first person to study epidemics or analyze infectious diseases on a grand scale. Known as the founding father of vital statistics, John Graunt was an English draper who tracked birth and death rates in London and the countryside in the late 1600s. He observed that the urban death rate was higher than the rural rate and that males had higher mortality. He also created a table predicting life span and was able to quantify high infant mortality. Edward Jenner, an English physician, worked to develop a vaccine for smallpox in the 18th century. And there were others. In fact, the roots of epidemiology can be traced all the way back to the father of all medicine, Hippocrates.

Modern epidemiology uses a combination of statistics, social research and other skills to identify risk factors and determine the root causes of health problems within communities. 

Those who practice epidemiology might contribute to public health by working in a variety of fields and specializing in certain issues in medicine. There was a time, for example, when smoking was considered healthy and encouraged by doctors. Explorations in the field of epidemiology proved this wrong.

“Epidemiology plays a pivotal role in public health by providing the foundation for understanding, managing and improving the health of populations,” says Vella. “This was highly evident during the COVID-19 pandemic as frontline epidemiologists performed contact tracing, surveillance and monitoring, policy guidance and public health messaging. Their exhaustive work directly saved millions of lives globally.”

Some of the ways epidemiology contributes to public health are (followed by an example of each):

• Identifying environmental triggers and exposure to chemicals that cause illness (Flint, Michigan, water crisis)
• Tracking the spread and development of infectious diseases (COVID-19 pandemic)
• Developing policies to improve the health of communities (laws to require the use of seat belts)
• Promoting healthy habits in Americans to extend their life spans (recommendations for cardio and strength training exercises)

The field of epidemiology covers a mixture of community health and public health. Professionals can work in public policy or within a medical setting, depending on their passions. This field requires evidence-based practices to defend findings. Without countless studies spanning decades, anti-smoking legislation and seatbelt reform would not have likely occurred. 

Generally, three epidemiological techniques are used to examine disease. ”An epidemiologist might focus on one technique in their research or in the [2015 Zika virus] example below, use multiple options to identify the causes and risk factors associated with a disease,” Vella states.

This form of epidemiology addresses the who, what, when, where, why and how of a disease or condition. John Snow used this approach to see which members of London society were most at risk of contracting cholera. This epidemiological technique can identify patterns and key traits of a community to aid in disease prevention.  

Analytic epidemiology uses statistics to test hypotheses. John Graunt relied on this method to review birth and death certificates. The technique tries to use quantitative data to track patterns and potential issues. 

This form of epidemiology involves controlled experiments within labs. It tests new treatments and public health interventions before rolling them out to the general public. For example, research scientists at University of Houston worked to create a vaccine against fentanyl addiction. Controlled psychology experiments might also fall within this category.

Vella shares another example: “During the Zika virus outbreak in 2015, epidemiologists quickly established a case definition, collected patient data and mapped the spread (descriptive). They conducted a host of studies (i.e., case control) to identify key risk factors and monitored the disease progression (analytic). Finally, epidemiologists conducted vector control interventions (i.e., studies to evaluate the effectiveness of control measures like insecticides and larvicides). This is considered experimental epidemiology.”

Here are a few key concepts within the field epidemiology:

• Population at risk: The group of people most affected by a condition or problem. (One example is women who used contaminated baby powder and were at greater risk for cancer.) 
• Incidence: The number of new occurrences of an event within a certain time frame.
• Prevalence: The total number of cases within a population.
• Risk factors: Traits or behaviors that increase the chances of catching a disease.
• Outcomes: The results of changes in behavior or efforts to address the public health issue. (COVID-19 lockdowns were a public health measure to prevent the spread of the disease.)

Those terms often come up as those who practice epidemiology navigate the scientific method to develop theories and find the source of an illness or issue. They also test different solutions to public health problems to see how communities react to them.  

Epidemiology is an interesting field in medicine right now because of advancements in technology that contribute to research techniques. Historically, researchers have had to scour piles of health records and manually report data. Today, machine-learning tools look for patterns and highlight trends for research.

