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Epi-Demi-ology
Epi = on or upon
Demos = people
Logos = the study of
In other words, the word epidemiology has its roots in the study of what befalls a population.
Epidemiology defined
“The work of epidemiology is related to unanswered questions, but also to unquestioned answers.” Patricia Buffler
Epidemiology is a scientific discipline with sound methods of scientific inquiry at its foundation. Epidemiology is data-driven and relies on a systematic and unbiased approach to the collection, analysis, and interpretation of data.
Epidemiology is often described as the basic science of public health. Epidemiology relies on a working knowledge of probability, statistics, and sound research methods. Epidemiology is a method of causal reasoning based on developing and testing hypotheses grounded in such scientific fields as biology, behavioral sciences, physics, and ergonomics to explain health-related behaviors, states, and events. Epidemiology provides the foundation for directing practical and appropriate public health action based on this science and causal reasoning.
frequency and pattern
Frequency refers not only to the number of health events such as the number of cases of meningitis or diabetes in a population, but also to the relationship of that number to the size of the population. The resulting rate allows epidemiologists to compare disease occurrence across different populations.
Pattern refers to the occurrence of health-related events by time, place, and person. Time patterns may be annual, seasonal, weekly, daily, hourly, weekday versus weekend, or any other breakdown of time that may influence disease or injury occurrence. Place patterns include geographic variation, urban/rural differences, and location of work sites or schools. Personal characteristics include demographic factors which may be related to risk of illness, injury, or disability such as age, sex, marital status, and socioeconomic status, as well as behaviors and environmental exposures.
DETERMINANTS
Epidemiology is also used to search for determinants, which are the causes and other factors that influence the occurrence of disease and other health-related events.
Epidemiologists assume that illness does not occur randomly in a population, but happens only when the right accumulation of risk factors or determinants exists in an individual.
To search for these determinants, epidemiologists use analytic epidemiology or epidemiologic studies to provide the “Why” and “How” of such events. They assess whether groups with different rates of disease differ in their demographic characteristics, genetic or immunologic make-up, behaviors, environmental exposures, or other so-called potential risk factors.
THE PATIENT
Although epidemiologists and direct health-care providers (clinicians) are both concerned with occurrence and control of disease, they differ greatly in how they view “the patient.”
The clinician is concerned about the health of an individual; the epidemiologist is concerned about the collective health of the people in a community or population. In other words, the clinician’s “patient” is the individual; the epidemiologist’s “patient” is the community. Therefore, the clinician and the epidemiologist have different responsibilities when faced with a person with illness.
For example, when a patient with disease presents, both are interested in establishing the correct diagnosis. However, while the clinician usually focuses on treating and caring for the individual, the epidemiologist focuses on identifying the exposure or source that caused the illness; the number of other persons who may have been similarly exposed; the potential for further spread in the community; and interventions to prevent additional cases or recurrences.
Epidemiology in action
In the mid-1800s, an anesthesiologist named John Snow was conducting a series of investigations in London that warrant his being considered the “father of field epidemiology.”
Twenty years before the development of the microscope, Snow conducted studies of cholera outbreaks both to discover the cause of disease and to prevent its recurrence.
Snow conducted one of his now famous studies in 1854 when an epidemic of cholera erupted in the Golden Square of London. He began his investigation by determining where in this area persons with cholera lived and worked. He marked each residence on a map of the area. Today, this type of map, showing the geographic distribution of cases, is called a spot map.
Because Snow believed that water was a source of infection for cholera, he marked the location of water pumps on his spot map, then looked for a relationship between the distribution of households with cases of cholera and the location of pumps.
He noticed that more case households clustered around Pump A, the Broad Street pump, than around Pump B or C. When he questioned residents who lived in the Golden Square area, he was told that they avoided Pump B because it was grossly contaminated, and that Pump C was located too inconveniently for most of them.
From this information, Snow concluded that the Broad Street pump (Pump A) was the primary source of water and the most likely source of infection for most persons with cholera in the Golden Square area. He noted with curiosity, however, that no cases of cholera had occurred in a two-block area just to the east of the Broad Street pump. Upon investigating, Snow found a brewery located there with a deep well on the premises. Brewery workers got their water from this well, and also received a daily portion of malt liquor. Access to these uncontaminated rations could explain why none of the brewery’s employees contracted cholera.
