what are the elements of the epidemiologic triad

• A number of models of disease causation have been proposed.
• Among the simplest of these is the epidemiologic triad or triangle, the traditional model for infectious disease.
• The triad consists of an external agent, a susceptible host, and an environment that brings the host and agent together.
• In this model, the disease results from the interaction between the agent and the susceptible host in an environment that supports the transmission of the agent from a source to ...
• While the epidemiologic triad serves as a useful model for many diseases, it has proven inadequate for cardiovascular disease, cancer, and other diseases that appear to have multiple contributing causes ...

Full Answer

What is the epidemiologic triad?

Among the simplest of these is the epidemiologic triad or triangle, the traditional model for infectious disease. The triad consists of an external agent, a susceptible host, and an environment that brings the host and agent together.

What is the triad model of disease transmission?

The triad consists of an external agent, a susceptible host, and an environment that brings the host and agent together. In this model, disease results from the interaction between the agent and the susceptible host in an environment that supports transmission of the agent from a source to that host.

What is the epidemiologic triangle?

The Epidemiologic Triangle The Epidemiologic Triangle is a model that scientists have developed for studying health problems. It can help your students understand infectious diseases and how they spread. and facts. The Triangle has three corners (called vertices): Agent, or microbe that causes the disease (the “what” of the Triangle)

What is the Triad and why is it important?

Used as an epidemiological tool, the triad is utilized to determine all factors internal and external to the host (the human), making them more susceptible to the agent (the “germ”), and has been used for decades to determine specific factors contributing to disease. Authored by: Kate Sciera, Daniel Levy, Ditue Paul, Fnu Tenzin Bhuti.

What are the 4 important elements of epidemiology?

Key terms in this definition reflect some of the important principles of epidemiology.Study. Epidemiology is a scientific discipline with sound methods of scientific inquiry at its foundation. ... Distribution. ... Determinants. ... Health-related states or events. ... Specified populations. ... Application. ... Summary.

What is the epidemiologic triad used for?

The Epidemiologic Triangle The Epidemiologic Triangle is a model that scientists have developed for studying health problems. It can help your students understand infectious diseases and how they spread.

What are the three vertices in the epidemiologic triad?

The epidemiologic triangle is made up of three components that contribute to the spread of disease: an external agent, a host and an environment in which the agent and host meet. Between the vertices, scientists will often describe the center of the triangle as representing time.

What are the key concepts of epidemiology?

Two essential concepts of epidemiology are population and comparison. Core epidemiologic tasks of a public health epidemiologist include public health surveillance, field investigation, research, evaluation, and policy development.

What are the 3 factors that cause disease?

Infectious diseases can be caused by:Bacteria. These one-cell organisms are responsible for illnesses such as strep throat, urinary tract infections and tuberculosis.Viruses. Even smaller than bacteria, viruses cause a multitude of diseases ranging from the common cold to AIDS.Fungi. ... Parasites.

What are epidemiology and explain its components?

Epidemiology is based on two fundamental assumptions. First, the occurrence of disease is not random (i.e., various factors influence the likelihood of developing disease). Second, the study of populations enables the identification of the causes and preventive factors associated with disease.

What are the types of epidemiology?

Epidemiologic studies fall into two categories: experimental and observational.

Who proposed epidemiological triad?

Tee: In 1928, in the Cutter Lecture at Harvard, Wade Hampton Frost introduced the epidemic triad. The lecture was published in AJE in 1976. In 1975, Dr. Jerry Morris, a prominent British epidemiologist, set out a list of seven uses of epidemiology.

What is the role of epidemiology?

Epidemiology is the study of diseases in populations, investigating how, when and why they occur. The diseases studied are wide-ranging, including infectious diseases like coronavirus and non-infectious diseases like arthritis. People who work in this field are referred to as epidemiologists.

What part of the epidemiological triad does the infectious agent represent?

Agent. The agent within the epidemiological triad is microbes that cause disease to occur. When considering infectious diseases, the agent is an external microorganism that needs to be present in order for the disease to occur.

How does disaster epidemiology inform the practice of healthcare?

prevent or reduce the number of deaths, illnesses, and injuries caused by disasters, provide timely and accurate health information for decision-makers, improve prevention and mitigation strategies for future disasters by collecting information for future response preparation.

What is the method used to find the causes of health outcomes and diseases in populations?

Epidemiology is the method used to find the causes of health outcomes and diseases in populations. In epidemiology, the patient is the community and individuals are viewed collectively.

Why is epidemiology important?

As noted earlier, one important use of epidemiology is to identify the factors that place some members at greater risk than others.

What is the simplest model of disease causation?

A number of models of disease causation have been proposed. Among the simplest of these is the epidemiologic triad or triangle, the traditional model for infectious disease. The triad consists of an external agent, a susceptible host, and an environment that brings the host and agent together. In this model, disease results from the interaction between the agent and the susceptible host in an environment that supports transmission of the agent from a source to that host. Two ways of depicting this model are shown in Figure 1.16.

What are the causes of disease?

