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When epidemiologists are working to track a disease, the three


When epidemiologists are working to track a disease, the three elements that they focus on are the agent, the host, and the environment. Following are explanations of each element.

The agent is what causes the disease. The agent is often a virus or bacteria but can also be caused by other agents. In the scenario, described in the Introduction, the agent is the E.coli bacteria. 

The host refers to those who are contracting the disease. The host doesn’t necessarily become sick. Hosts can serve as carriers of the disease who do not show outward signs or symptoms. 

Finally, the environment refers to the external factors that support or cause the disease to spread. In the E. coli scenario, the lettuce became infected either at the farm or during transport; the lettuce was sold to the distributor and then to Sam’s Sandwich trucks; and people ate the lettuce on these sandwiches.

Each of these steps is important to tracking the disease, and epidemiologists work diligently to trace and report each of the steps to prevent further transmission of the disease.

The following is an example of an epidemiologic triad.

  • Agent: Salmonella bacteria
    • Keep in mind that agents can be biologic (e.g., bacteria or viruses), chemical (e.g., poisons or alcohol), physical (e.g., trauma or radiation), or nutritional (e.g., a lack or excess of essential nutrients).
  • Host factors: Individuals who are particularly vulnerable (e.g., the very young or very old and immunocompromised individuals).
    • Note that, in general, host characteristics can include age, sex, race, religion, customs, occupation, genetic factors, other health factors, and immunologic status.
  • Environmental factors: Contaminated kitchen surfaces or utensils, undercooking of contaminated food items, or contaminated chicken.
    • Environmental factors can include temperature, crowding, noise, pollution, food, and radiation.

Changes in one factor in the epidemiological triad can influence the occurrence of disease by increasing or decreasing a person’s risk for disease. Consider how variations in each factor, shown in the example, can influence the manifestation of disease. Refer to pages 435-440 in your Friis and Sellers (2021) textbook for further explanation.

In this Discussion, you will apply the epidemiologic triad to a disease of your choice to gain a better understanding of both the model and the disease. 

To prepare  for this Discussion: 

Access and review the Epidemiological Triad Learning Interaction.

Select an infectious disease from the list proved in List of Infectious Diseases document for Week 1 Discussion. 

Review the Week 1 “Ebola Virus Disease in the Light of Epidemiological Triad” (Kaur, Sachdeva, Jha, & Sulania, 2017) resource. Consider how the epidemiologic triad/triangle can be applied to your selected disease.

Consider how variations in each factor shown in the example from the textbook can influence the manifestation of the disease. Refer to pages 435-440, in your textbook, for further explanation.

By Day 4

Post a comprehensive explanation of the following:  

  • Identify  ebola virus disease Following are explanations of each element. 
  • Provide an example of an agent that is associated with the infectious disease that you selected. 
  • Discuss  at least three  examples of environmental factors that contribute to the likelihood of transmission of the agent to an individual for the disease you have selected. 
  • Discuss at least three  examples of host factors that contribute to the likelihood of transmission of the agent to an individual for the disease you have selected.  

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