What is epidemiology?

What is epidemiology?

Epidemiology is the study of the distribution and determinants of health problems in specified populations and the application of this study to control health problems. Epidemiology is the scientific method used by "disease detectives"—epidemiologists to get to the root of a public health problem or emerging public health event affecting a specific population.

Examples of populations include:

  • Residents of a neighborhood
  • Citizens of particular, county, state, territory, or country
  • Students within a school
  • Patients at a healthcare facility
  • The global community

Epidemiologists often focus on sub-populations, particular groups of people within larger populations. Often certain characteristics might make subpopulations more at risk for certain diseases. Examples of sub-populations may include:

  • Residents of a neighborhood living closest to an industrial area
  • Citizens of a particular racial or ethnic background within a city
  • Students of a certain age within a school
  • Patients residing in a particular wing of a healthcare facility

What public health problems or events are investigated?

There are many examples of health problems and events investigated by epidemiologists, we have listed some examples below.

Environmental exposures

  • Lead and heavy metals
  • Air pollutants and other asthma triggers

Infectious diseases

  • Foodborne illness
  • Influenza and pneumonia


  • Increased homicides in a community
  • Injuries occurring in a particular workplace or industry

Non-infectious diseases

  • Localized or widespread rise in a particular type of cancer
  • Increases in a major birth defect

Natural disasters

  • Injuries, illness, and deaths from Hurricanes Katrina and Rita (2005)
  • Injuries, illness, and deaths from Haiti earthquake (2010)


  • Injuries, illness, and deaths from the World Trade Center bombing (2001)
  • Illness and death from an intentional Anthrax release (2001)

Who are epidemiologists?

Epidemiologists are public health professionals who investigate causes of disease, identify people who are at risk, determine how to control or stop the spread, or prevent it from happening again.

Various professional backgrounds in public health or health care (e.g., physicians, veterinarians, nurses, or others) may be trained in epidemiology, but many epidemiologists have been trained specifically for this field. Epidemiology training generally includes the study of population statistics along with other topics such as program evaluation, biology, and health policy.

What do epidemiologists do?

Like investigators at the scene of a crime, disease detectives begin by looking for clues. They systematically gather information, asking questions such as:

  • Who is sick?
  • What are their symptoms?
  • When did they get sick?
  • Where could they have been exposed?

Using statistical analysis, epidemiologists study answers to these questions to find out how a particular health problem was introduced and spread through a population. 

Sometimes these investigations result in disease detectives identifying new diseases that have never been seen before, such as Legionnaire's disease or SARS – as well as the organisms that cause them.

Disease detectives use what they learn during the investigation and make recommendations to control the spread or prevent a future occurrence.

For more details please visit www.cdc.gov

More definitions on epidemiology

  1. Definition from WHO
  2. Definition from biomedical journal
  3. Definition from Wikipedia
  4. Definition from FAO
  5. Definition from Webster dictionary
Last modified: Friday, 3 February 2017, 10:55 AM