Over time, the concept of agent has been broadened to include chemical and physical causes of disease or injury. These include chemical contaminants (such as the L-tryptophan contaminant responsible for eosinophilia-myalgia syndrome), as well as physical forces (such as repetitive mechanical forces associated with carpal tunnel syndrome). While the epidemiologic triad serves as a useful model for many diseases, it has proven inadequate for cardiovascular disease, cancer, and other diseases that appear to have multiple contributing causes without a single necessary one.

The Agent

Agents of infectious diseases include bacteria, viruses, parasites, fungi, and molds.

The Host

A host offers subsistence and lodging for a pathogen and may or may not develop the disease.

The Environment

The ability of the pathogen to accept the new environment can also be a determining factor because some pathogens thrive only under limited ideal conditions.

The Time

Time includes the severity of illness in relation to how long a person is infected or until the condition causes death or passes the threshold of danger towards recovery.

Agent

HIV is a viral infection that targets a person’s immune system, making it more vulnerable to other forms of infection. Because the virus targets the immune system itself, the body cannot effectively fight HIV on its own.

Host

Scientists theorize that HIV was originally carried by chimpanzees and that humans who hunted these chimpanzees for meat became infected with a mutated form of the virus upon contact with the chimpanzees’ blood.

Environment

There are a number of socio-economic factors that can impact the spread of HIV within a community. Communities with higher concentrations of sexually transmitted diseases and lower incidences of reporting — due to social pressure or otherwise — allow HIV to flourish.

What are the factors that are taken into account when considering the epidemiological triad?

When considering the Epidemiological Triad, there are three main factors that are taken into account: The Agent, The Host, and The Environment. Below is a brief description of each factor.

What is the host within the triad?

The host within the triad refers to the human capable of developing the disease. Numerous risk factors contribute to a human’s exposure, susceptibility, and response to a harmful agent. Exposure to an agent is influenced by a person’s behavior like sexual practices, hygiene, and other behavioral practices.

What are the factors that influence exposure?

Susceptibility and response are both influenced by factors like genetic composition, physiological make up, and health behaviors such as nutrition and exercise (CDC, 2012).

What is an agent in infectious disease?

When considering infectious diseases, the agent is an external microorganism that needs to be present in order for the disease to occur. These pathogens include viruses, bacteria, fungi, parasites, and other microorganisms. Many people refer the agent as the “germ.”. Over time, the concept of the agent has expanded to allow for application ...

What is the agent of infectious disease?

The agent is the cause of the disease. When studying the epidemiology of most infectious diseases, the agent is a microbe —an organism too small to be seen with the naked eye. Disease-causing microbes are bacteria, virus, fungi, and protozoa (a type of parasite). They are what most people call “germs.” Bacteria: Bacteria are single-celled organisms. Bacteria have the tools to reproduce themselves, by themselves. They are larger than viruses (but still much too small to be seen with the naked eye). They are filled with fluid and may have threadlike structures to move themselves, like a tail.

What is the triangle of time?

In the center of the Triangle is time. Most infectious diseases have an incubation period—the time between when the host is infected and when disease symptoms occur. Or, time may describe the duration of the illness or the amount of time a person can be sick before death or recovery occurs. Time also describes the period from an infection to the threshold of an epidemic for a population. These lessons do not specifically cover the time because it is a complex concept for middle school students; however, it can be covered as an extension for advanced students. Warm-up

How many episodes of chickenpox are there in a lifetime?

Most people who get the disease are under age 15, but anyone who has not had the disease is susceptible. A person usually only has one episode of chickenpox in a lifetime.

Content

The epidemiological triad It is a model that allows to evaluate the causality and interactions of the agents that spread an infectious disease. The triad is a methodology that characterizes infectious diseases, because it identifies the interaction between the environmental agent, virus and host.

Components of the epidemiological triad

Knowing the interaction of the components that make up the epidemiological triad allows us to identify the causality of the infectious disease. All disease demands a unique and conducive interaction environment between factors, environmental climate, virus and host for the growth and spread of the virus.

Agent

It is a virus, bacterium, parasite or pathogenic and infectious microorganism. The agent is the microorganism that inhabits the host in the right environment, causes the disease.

Environmental climate or environment

The environment refers to the appropriate environment that the agent or microorganism needs to develop the disease in the host. Environmental conditions are a fundamental component for the growth and spread of diseases.

Socioeconomic factors

Socio-economic factors affect the host and generate the necessary interaction conditions for the development of the disease, among them are: overcrowding, access to public services, access to health services or unsanitary conditions, among others.

Physical factors

Among the outstanding physical factors, is the environmental climate, geology, fauna, flora, ecosystem, and geographical areas.

Biological factors

Biological factors are made up of agents such as disease-transmitting insects, environmental pollutants.

What are the stages of epidemiology?

