The Epidemiological triad Is a model that allows to evaluate the causality and the interactions of the agents that propagate an infectious disease.
The triad is a methodology that characterizes infectious diseases, because it identifies the interaction between the environmental agent, virus and host.
Epidemiological studies focus on determining causality, transmission, and historical clinical records to learn about environmental factors that, in interaction with the virus, create an environment for the reproduction of infectious disease in the host.
Each epidemiological disease is different, so the environment that supports it is complex and can vary to create the environment conducive to 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.
Components of the epidemiological triad
Knowing the interaction of the components that make up the epidemiological triad allows identifying the causality of the infectious disease. Every disease demands a unique and favorable interaction environment between the factors, environmental climate, virus and host for the growth and propagation of the virus.
The timely identification of causality and the interaction between the factors that make up the epidemiological triad makes it possible to integrate 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 inhabits the host in the right environment, causes the disease.
The agent alone does not necessarily cause the disease, that will depend on the interaction conditions between the rest of the components of the epidemiological triad, as they are; The guest and the environmental climate.
There are some characteristics that the agent must fulfill to develop an infection in the host, among them is:
The dose of infectious particles or microorganisms that increase the probability of producing disease in the host, the ability to access, grow and reproduce in the host, survival to the immune response of the host, 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 socio-economic factors.
Socioeconomic factors
Socioeconomic factors affect the host and generate the interaction conditions necessary for the development of the disease, among which are: overcrowding, access to public services, access to health services or unsanitary conditions, among others.
Physical factors
Among the salient physical factors are the environmental climate, geology, fauna, flora, ecosystem, and geographic areas.
Biological factors
Biological factors are formed by agents such as insects that transmit diseases, environmental pollutants.
Guest
The host, is the human being where it grows, and reproduces the microorganism that causes the disease. There are multiple factors that humans must meet to create the right environment for the disease to occur.
These risk factors significantly increase exposure and susceptibility to generate the conditions necessary 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 the infection can occur in a variety of ways.
Transmission by vectors
There are vectors that are responsible for transmitting infectious agents from one human to another. They are part of the process, but do not directly cause the infection.
Mosquitoes, ticks, worms, flies are some of the vectors that transmit diseases. The vectors are responsible for the transmission of diseases from one host to another.
Once the pathogenic agent or agent leaves its host it is transferred by a vector to another host with susceptibility conditions adequate to reproduce the disease.
According to a study conducted by the World Health Organization (2014), vector-borne diseases worldwide account for 17% of all infectious diseases.
Direct transmission
It is produced by the transmission of the host-to-host agent, where the agent leaves an outgoing channel to one host and enters another through an inlet conduit. Transmission is generated by direct physical contact of an infected host with a healthy host.
Sexual contacts, kissing, touching, 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 key factor to identify in the infectious process. The 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 illness in the host. In infectious diseases, time is a factor that must be taken into account in determining which stage of the infectious process the host is in.
Once the agent enters the host, it takes a specific incubation time until the appearance of the first symptoms that indicate the presence of the disease. The time factor is important to determine the epidemic curve of the disease, ie shows the levels of danger or recovery of the infectious process.
The presence of all components of the epidemiological triad allows to create 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 causation for the reproduction of an infectious disease. However, adding the rest of the factors creates an environment conducive to the reproduction and transmission of epidemics.
The epidemiological triad is a methodology used to identify the causality of the infections, the knowledge of the interaction of its components allows to control and to prevent the infectious processes.
References
- Rothman, K. (2002). Epidemiology: an introduction. Oxford: Oxford University Press. ISBN 0195135547. Available at: ncbi.nlm.nih.gov.
- Centers for Disease Control and Prevention (2002). Introduction to Epidemiology Dept. of Public Health, Atlanta. Available at: emergency.cdc.gov.
- Society, The Individual, and Medicine Canada's University. (2014). Infectious Disease Control. Available at: med.uottawa.ca.
- World Health Organization WHO (2014). Epidemiological Diseases. Regional Office for the Americas of the World Health Organization. Available at: who.int.
- Arrieta, F. (2014). Epidemiology. Department of Immunizations CHLA-EP. Uruguay. Available at: chlaep.org.uy.
- Rojas, R. (1994). Basic epidemiology in primary health care. 91-94. Ediciones Díaz de Santos, S.A. Chile. Available at: books.google.co.ve.
- Saucier, K. Janes S. (2009). Community Health Nursing. 103-106. Second Edition. United States of America. Available at: books.google.co.ve.