Education, Epidemiology

What is Epidemiology?

Author Kimberly Hazel , 10-May-2022

It’s impossible to live in the modern world without having some exposure to the dangers and possible effects of infectious diseases. These afflictions have plagued humanity since the dawn of civilization and before. From the bubonic plague (also known as the “Black Death”) that caused the deaths of millions of Europeans in the middle ages to common modern-day ailments like chickenpox, infectious diseases have always been a part of human life.


While these diseases carry varying mortality rates, their impact on how we interact with each other and the world around us is undeniable, and epidemiology is key in detecting the spread of infectious diseases.


Thanks to epidemiology, we understand what causes infectious diseases, how they spread, and how to treat them more than ever before. Despite this, modern science must remain constantly vigilant in understanding infectious diseases to prevent small outbreaks from becoming large-scale epidemics.

What Is Epidemiology?


Epidemiology is the scientific study of the determinants and distribution of health-related states or events in clearly defined populations and the application of this study to the control of health problems. Put simply, epidemiology is the study of what causes diseases, how they spread, and how to use that information to minimize the effect and spread of infectious diseases on populations. Epidemiology is a more focused field of study under the umbrella field of microbiology.


What Are Determinants?


One key factor of epidemiology is the search for and identification of determinants. Determinants can be defined as any cause or factor that influences the occurrence of an infectious disease or any other public health-related event. Epidemiologists work under the assumption that illnesses do not occur randomly in a population but only occur when the proper combination of risk factors exists in an individual.


What Is Distribution?


Distribution in epidemiology is concerned with two key factors: frequency and pattern. Frequency refers to very specific numbers of illnesses or health events. For example, the number of individual cases of COVID-19 in a defined population. Frequency also refers to the relationship of the number of individual cases relative to the size of the population.

Pattern refers to the occurrence of health-related events and illnesses by time, place, and person. Time patterns may be annual, seasonal, weekly, daily, hourly, or any other specific breakdown of time that can potentially influence disease or injury occurrence.

Place patterns include geographic locations and variations, rural and urban differences, and locations of specific work sites or schools

Why Is Epidemiology Important?


The importance of epidemiology has undoubtedly been at the forefront of international conversation in the past few years with the emergence of a pandemic with worldwide consequences. When an illness or disease occurs in a population or community, epidemiologists act as “disease detectives” to determine where a disease is coming from and which people that disease is most likely to impact.


The quicker epidemiologists can understand the disease, the more effectively they can minimize the spread and impact. Epidemiology is at the core of public health, and it informs policy decisions and evidence-based medicine by identifying potential risk factors for disease and targets for preventative medicine.

The History of Epidemiology

Origins in Greece


Hippocrates developed the root theories of epidemiology, a legendary Greek physician often considered the “Father of Medicine.” He’s believed to be the first person to examine the relationships between the occurrence of diseases and environmental influences. He was also the first to outline the difference between “endemic” and “epidemic” diseases. According to his findings, endemic diseases “reside within” a population while epidemic diseases are “visited upon” a population.

Birth of Epidemiology in Spain


While Hippocrates built the framework for what would become modern epidemiology, a Spanish physician named Joaquín de Villalba is believed to be the person who popularized the term “epidemiology,” referring to the study of epidemics. His 1802 book entitled Epidemiología Española contained a historical chronology of Spanish epidemics up to that point, taking note of the type of disease and the time and location in which the outbreak occurred.


The Discovery of Microbial Culprits


The very first scientist to introduce the idea that epidemics may be caused by invisible organisms being transferred from one subject to another was the Italian Girolamo Fracastro in the 16th century.

However, the existence of microorganisms was not confirmed until the 17th century, when two scientists from The Royal Society named Robert Hooke and Antoni van Leeuwenhoek found that there was more than meets the eye when it comes to specific biological processes.

The two scientists used the most rudimentary magnification devices that acted as the world’s first microscopes. While these devices could only magnify from 25-fold to around 250-fold, this was still enough to identify larger microbial organisms. In 1665, the duo would publish their research in a book entitled “Microphagia,” which presented the first published description of a microorganism, the microfungus Mucor.

The Father of (Modern) Epidemiology


English physician Dr. John Snow is given credit for kickstarting the modern age of epidemiology in the 19th Century. Between the years 1831 and 1854, tens of thousands of people in England died of cholera, a highly infectious disease that causes extreme diarrhea, vomiting, and dehydration.

Dr. Snow had spent time trying to convince his peers that the spread of cholera was mainly due to the consumption of contaminated water. Snow first published an article outlining his claims in 1849, but his contemporaries believed his theory to be false and instead bought into the popular theory that cholera was caused by breathing tainted vapors.

England in the mid-1800s wasn’t exactly what anyone could consider hygienic. There weren’t any modern toilets and running water in peoples’ homes, so leagues of citizens would get their drinking water from communal pumps and dispose of their human waste in pits known as “cesspools” or, worse, dump their waste directly into the Thames River. The river, of course, was the source of water that supplied communal drinking pumps.

A particularly bad outbreak of cholera occurred in Soho in 1854. Dr. Snow spent time documenting hundreds of disease cases and determined that the outbreak only affected those who drank water from one particular communal water source, the Broad Street Pump. Now, with evidence in hand, Dr. Snow was able to convince his peers of the waterborne nature of cholera.

