DP - The Epidemiologic Triangle Lesson

The Epidemiologic Triangle Lesson

Triangle with Time in middle and Host, Environment, and Agent at the vertices. When studying in science, we often use models to deepen our understanding. You have studied models for DNA, models for solving problems (equations), and models for understanding the earth's structure. Epidemiologists often use models to attempt to understand diseases. One such model is called the Epidemiological Triangle.

The Epidemiological Triangle provides a basis for understanding infectious diseases and how they are spread. You already know that a triangle has three sides and three corners called vertices. The vertices represent three concepts: the agent, the host, and the environment. The agent is the microbe that causes the disease or the what of the triangle. The host is the organism harboring the disease or the who of the triangle. Epidemiologists also discuss symptoms of the disease that affect the host. The environment consists of the factors that cause or allow disease transmission. The surroundings, places, temperatures, or even time of the year are included with the environment. On the inside of the triangle is time. Time may refer to how long the illness lasts or the incubation period. The job of an epidemiologist is to break one side of the triangle to prevent the disease from continuing.

Let's use food poisoning as an example and apply the epidemiological triangle to it. Triangle with Time in middle and Host (Symptoms include diarrhea, vomiting, nausea), Environment (human or animal digestive tracts or feces, water), and Agent (E. coli) at the vertices. We could find information about food poisoning by visiting the CDC website or by using a search engine. Through research we would find that food poisoning is often caused by the bacterium, E-coli. E-coli can be found in the intestines and wastes of people and animals. People stand a chance of getting sick when meat that is consumed is undercooked and contains E-coli. Cold temperatures or high heat can kill E-coli. That is why it is important to thoroughly cook any meat that you consume and refrigerate leftovers promptly.

The agent in this case is the E-coli bacteria. These bacteria like many others multiply quickly and can be transmitted in multiple ways. The host experiences nausea, diarrhea, and vomiting. The environment of E-coli consists of the digestive tracts of animals and people. E-coli can also live in water and infect fruits and vegetables irrigated by that water. Food poisoning caused by E-coli usually lasts 1 to 2 days.

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