Vella adds: “Today, disease data is reported to all public health departments electronically. This provides epidemiologists with the ability to monitor for potential outbreaks in real time, utilizing geographic information systems (GIS). Early detection and a rapid response are instrumental to controlling infectious disease threats.”

Traditional research methods, however, still have a key role in epidemiology. They might run studies in which they track patient behavior or conduct interviews with members of the public. The human element is important in this field.

Those who practice epidemiology use a mixture of quantitative insight and qualitative analysis to develop the best possible methods to prevent illness and disease. 

As you explore the field of epidemiology, you may notice that data collection, analysis and integrity play a major role. Just as John Snow needed data to prove that cholera came from a contaminated well, modern epidemiologists need accurate data to advocate for public health change. Statistics and data management skills are especially important in this career path. 

As you explore a career in epidemiology, you can decide whether to pursue regional research or work to address global trends. Even if you take steps to help your neighborhood and local community, your insights could be used to develop programs across the country — or the globe. Here are just a few examples:

• Syringe services programs (SSPs) — Formerly known as needle-exchange programs, SSPs are a critical harm-reduction tool to decrease cases of HIV and hepatitis C, as the use of dirty needles can spread blood-borne pathogens.
• Events like World No Tobacco Day highlight global food insecurity and the dangers of smoking and chewing tobacco simultaneously. The day serves to encourage farmers to grow food as their main crop instead of the tobacco plant.
• Forest fires can spread smoke across multiple countries — like the ones that enveloped the U.S. East Coast from Canada. Those who practice epidemiology can track the short- and long-term effects of poor air quality on populations in affected areas. 

In each of those cases, those who work with epidemiology might respond to a local crisis but the research can be applied to communities across the world. 

Several job paths within public health have ties to epidemiology. Some individuals start in entry-level healthcare jobs, where they can further learn skills that can lay a solid foundation for a future in public health. Epidemiology has a role in jobs such as public health educator, public health officer, health education specialist and community health advisor.

For example, a health education specialist uses epidemiology to assess and analyze patterns of disease and health behaviors within populations. By understanding the prevalence and risk factors associated with various health issues, health education specialists can design targeted educational programs and interventions to promote healthier behaviors and prevent the spread of diseases within communities.

To become a health education specialist, typically you need a bachelor’s degree in a related field. Some organizations seek individuals with a master’s or doctoral degree. In this role, important skills include how to access health needs of a community or population and then collecting and analyzing data to best service the community.

After obtaining a bachelor's degree in a health-related field, aspiring individuals interested in leadership roles within public health or furthering their knowledge in the field may choose to pursue a Master of Public Health with a concentration in Community Health Leadership. 

If you’re interested in public health and stepping into leadership roles, University of Phoenix (UOPX) offers a Master of Public Health with a concentration in Community Health Leadership.

In this program, you’ll learn about epidemiology in the MPH/530 Epidemiology Concepts and Public Health Diseases. The course provides an introduction to skills public health professionals need to critically interpret disease. The main concepts cover distributions and determinants of disease, disability, injury and death in human populations. Students have an opportunity to apply epidemiology concepts to case studies.

Students enjoy a flexible schedule while also learning about the following:

• Assessing community health needs to develop and interpret public health programs
• Creating and implementing community health programs
• Evaluating and applying principles of biostatistics, environmental health, epidemiology and social-behavioral models
• Evaluating programs and appropriately applying public health research findings to community health initiatives
• Advocating for improved health outcomes, communicating a shared vision, influencing change and championing solutions
• Evaluating current local and global health trends and creating recommendations for institutional and health policy response
• Mobilizing community stakeholders for public health initiatives in diverse settings
• Creating and marketing health communications for individuals and groups from diverse cultural, ethnic and educational backgrounds
• Creating an effective leadership strategy, leading public health professionals and managing multidisciplinary system stakeholders

Graduates of this program will be better prepared for leadership roles in health education and community health settings.