Version 0: basic epidemic model with population, recovery, and transmission sliders.
Version 1: Data boxes for transmission and recovery. Once recovered, turtles turn white and are immune.
Version 4: No mitigation, 500 healthy & 7 infected, immune after recovery. @ 150 everyone is immune. Model stops when the system is healed (no more infected turtles).
Current: final epidemic behavior with no mitigation. Healthy until collision or w/in 3 steps of infected. Remain infected for 14-42 days, then either die or go through 14-42 days of immunity followed by a return to healthy w possibility of reinfection.