Model Description

On the Model page of this web site is a very simple agent-based model that shows the potential spatial dynamics of disease spread. Because the model is spatial, it could also be referred to as a Spatially Explicit Individually Based Model or SEIBM.

Using the Model

The easiest way to use the model is to just press "Start". The model will run and you will see the agents moving around on the area to the right. Also, a graph will appear below the controls that show the number of living and uninfected individuals. When you click "Infect", you will infect one random individual in the population which will be then colored red. The disease will then spread based on the settings of the controls. When the infected individuals reach the "Max Infection Level", they will either die (crosses) or recover (blue). The chart shows living, uninfected individuals in green, infected individuals in red and dead individuals in black.

You can "Stop" the model at any time and then press "Go" to continue. You can also press "Start" which will restart the model.

Setup Controls

The first set of controls on the left setup the area for the model. These are used to create the area and the agents when you press "Start".

• Cell Size in Pixels - the agents in the model move around a grid of cells. This value determines the size of those cells.
• Grid Width - the number of cells horizontally. Change this value and the "Grid Height" to have the model match the area on your screen.
• Grid Height - the number of cells vertically
• Number of Agents - the total number of agents to start with. Try different values here to see how diseases change their rate of spread based on population density.

Dynamic Controls

These controls change the behavior of the model while it is running.

• Transmission Distance - the distance, in cells that the disease will propagate to a new individual. Change this value to see how diseases that are airborne spread vs. ones that require human contact.
• Max Move Distance - the maximum distance that any individual will move in one cycle. Change this value to see how traveling impacts the spread of disease
• Attraction - 0 provides no attraction or repulsion while a negative value will make individuals included to spread out and a positive value will make them group together.
• Max Infection Level - this represents the time it takes to either recover or die from the disease. Change the value to see how diseases that are quick do not spread as much as those that last a long time.
• Death Rate - the proportion of individuals that die vs. recover from the disease.