Epidemiological Frameworks: Chain of Transmission (Nursing)

by Heide Cygan, DNP, RN

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    00:01 Today we're going to talk about an epidemiological framework called the chain of transmission.

    00:06 We use the chain of transmission to understand how diseases are spread from person to person.

    00:12 Now there are six links in this chain.

    00:14 And in order to prevent disease, all we have to do is break the connection between two of those links.

    00:20 So let's take a look at each.

    00:23 We'll start first with the agent.

    00:25 This is what causes disease to occur.

    00:27 And remember, there are five different types of agents: biological, chemical, nutrient, physical, and psychological.

    00:36 Next, we have the reservoir, and this is the place where the agent can live and multiply.

    00:42 Examples include humans, rats, squirrels, and a few other animals.

    00:49 Next, we have the portal of exit.

    00:52 Now the agent has to have a way to escape to get out of the reservoir.

    00:56 And that's what this is the portal of exit.

    01:01 And now it's important for us to identify the mode of transmission, there are several possibilities here.

    01:07 The agent could be spread through direct contact, such as kissing an infected individual.

    01:13 Or the mode of transmission could be indirect spread, such as food or waterborne illnesses, or an agent can be spread by vector only.

    01:22 And remember, a vector is a nonhuman carrier of disease.

    01:27 Next, we have the portal of entry.

    01:29 This is the way that the agent gets into the host body.

    01:34 And then finally, we have the host.

    01:36 This is the individual who is susceptible to being infected by that agent.

    01:41 Now again, there's six parts here.

    01:43 And as long as they all connect, diseases can be spread.

    01:46 However, all you have to do to stop the spread of infection is to break the chain in just one place.

    01:53 It's also important to take into consideration the environment.

    01:57 The circle surrounding the chain here represents the environment, which can have a profound influence at almost any point in the chain.

    02:06 So let's walk through application of the chain of transmission for the disease process of malaria.

    02:12 We'll start first with the agent.

    02:14 Now remember, the agent is what causes harm.

    02:17 In this instance, the agent is the parasite that causes malaria.

    02:22 Now, can you think of what type of agent that would be? If you said a biological agent, you are right.

    02:30 Next we have the reservoir.

    02:32 So this is a person who's already been infected with malaria, they've come in contact with that agent.

    02:39 Next, we have the portal of exit.

    02:42 Now remember, in order for disease to spread, we need a way for the agent to exit the reservoir.

    02:47 This is called the portal of exit.

    02:50 In the case of malaria, the only way for the agent to spread is through a vector specifically through a mosquito.

    02:56 So the mosquito bite on the reservoir is the portal of exit.

    03:02 Next, we have the mode of transmission.

    03:04 And as I just said, we need a mosquito to transmit the parasite from the reservoir to another person.

    03:10 So this means the mode of transmission is vector transmission.

    03:16 Next, we have the portal of entry.

    03:18 So we need a way for that agent to get into the susceptible host body.

    03:22 In the case of malaria, the mosquito bite provides the portal of exit and the portal of entry.

    03:28 However, the portal of entry is the mosquito bite on the new susceptible person.

    03:34 And then finally, we have that person here we have the susceptible host, who if bitten by the vector is at risk of getting malaria.

    03:45 Now let's think about the environment.

    03:46 For malaria, a vector is needed to transmit the disease.

    03:50 So we have to take into consideration the environmental factors that encourage vector reproduction and growth.

    03:58 So as I said earlier, the way that we stop infection is by breaking this chain.

    04:04 So let's think of some ways that we can break this chain up.

    04:08 What's one way to stop the spread of malaria? If you want it to break the chain links between the vector and the portal of entry, what is one strategy that you might use? So essentially, what I'm asking is, how would you prevent the mosquito from biting the susceptible host? Well, what about the use of mosquito nets? This could prevent the mosquito from creating a portal of entry by biting the potential host.

    04:33 Or what about the environment? You could take into consideration environmental efforts that would eliminate the vector.

    04:40 We know that mosquitoes thrive in areas with standing water.

    04:43 So by eliminating that standing water, we can eliminate the vector and break the chain.

    04:49 The chain of transmission is an epidemiological model that explains how diseases are spread.

    04:54 And it gives us the information that we need to develop interventions that protect individuals and entire communities.

    About the Lecture

    The lecture Epidemiological Frameworks: Chain of Transmission (Nursing) by Heide Cygan, DNP, RN is from the course Epidemiology (Nursing).

    Included Quiz Questions

    1. Mode of transmission
    2. Infectious agent
    3. Environment
    4. Susceptible host
    1. The tick bite
    2. The tick
    3. Rocky Mountain Spotted Fever
    4. The vector

    Author of lecture Epidemiological Frameworks: Chain of Transmission (Nursing)

     Heide Cygan, DNP, RN

    Heide Cygan, DNP, RN

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