Stages of Development of Information CDC has spelled out four stages in developing public health information: public health surveillance; risk group identification; risk factor identification; and program development, implementation, and evaluation. 1. Public health surveillance – development and refinement of data systems for the ongoing and systematic collection, analysis, interpretation and dissemination of information 2. Risk group identification – identification of persons at greatest risk of disease or injury and the places, times, and other circumstances that are associated with elevated risks 3. Risk factor identification – analytic exploration of potentially causative risk factors for disease, injury or death as suggested by the high risk population and other research 4. Program development,implementation, and evaluation – design, implementation and evaluation of preventive interventions based on degree of understanding of the population-at-risk and the risk factors for the outcome of interest The first two stages fall under the realm of descriptive epidemiology. Stages three and four involve analytic epidemiology, with its capacity to evaluate both putative cause-and- effect relationships and interventions based on this etiologic understanding. Combining stages 1 and 2, and separating program development and evaluation from implementation of a tested program, the Public Health Approach take us from recognition of a public health problem through its solution (Figure 9).

What are the two types of tribuads?

1. Epidemiologic Triad (devised to enhance search for understanding communicable disease) 2. Web of Causation (devised to address chronic disease – can also be applied to communicable disease)

What is the best known model of communicable disease?

Etiology is the science of causation. The Epidemiological Triad The best known, but most dated model of communicable disease is the Epidemiologic Triad (Figure 1). This model comprises a susceptible host (the person at risk for the disease ), a disease agent ( the proximate cause ), and an environmental context for the interaction between host and agent.

What was the Wheel of Causation model used for?

One application of The Wheel of Causation model was to elucidate the potato famine that devastated Ireland in the mid-19th century. The famine was the synergistic product of a fungal invasion of potato crops, a predominantly peasant population subsisting on a potato diet, and repressive British colonial rule.

What are the levels of prevention?

Levels of Prevention: In the world of public health, we delineate three levels of prevention: primary prevention aims at preventing occurrence of a disease or injury; secondary prevention aims to minimize damage when it occurs; and tertiary prevention covers follow-up medical and hospital care and rehabilitation. The Haddon Matrix, a framework named for its creator, the engineer-physician- epidemiologist William Haddon, combined the three levels of prevention with the

What is the wheel of causality?

The Wheel of Causation The Wheel of Causation (Mausner & Kramer, 1985) de-emphasizes the agent as the sole cause of disease, while emphasizing the interplay of physical, biological and social environments (Figure 7). It also brings genetics into the mix.

What are the elements of an epidemiologic study?

The elements include identification of a relevant study population of adequate size; appropriate assessment and accurate measurement of uranium exposure in the population, including the use of biomarkers when available; an evaluation of long-term health outcomes; adequate followup time; use of reasonable methods for controlling critical confounding factors and minimizing bias; and appropriate statistical analyses. Key issues related to sample size requirements for ensuring adequate statistical power in detecting small effects, the accuracy of exposure measurement, and the need to control critical confounders are addressed in detail. The chapter also briefly describes the various types of epidemiologic studies.

How to assess exposure in occupational epidemiology?

One approach to assessing exposure in occupational epidemiologic studies is to approximate individual exposure by modeling cumulative exposure on the basis of a worker’s job history and the level of exposure in each worksite. Exposure to a particular agent is measured in various worksites. This information is used to model the cumulative lung dose per unit time in the worksite. Employment records are then used to determine the amount of time that each worker spent in each job and the worker’s cumulative exposure in all worksites over the course of his or her employment.

What is the importance of accurate characterization of information on exposure?

Accurate characterization of information on exposure is an essential component of an epidemiologic study. Rothman and Greenland (1998) note that the “quality of exposure measurement will determine the validity of an environmental epidemiology study…. The importance of exposure assessment in environmental epidemiology cannot be overstated.”

How to reduce sampling error in epidemiology?

A representative sample that is large enough will be more likely to capture accurate information about a purported association. In fact, a primary method of reducing sampling error in an epidemiologic study is to enlarge the sample.

How to collect exposure information?

Other methods of collecting exposure information include face-to-face or telephone interviews, questionnaires distributed by mail or electronically, and combinations of these. Depending on the type of information needed for a study, a combination may be appropriate. When cost is a factor, a secure electronic questionnaire or survey is an appealing option. Face-to-face interviewing is generally considered a more reliable method of obtaining information because interviewers have the opportunity to observe study participants, ask followup questions, and clarify responses (IOM, 1999). Telephone interviewing and mail surveys are less expensive than face-to-face interviews, but may result in higher nonresponse rates. And mail surveys may encourage more honest responses.

How many subjects would need to be enrolled to detect a RR of 1.50?

The calculations suggest that about 9,000 subjects would need to be enrolled to detect a RR of 1.50.

Is DU exposure a relative risk?

The committee acknowledges the difficulty of detecting such a small relative risk in epidemiologic studies. In addition to the large sample size requirement and the expected small effect of DU exposure on the health outcome of interest, adjustment for other potential confounding factors (that is, factors associated with both DU exposure and the health outcome of interest) is challenging. Furthermore, even if other factors are controlled for in the analysis, the question of whether any observed effects might be explained by residual confounding remains. Issues related to confounding are discussed in greater detail below.