Epidemiological Triad Definition and Components

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

Studies of an epidemiological nature focus on determining causality, transmission, historical clinical records, to know the environmental factors that in interaction with the virus create an environment for the reproduction of the infectious disease in the host..

Each epidemiological disease is different, therefore, the environment that supports it is complex and can vary to create the environment conducive to producing the disease.

The components that make up the epidemiological triad can vary in such a way to generate the necessary interaction between the environment, virus and host so that the disease has an environment conducive to its proliferation..

Article index

• 1 Components of the epidemiological triad
  • 1.1 Agent
  • 1.2 Environmental climate or environment
  • 1.3 Guest
• 2 Transmission of infection
  • 2.1 Transmission by vectors
• 3 Another factor: time
• 4 References

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..

The timely identification of causality and the interaction between the factors that make up the epidemiological triad allows integrating timely measures for the prevention and control of the disease..

Agent

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

The agent alone does not necessarily cause the disease, that will depend on the conditions of interaction between the rest of the components of the epidemiological triad, as they are; the host and the environmental climate.

There are some characteristics that the agent must meet to develop an infection in the host, including:

The dose of infectious particles or microorganisms that increase the probability of producing the disease in the host, the ability to access, grow and reproduce in the host, survival to the host's immune response, among others.

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.

Environmental conditions can be divided into physical factors, biological factors, and socioeconomic factors..

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.

Guest

The host is the human being where the disease-causing microorganism grows and reproduces. There are multiple factors that humans must meet to create the right environment for disease to occur.

These risk factors significantly increase exposure and susceptibility to generate the necessary conditions to house the pathogen within the body..

Among the relevant factors are: sex, race, immune response, substance use, nutrition, genetics, anatomy, among others..

Transmission of infection

The epidemiological triad makes it possible to identify the causality of the infectious disease. Transmission of infection can occur in various ways.

Vector transmission

There are vectors that are responsible for transmitting infectious agents from one human being to another. They are part of the process, but they do not directly cause the infection.

Mosquitoes, ticks, worms, flies, are some of the vectors that transmit diseases. Vectors are responsible for the transmission of diseases from one host to another.

Once the pathogenic microorganism or agent leaves its host, it is transferred by a vector to another host with suitable susceptibility conditions to reproduce the disease..

According to a study carried out by the World Health Organization (2014), diseases transmitted by vectors worldwide represent 17% of all infectious diseases.

Direct drive

It is produced by the transmission of the agent from host to host, where the agent leaves one host through an exit channel and enters another through an entry conduit. Transmission is generated by direct physical contact of an infected host with a healthy host.

Sexual contacts, kisses, touch, secretions, fluids, wounds are some of the mechanisms of direct transmission of infectious diseases from one host to another..

Another factor: time

Time is another fundamental factor to identify in the infectious process. Incubation time may vary depending on the pathogen and its interaction with the environmental climate and the host..

Time refers to the course and duration of the disease in the host. In infectious diseases, time is a factor that must be taken into account to determine in which stage of the infectious process the host is..

Once the agent enters the host, it takes a specific incubation time until the first symptoms that signal the presence of the disease appear. The time factor is important to determine the epidemic curve of the disease, that is, it shows the levels of danger or recovery from the infectious process.

The presence of all the components of the epidemiological triad allows creating the right environment for a pathogen to have the conditions to reproduce within the host and develop an infectious disease.

For the control of infectious diseases, epidemiologists focus on modifying or altering some of the components of the epidemiological triad to control the spread of infection.

A component of the triad alone is not sufficient causality for the reproduction of an infectious disease. However, when the rest of the factors are added, an environment conducive to the reproduction and transmission of epidemics is created..

The epidemiological triad is a methodology used to identify the causality of infections, knowledge of the interaction of its components allows to control and prevent infectious processes.

References

1. Rothman, K. (2002) Epidemiology: an introduction.Oxford:Oxford University Press. ISBN 0195135547.Available at: ncbi.nlm.nih.gov.
2. Centers for Disease Control and Prevention (2002). Introduction to Epidemiology Dept. of Public Health, Atlanta. Available at: emergency.cdc.gov.
3. Society, The Individual, and medicine Canada's University. (2014). Infectious Disease Control. Available at: med.uottawa.ca.
4. World Health Organization WHO (2014). Epidemiological Diseases. Regional Office for the Americas of the World Health Organization. Available at: who.int.
5. Arrieta, F. (2014). Epidemiology. CHLA-EP Immunization Department. Uruguay. Available at: chlaep.org.uy.
6. Rojas, R. (1994). Basic epidemiology in primary health care. 91-94. Ediciones Díaz de Santos, S.A. Chili. Available at: books.google.co.ve.
7. Saucier, K. Janes S. (2009). Community Health Nursing. 103-106. Second Edition. United States of America. Available at: books.google.co.ve.