HIV & AIDS in the SugarScape

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WHAT IS IT?

This is a modified version of SugarScape, as presented in "Growing Artificial Societies" by Epstein and Axtell. I would credit the original creators of the SugarScape model for netlogo but I can't find a name to credit!

This variation of the SugarScape model introduces HIV and AIDS to the agent population. Pink agents are female, blue agents are male, purple agents are no longer reproductive, and agents in a reproduction cycle are yellow. HIV-positive agents are red and agents with AIDS are black.


HOW IT WORKS

Patches represent a toroidal world with "sugar" (representing wealth) deposited in two roughly circular regons or "hills" of increasing sugar density. Agents obey rules for harvesting sugar and reproducing, while the sugar patches obey a growback rule. See book for details.

A small percentage of the starting population are infected with AIDS and with HIV. Normal agent behavior for agents at sexual maturity is, at each turn, to find a sexually mature neighbor of the opposite sex and engage in intercourse. Should the agents have sufficient sugar wealth for reproduction, a reproductive event will also occur.

Agents with HIV have varying probabilities of infecting partners with HIV, and also of infecting offspring with HIV. At each time-step, HIV-positive agents' risk of developing AIDS increases. When an agent contracts AIDS, they start to show negative physiological consequences. At each time-step, their metabolism increases because more resources are required to keep the sick agents alive, and their vision decreases because the sick agents are manifesting physical degeneration as a result of the illness.


HOW TO USE IT

Set the number of initial agents with the slider bar and click "setup" to distribute the population randomly between the two sugar hill corners of the environment. Click "go" to initiate the viral infection in a random selection of the population and watch the illness spread! Click "go" again to stop the carnage. Click the "step" button to watch the infection spread by time-step.


EXTENDING THE MODEL

This is an extremely simplified model of HIV and AIDS. Many possible extensions include adding user controls for infection probabilities and other model variables, which would complicate the interface but make it more interesting to explore. Developments that could improve the model of actual disease spread include such factors as prophylactic use, medications, monogamy, and agent behaviors involving discrimination among intercourse partners based on health characteristics.


CREDITS AND REFERENCES

http://www.brook.edu/press/books/ARTIFSOC.HTM - credit also to the original authors of the netlogo SugarScape model.

HIV & AIDS in the SugarScape, 2006 model by Andrea Wiggins


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