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Skip to 0 minutes and 9 seconds OK. Let’s start this session now. What we’re going to do is we will start to learn how to design a simulation model, agent-based simulation. This simulation that you are going to design is for cholera. We are actually trying to simulate an epidemic outbreak of cholera in 2005. This outbreak happened in Kumasi, which is an inland city, a large city. What I would like you to do is think of two transmission mechanisms for cholera. One is the primary transmission, which is from the environment to the human being. But I would like you also to think about the secondary transmission, which is via the digestive system.

Skip to 1 minute and 7 seconds So if someone is ill, that person might shed– let’s say fluids, which contain a hyper-infectious version of the cholera bacteria.

Skip to 1 minute and 26 seconds Now, what we would like you to do is start with the process. We’d like you to think about a process of cholera diffusion in this particular city. What I will do is I will give you five minutes. This is an individual exercise. And you simply write down all the elements that you associate with the process of cholera diffusion in Kumasi. After these five minutes, what we will do is we will together evaluate the results. Any questions? OK. Five minutes.

Skip to 2 minutes and 28 seconds I see that most of you are ready. Even if you’re not completely ready, that doesn’t matter. Let’s see if we can put all your suggestions, all the elements that you put on paper, together. And I’ll be using the white board, and together we will draw an overview of our design. OK? I will randomly ask you to tell me something about what you have identified for this process. And you can just add on elements to what previous students already mentioned. So the first one I thought of was drinking contaminated water from a river or something.

Skip to 3 minutes and 31 seconds My idea is that perhaps the mother of a household who has been unwell, she might have poor hygiene practices and, in preparing the family meal, she passes the bacteria in through the food, and so the family also ingests the bacteria.

Skip to 4 minutes and 2 seconds So looking at the factor of their sanitation system, and sometimes the way that in a lot parts of the world, there’s no toilet. Most of the time, even there’s no latrine. And the communities, the citizens sometimes goes to the bush to indiscriminately discharge their fecal droppings there. And in the course, it’s the spread of the bacteria.

Skip to 4 minutes and 46 seconds In Kenya, like in the rural where I come from, there are people who wash in the river, bathe in the river. Then still animals come and drink the same river. And maybe in the evening, the same people will come and draw water from the river. So I see a chance of contaminating this water source. And this can also increase the chances of cholera.

Skip to 5 minutes and 33 seconds There are some criteria which are not mentioned, in my opinion. First of all is income of people, and the degree of income of people can have a direct influence on the propagation of cholera. For example, the people with higher incomes, they have– they can make use of better foods. They can make use of private toilets in their house, and better sanitation and hygiene available, which the agents can be government and humankind, both of them. And then another factor can be job of people. For example, there are some people who are in touch with more people, like teachers, or more animals, like veterinarians or farmers. They are in more risk, so they can– it can affect them.

Skip to 6 minutes and 17 seconds And another thing, I’m not sure if it completely fits in the subject or not, but the degree of knowledge of people about the cholera. That is, agents can be government and people, both of them. And some things about like digestive system, where the digestive system is that can be– yeah, the people who have pets, maybe the pets could go and drink water from river or somewhere to be populated from somewhere, and then propagate this disease to people. And the family which are more crowded, with more children, the people who are living in more crowded communities, they’re in more risk because of the more people, and more people means there is the probability of people that are infected are higher.

Skip to 7 minutes and 34 seconds Now, what you see is that we can keep on adding and adding and adding elements. What we did is we identified actually only one agent, the human being, here. But we have a whole list of environments already, and we have drawn some lines indicating links between the agents and the environment. We can still add on. We could identify a second agent. For example, the media. The media, that could broadcast about cholera cases, and maybe then this system would change. If people become more aware because of the behavior of the media, they could change their behavior and not drink the water. Et cetera, et cetera. So we can go on for a little while to complete this model.

Skip to 8 minutes and 37 seconds However, it is not important that it becomes complete right now. What is more important is that you are seeing that with little knowledge about a process, you can actually already start to develop a simulation model in this way. You can say this is your conceptual model. And also, people might have other topics for their simulations. If you have some understanding of the process, what I suggest is think about the process. Identify agents, behaviour of agents, environments, interactions. And that is a very good starting point for building your model.

Designing an agent based simulation

In this step you will learn how to design an agent-based simulation.

In the video you see a classroom example of an exercise I often do with my face to face students. Such a session starts with what you already know about the process you want to simulate. This knowledge can come from your own experience or from a literature review you conducted.

The video starts with a short explanation of the assignment, followed by a reflection in which the students write down everything they find relevant for the simulation. They list all the elements that they associate with the process of cholera diffusion in Kumasi. Lots of elements come up during the discussion in the video. Students conduct this step individually. After a few minutes we construct a flowchart together on the whiteboard that is based on the input given by the students.

From the suggestions of the students we identify the agents, the environments and the links between them. Sometimes we refine this by listing attributes of agents. Attributes provide specific information about the agent for example the income level of a household agent.

In the Comments section below add one or two elements that you find important in this case. Please think of elements that are not mentioned in the video.

The example used in the video is for the cholera model but, the steps you will have to take are the same for any type of agent-based simulation model. You can follow these steps to construct a conceptual design for your own simulation model. When you want to give this a try, you can do so in the next step.

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Geohealth: Improving Public Health through Geographic Information

University of Twente

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