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How Does Epidemiology Relate To Public Health?

July 09, 2020
person explaining to 4 others with a blackboard in the background.
Here in the summer of 2020, it’s all too easy to think of epidemiology—the method used to find the causes of health outcomes and diseases in populations1—as being all COVID-19, all the time. While infectious disease epidemiology plays a large role in each day’s news and the national consciousness, the broader study of epidemiology considers a wide range of public health problems and events. In this post, we’ll look at the bigger picture.


Often described as the basic science of public health, epidemiology is the scientific, systematic and data-driven study of the frequency, pattern, causes and risk factors of health-related states and events in specified populations.2 It is also the application of this study to the control of health problems3. The Centers for Disease Control and Prevention (CDC) notes that, in epidemiology, the patient is the community and individuals are viewed collectively.

The CDC goes on to list the following six areas of epidemiological investigation.

Environmental Exposures

In addition to air pollutants and other asthma triggers, this category includes hazards found in human-made items around us. Human exposure to lead, for example, “usually results from lead in deteriorating household paints, lead in the workplace, lead in crystals and ceramic containers that leaches into water and food, lead use in hobbies, and lead use in some traditional medicines and cosmetics.”3 The National Institutes for Health cites reports that “among 16.4 million United States homes with more than one child younger than 6 years per household, 25 percent of homes still had significant amounts of lead-contaminated deteriorated paint, dust, or adjacent bare soil. Lead in dust and soil often re-contaminates cleaned houses and contributes to elevating blood lead concentrations in children who play on bare, contaminated soil.”3

Infectious Diseases

Beyond influenza, pneumonia and other notable reasons to cover our coughs, the world of infectious disease is rife with foodborne illnesses. According to the U.S. Food and Drug Administration, many outbreaks and individual cases result from consuming the two most common types of foodborne pathogens: bacteria (such as Salmonella, Listeria or E. coli) and viruses (such as norovirus or hepatitis A).4

Foodborne illnesses can get into our systems through unpasteurized milk and fruit juices, and contaminated meats, eggs, produce, spices, nuts and water—as well as through person-to-person transmission. Given how frequently we can encounter those risk factors, it’s no surprise that the U.S. sees about 48 million cases of foodborne illnesses each year.4


This category often comprises deliberate threats and harm, including surges in homicides and domestic violence (also known as intimate partner violence) within any given community.

An article published in May, 2020 by the Council on Foreign Relations documents recent statistics on domestic violence: “According to data collected by the United Nations, 243 million women and girls between the ages of 15 and 49 worldwide were subjected to sexual or physical violence by an intimate partner in the last 12 months. Put a different way, one in three women has experienced physical or sexual violence at some point in her life. LGBTQ+ individuals experience similarly high levels of violence.”5

As grim as those numbers are, the article goes on to paint a more disturbing picture. “Today, rising numbers of sick people, growing unemployment, increased anxiety and financial stress, and a scarcity of community resources have set the stage for an exacerbated domestic violence crisis. Many victims find themselves isolated in violent homes, without access to resources or friend and family networks. Abusers could experience heightened financial pressures and stress, increase their consumption of alcohol or drugs, and purchase or hoard guns as an emergency measure. Experts have characterized an ‘invisible pandemic’ of domestic violence during the COVID-19 crisis as a ‘ticking time bomb’ or a ‘perfect storm.’”5

Non-Infectious Diseases

Periodic news of cancer and other diseases caused by nearby water pollution is so much a part of our public consciousness that it has become fodder for Hollywood, as films such as Erin Brockovich attest.

Epidemiology in this area includes other acute problems. In January of 2016, CNN reported on the rise of a serious birth defect called gastroschisis, which can cause the intestines to poke through a newborn's abdomen. The report cited a CDC finding that the number of cases nearly doubled between 1995 and 2005, and has continued to rise since then.

"’It concerns us that we don't know why more babies are being born with this serious birth defect. Public health research is urgently needed to figure out the cause and why certain women are at higher risk of having a baby born with gastroschisis,’ said Coleen Boyle, the director of the CDC's National Center on Birth Defects and Developmental Disabilities.”6

Natural Disasters

Consider the profound, ongoing health risks facing people who don’t have safe shelter: exposure to extreme heat and cold, malnutrition, dehydration, threats to sexual and physical safety, lung disease, wounds and skin infections, musculoskeletal disorders and a host of other mental and physical illnesses.

Then consider:

  • In 2005, 200,000 homes were lost to Hurricane Katrina7
  • In 2010, a magnitude-7.3 earthquake in Haiti left more than 1.5 million people homeless8
  • In 2017, Hurricane Harvey destroyed nearly 17,000 homes in Texas alone9

These numbers refer solely to homelessness caused by specific events. A California news report in January of this year cited that, “As many as 3.5 million Americans are homeless, according to the Department of Housing and Urban Development.”10


The term quickly calls to mind bombs and guns. The devastating results of the September 11 attacks and the Murrah Federal Building bombing are immediate, horrifying examples.

Epidemiology in this category goes further, however, to include biological assaults. The Federal Bureau of Investigation’s website includes this record: “Soon after the terrorist attacks of 9/11, letters laced with anthrax began appearing in the U.S. mail. Five Americans were killed and 17 were sickened in what became the worst biological attacks in U.S. history.”11


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