To confirm that the Broad Street pump was the source of the epidemic, Snow gathered information on where persons with cholera had obtained their water. Consumption of water from the Broad Street pump was the one common factor among the cholera patients. After Snow presented his findings to municipal officials, the handle of the pump was removed and the outbreak ended. The site of the pump is now marked by a plaque mounted on the wall outside of the appropriately named John Snow Pub.
Practice
Epidemiology and the information generated by epidemiologic methods have been used in many ways.
Assessing the Community’s Health
Public health officials responsible for policy development, implementation, and evaluation use epidemiologic information as a factual framework for decision making.
To assess the health of a population or community, relevant sources of data must be identified and analyzed by person, place, and time (descriptive epidemiology).
- What are the actual and potential health problems in the community?
- Where are they occurring?
- Which populations are at increased risk?
- Which problems have declined over time?
- Which ones are increasing or have the potential to increase?
- How do these patterns relate to the level and distribution of public health services available?
Making Individual Decisions
Many individuals may not realize that they use epidemiologic information to make daily decisions affecting their health. When persons decide to quit smoking, climb the stairs rather than wait for an elevator, or eat a salad rather than a cheeseburger with fries for lunch, they may be influenced, consciously or unconsciously, by epidemiologists’ assessment of risk. These and hundreds of other epidemiologic findings are directly relevant to the choices people make every day, choices that affect their health over a lifetime.
Completing the Clinical Picture
When investigating a disease outbreak, epidemiologists rely on health-care providers to establish the proper diagnosis of individual patients. But epidemiologists also contribute to physicians’ understanding of the clinical picture and natural history of disease.
Epidemiologists, clinicians, and researchers around the world have collaborated to characterize SARS, a disease caused by a new type of coronavirus that emerged in China in late 2002. Epidemiology has also been instrumental in characterizing many non-acute diseases, such as the numerous conditions associated with cigarette smoking — from pulmonary and heart disease to lip, throat, and lung cancer.
Searching for Causes
Much epidemiologic research is devoted to searching for causal factors that influence one’s risk of disease. Ideally, the goal is to identify a cause so that appropriate public health action might be taken. One can argue that epidemiology can never prove a causal relationship between an exposure and a disease, since much of epidemiology is based on ecologic reasoning. Nevertheless, epidemiology often provides enough information to support effective action.
Think like an Epidemiologist
In August 1999, epidemiologists learned of a cluster of cases of encephalitis caused by West Nile virus infection among residents of Queens, New York. West Nile virus infection, transmitted by mosquitoes, had never before been identified in North America.
Click on the link below (Exercise 1.2) to see how this information would be applied to assessing the community’s health, making decisions about individual patients, documenting the clinical picture of the illness, and searching for causes to prevent future outbreaks
Play the Game
Your mission, if you choose to accept, is to get clues and analyze data to Solve the Outbreak and save lives. In this fun, interactive app you get to try your hand at becoming a Disease Detective. You’ll travel the world chasing outbreaks like the ones real-life CDC Disease Detectives help fight. Should you quarantine the town, send for more lab results, or alert the media?
The better your answers, the faster you’ll climb the ranks and achieve Disease Detective status! Master Level 1 to unlock even more exciting scenarios and earn honors for your demonstrated expertise!
On the Job
Some of the areas an epidemiology career could lead include:
Academic Research Epidemiologist
This career area finds epidemiologists employed in academic centers or universities. It involves researching the different factors that cause diseases or conditions and in some cases those in the field will go on to become a professor. Their work usually leads to major discoveries that can influence the health field as a whole and may also impact policies related to public health.
Specialists in this field often direct and plan studies of serious public health issues to learn about ways to treat and prevent health problems. Also, they collect and analyze vital public health information with observations, interviews, blood and other bodily samples, to best determine causes of disease.
As with all epidemiologists, you need at least an MPH, and some in academia require a Ph.D.
Infection Control Epidemiologist
An infection control epidemiologist deals with public health problems within a hospital or a medical facility. They collect and analyze health-related data within the facility through observations, surveys, interviews, blood samples and other bodily samples.
Infection control epidemiologists often deal with problems such as MRSA within a hospital, enforcement of hygiene issues, and general cleanliness to prevent spread of infection.
The majority of these professionals worth for state and local hospitals, while some also work for university hospitals.
You need to have a master’s degree in epidemiology, which will include classes in public health, biological and physical sciences, math and statistics.
