1. Epidemic Modeling in NetLogo Brendan Greenley Pd. 3

2. Purpose Create a simple yet realistic model of an epidemic Create a simple yet realistic model of an epidemic Figure out how manipulating variables changes the behavior of an epidemic. Figure out how manipulating variables changes the behavior of an epidemic.

3. Goals Identify how changes in variables such as death rate, virus duration, and time until quarantine affect the behavior/duration of an epidemic Identify how changes in variables such as death rate, virus duration, and time until quarantine affect the behavior/duration of an epidemic Allow for simple tweaking of variable through sliders Allow for simple tweaking of variable through sliders Implement System Dynamics (SD) Implement System Dynamics (SD)

4. Program Run Run time possibilities Run time possibilities Short term (one epidemic)Short term (one epidemic) Long term (reoccurring epidemics)Long term (reoccurring epidemics) Key End Results Key End Results Death countDeath count Length of outbreakLength of outbreak Time with maximum # of infectionsTime with maximum # of infections Results shown graphically (real-time) Results shown graphically (real-time)

5. Similar Projects Numerous epidemic models Numerous epidemic models None implement System Dynamics None implement System Dynamics More complex More complex ParametricsParametrics DifferentialsDifferentials Basic assumptions frequently the same Basic assumptions frequently the same Infections can only spread from sick -> unaffectedInfections can only spread from sick -> unaffected Those who survive gain immunity (unless virus mutates)Those who survive gain immunity (unless virus mutates) Those infected but quarantined cannot spread virusThose infected but quarantined cannot spread virus

6. NetLogo Programming language (Northwestern) Programming language (Northwestern) More popularly used in multi-agent based programming More popularly used in multi-agent based programming My use: System Dynamics My use: System Dynamics Crossplatform support Crossplatform support Windows, *Nix, MacWindows, *Nix, Mac Free! Free!

7. Procedure Add stock/flows in smaller groups Add stock/flows in smaller groups Check to see if smaller, simpler linkages work properly by tracking stock populations in test runs Check to see if smaller, simpler linkages work properly by tracking stock populations in test runs Attempt to link smaller linkages into one greater system Attempt to link smaller linkages into one greater system Check with a test run and repeat until project has one, huge working system of flows. Check with a test run and repeat until project has one, huge working system of flows.

8. Time Line First quarter: First quarter: Learn how to use NetLogoLearn how to use NetLogo Experiment with non-SD proceduresExperiment with non-SD procedures Second Second Successfully create a basic model that encompasses unaffected, infected, quarantined, and immune stocksSuccessfully create a basic model that encompasses unaffected, infected, quarantined, and immune stocks Third Third Add more variables and flows to modelAdd more variables and flows to model Attempt to have epidemics repeat over a longer period of time (centuries), with different variations and mutations expressed by a change in variablesAttempt to have epidemics repeat over a longer period of time (centuries), with different variations and mutations expressed by a change in variables Fourth Fourth Focus on data collection and make conclusions from data, look at derivatives of graphs, etc.Focus on data collection and make conclusions from data, look at derivatives of graphs, etc.

9. Problems Changing rates over time Changing rates over time As awareness of disease increases, so should quarantine rateAs awareness of disease increases, so should quarantine rate Using flows realistically Using flows realistically Balancing population shifts with eachotherBalancing population shifts with eachother Combining System Dynamics and non-SD components can be difficult Combining System Dynamics and non-SD components can be difficult Ticks Ticks Should a tick represent a day? An hour?Should a tick represent a day? An hour?

10. Post-development Possibilities What if I finish early… What if I finish early… Try to create same model in NetLogo, but without using System DynamicsTry to create same model in NetLogo, but without using System Dynamics Extend my epidemic model so it can be used to model long term diseases like HIV/AIDSExtend my epidemic model so it can be used to model long term diseases like HIV/AIDS Agents to represent the populations and have them shown on a GUIAgents to represent the populations and have them shown on a GUI

11. Results Due to natural immunities, killing off an entire population in one epidemic is difficult. Due to natural immunities, killing off an entire population in one epidemic is difficult. Viruses that are too deadly are poor diseases, they quickly die off. Viruses that are too deadly are poor diseases, they quickly die off. Quarantining is a very effective measure to slow the infection rate. Quarantining is a very effective measure to slow the infection rate. My SD model yields smoother curves than my non-SD model, (though there are slightly different algorithms/values used) My SD model yields smoother curves than my non-SD model, (though there are slightly different algorithms/values used)

12. System Dynamics Model

13. Non-System Dynamics Model

14. Plan Changes I shifted away from System Dynamics, but came back to it I shifted away from System Dynamics, but came back to it SD environment yields less mistakes; fewer chances for typos/forgetting to update variables than non-SD NetLogo SD environment yields less mistakes; fewer chances for typos/forgetting to update variables than non-SD NetLogo I initially was going to do agent based modeling, but that is difficult to do with System Dynamics. I initially was going to do agent based modeling, but that is difficult to do with System Dynamics.