Snow’s method of documentation and tracing of cholera back to that single pump laid the foundation for modern epidemiology and techniques that are still put into practice by the United States Center for Disease Control (CDC), the European Centre for Disease Prevention and Control (ECDC), and other various epidemiological institutions across the globe.

How Do I Become an Epidemiologist?


To pursue a career in epidemiology, you must first establish a knowledge base in organic chemistry and microbiology. Microbiologists are much sought after in the industry of epidemiology. The first step towards resolving issues caused by microorganisms is to understand what they are and how they operate fully.

Whether you’re starting your career in the United States, Europe, Asia, or other parts of the world, becoming a certified epidemiologist breaks down into five basic steps.

Earn a Bachelor’s Degree in a related field.


Most institutions for higher learning do not offer undergraduate programs specifically for epidemiology. Because of this, the first step on the track toward becoming an epidemiologist requires obtaining a degree in a related field of study. Some of the most popular undergraduate degree options for prospective epidemiologists include biostatistics, health science, nursing, biology, chemistry, and public health.


Gain real-world work experience.


Like many careers in public health, prospective epidemiologists are required to have some real-world experience in a medical or laboratory setting. Many of the most competitive master’s programs will require some form of work experience to set you apart from the crowd. At this stage, it’s essential to take time to determine the type of position you’re seeking before you search for relevant work experience to ensure that it aligns with your preferred career path in epidemiology.


Complete a Master’s Degree or higher.


Even most entry-level epidemiology careers require a master’s degree from an accredited institution. The majority of people in this stage will pursue a Master of Science or a Master of Public Health with a concentration in epidemiology. This is true for students in the United States, Canada, Europe, and China.

Ideally, these higher learning programs will contain community health, environmental health, biostatistics, and research methodology coursework. These areas will help prepare prospective epidemiologists for the data analysis and testing required in the industry.

Many master’s programs also require that students complete a research project to show that they can effectively put the skills they’ve learned in their coursework into practice.


Earn Certifications in Epidemiology


While there are no formally required exams to become an epidemiologist, there are various certifications that a person can pursue to legitimize their skillset in the eyes of potential employers. In the United States, the Certification Board of Infection Control and Epidemiology has a certification available for professionals.

In the United Kingdom, If you’ve earned a degree in life sciences (e.g., biomedical sciences, biology, microbiology, or biochemistry) and want to work in a clinical setting, you can apply for a place on the NHS Scientist Training Programme (STP) specializing in infection science.

To become an epidemiologist in China, students must first achieve a Master’s Degree in epidemiology. There are many opportunities for field study training programs to add further legitimacy to their skillset.

Start Your Career as an Epidemiologist


Obtaining a Master of Public Health or related Master’s Degree is typically enough to get started in an entry-level job in epidemiology. While many epidemiologists go on to work for government agencies, others may decide to concentrate on local issues and work for non-profits, local clinics, private research facilities, or university labs.

How do Epidemiologists Use Data to Track Diseases?


A large part of the work that epidemiologists do involves collecting, interpreting, and analyzing data to identify specific patterns. Epidemiologists start by forming a typical case definition. This makes sure that cases can be counted across the globe using the same defined parameters.


Once epidemiologists are all on a level playing field, they start to collect information about cases in what’s known as public health surveillance, or the systematic collection, analysis, and interpretation of public health data. The data collected include incidence, prevalence, hospitalizations, and deaths.


Epidemiologists use many terms to describe the spread of infectious diseases. We’ve outlined and defined some of these epidemiology terms here.


When public health surveillance has been completed, the results are converted into charts and diagrams that make it easier to interpret patterns. What was once only achievable by experts in data visualization can now be achieved by the powerful online database software.


The Global Infectious Diseases and Epidemiology Online Network, or GIDEON, is a web-based program for decision support and informatics in Infectious Diseases and Geographic Medicine.


GIDEON is a powerful tool for prospective and professional epidemiologists alike, capable of creating custom epidemiological charts that mix 38,000+ graphs to provide quick insights on prevalence, mortality, and vaccination rates. Information analysis and visualization are also a snap with GIDEON R, an efficient plug-and-play statistical tool for cleaning, analyzing, and visualizing epidemiological data and epidemiologic research from the GIDEON database.


As an educational tool, GIDEON is unmatched. Educators in microbiology and epidemiology can put theory into context by simulating realistic scenarios and outbreaks using tools and data from GIDEON.



  • What is a simple definition of epidemiology?
    • Epidemiology is the study of what causes diseases, how they spread, and how to use that information to minimize the effect and spread of infectious diseases on populations.
  • Why is epidemiology important?
    • When an illness or disease occurs in a population or community, epidemiologists act as “disease detectives” to determine where a disease is coming from and which people that illness is most likely to impact. The quicker epidemiologists can understand the disease, the more effectively they can minimize the spread and impact.
  • What are 4 uses for epidemiology?
    • Epidemiology can be used to assess the overall health, trace the contact origins of infectious diseases, determine who is most likely to be affected by a particular disease, and provide insight into how to prevent future disease outbreaks.
  • Who defined epidemiology?
    • While the first person to popularize the term “epidemiology” is believed to be Spanish physician Joaquín de Villalba in 1802, modern organizations such as the United States Center for Disease Control (CDC) and the European Centre for Disease Prevention and Control (ECDC) uphold the contemporary definition of the word.
Kimberly Hazel

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