Clinical Trial Research Epidemiologist
These experts usually work for health organizations or drug companies. They complete clinical trials of drugs and procedures and monitor side effects and results. The overall goal is to find new treatments and medications for various drugs. They usually work in labs in the field, and their focus is on reducing the number of negative health outcomes.
Note that a clinical trial research epidemiologist does not work with individual patients where he or she cares for them at the bedside. Rather, they work behind the scenes to make health and wellness better for many patients.
You will need to earn a master’s degree in public health or epidemiology for this occupation.
Field Epidemiologists
These professionals are the ones made famous by movies like “Outbreak”. They work in health departments and actually are dispatched to various locations around the nation or even the world when an outbreak of disease occurs. They’ll work to identify the disease, determine its cause, and work to stem the spread of the disease accordingly.
The focus of the work of this professional is to study disease and to change how it spreads. A field epidemiologist can work in many areas, such as environmental health, infectious diseases, chronic disease and oral health.
A master’s degree in epidemiology is required to become a field epidemiologist.
Applied Epidemiologist
These professionals usually work in health agencies or departments at a national, state, or local level. Examples of employers include the CDC or the FDA. This career area focuses on investigation of disease distribution and risk factors.
Applied epidemiologists often plan or direct clinical studies of pressing public health problems, to learn ways to prevent such problems from recurring. They also collect a great deal of public health information by conducting interviews, making observations, taking blood samples, as well as taking samples of other bodily fluids.
Essentially they work to identify the areas that are susceptible to a certain illness, why that is, and what can be done to overcome the problem.
The field of applied epidemiology requires you to earn at least a master’s degree. Note that if you want to direct research projects, you will probably need to have a Ph.D.
Epidemiology Investigator
An epidemiology investigator does assessments in populations where typically there are chronic disease problems and specific trends of infection. These professionals gather biological samples, and also study the demographics of populations to determine how likely they are to get infections.
These investigators also look at environmental concerns that could have an impact on public health. They might interact with the local community to gather more evidence, and also collect biological samples. Then, those samples and information are analyzed to come up with a theory for cause and to devise a treatment intervention to stop the spread of disease.
An MPH is necessary to work in this field, which takes 2-3 years to complete.
Pharmaceutical Epidemiologist
A pharmaceutical epidemiologist studies what causes how various pharmaceuticals affect a given human population. They do research and clinical studies on how pharmaceuticals affect health and physiology. They also look at social trends and habits that could spread certain diseases.
These professionals spend much of their time in the laboratory, as they look at how chemicals react with tissue samples. They typically analyze such results and then relate them to findings in the community.
As you earn an MPH to move into this field, you will need to take classes in public health, biology, chemistry and statistics.
Ph.D. Epidemiologist
A Ph.D. epidemiologist holds a doctorate in the field, and typically will hold major leadership positions in a research facility, university, or possibly be the head of a major research study.
If you have a Ph.D. in this field, you can possibly work as a statistician that analyzes data and statistics as it relates to many infectious diseases. Also, you could work as a research scientist who researches how infectious diseases spread. Or, you could manage a research project of various kinds that could involve many branches of epidemiology.
Another common career path for the Ph.D. in this field is college professor. Someone with a doctorate can become a full professor at many universities around the US.
It takes at least four years of full time study to earn a Ph.D. as an epidemiologist. Some programs allow you to earn your MPH and then your Ph.D. together, in less time than it would take separately.
Supervisory Epidemiologist
A supervisory epidemiologist is one who has taken a senior management or supervisory role in an organization. This professional will oversee a large team of junior epidemiologists, and will need to effectively manage research efforts. The main goal of this professional is to better public health through effective research, which a supervisory epidemiologist can have a major effect upon.
This advanced professional typically will advise other epidemiologists to gather and compile data, and to then perform analysis to learn more about the disease. It also is very important for this professional to ensure that all regulations are being closely followed.
In addition to having an MPH, you will need to have several years of experience in the field to become a supervisor.
State Epidemiologist
A state epidemiologist also investigates causes of disease and how to prevent them from spreading, just as a regular epidemiologist does. However, the focus in this career is on the health of the population in a single state. This means that you generally will be working for a state government, and will provide vital services to help people avoid disease and illness.
You may plan public health studies in the state, develop and implement them, and also collect and gather samples and data. You then will organize and analyze all of this data, and present findings to stakeholders within the government.
A state epidemiologist may work on issues specific to that state, such as substance abuse, chronic disease or bioterrorism.
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