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Initializing Disease Compartments

When a certain disease model should be used in scenario, the initial conditions for the isease have to be specified. The following components in STEM enable the user to do so. The Disease Initializer component provides the combined functionality of the Infector and Inoculator components. For initialization from an external file the External Data Source Disease Initializer must be used.

Infector

InnoculatorWiz.png

Please see Creating a STEM Scenario to see an example of how infectors are used. Infectors can be used to set initial conditions when you want to start a simulation with a specific number or percentage of people in the infectious state. The infector, at simulation start, takes the specified number from the Susceptible state and moves them to the infectious state. You can configure an inoculator to set the initial condition for a specific regions, at node containing sub-regions (e.g., a state or country) or your entire graph. The wizard for creating an infector is shown to the right.

Inoculator

Inoculators are very similar to infectors. They are used to set the initial condition or initial state of a population when a user wants to set the herd immunity at simulation start. They work by moving a specified number or percentage of people from Susceptible to Recovered. Like infectors you can configure an inoculator to set the initial condition for a specific regions, at node containing sub-regions (e.g., a state or country) or your entire graph.


Disease Initializer

Disease Initializers are a much more flexible and powerful way to set initial conditions. Users can specify and set or target compartments to initialize so a Disease Initializer can play the role of Infector, Inoculator, and more. For example one can also set the initial number of Exposed people in an SEIR model. To create an initializer for a specific disease, the user has to right click on the disease and select "Create new Initializer".

StemCreateInitializer.png

Since initializers also work for diseases with multiple populations, the population to initialize has to be selected. For the selected population the absolute number or percentage of individuals for all compartments can be specified. At last the user has to select a location for the initializer. If for example France is selected, any region in France is initialized with the chosen values. The new initializer will show up under the "Decorators" folder in the Project explorer. You can drag the initializer right into a scenario.

StemInitializer.png

External Data Source Disease Initializer

To create an initializer for a specific disease, the user has to right click on the disease and select "Create new External Data Initializer".

StemCreateDataInitializer.png

Since initializers also work for diseases with multiple populations, the population to initialize has to be selected. For the selected population the folder containing the log files for the specific disease and population has to be entered. Finally one must specify the number of the row to be used. The new initializer will show up under the "Decorators" folder in the Project explorer. You can drag the initializer right into a scenario.

StemDataInitializer.png