Infection Dynamics - Practice

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WHAT IS IT?

This simulation helps explore how an infection spreads, recovers, reinfects, and how doctors and hospitals can influence the outcome. It is designed as a self-learning tool for understanding real-world infection dynamics and system behavior.

HOW IT WORKS

In this simulation, a small population of turtles moves around a virtual world, where the spread of infection plays out dynamically. At the start, most turtles are healthy (blue), but a few begin infected (red). As they move, infected turtles can transmit the illness to nearby healthy ones. Some infected turtles are programmed to seek care in a designated hospital area, marked with a large pink “H.” However, hospital capacity is limited, so only a few can be treated at a time. Once inside, turtles stay locked in until they recover, which happens faster than in the outside environment.

Doctors, colored orange and labeled “Doctor,” roam the world searching for infected turtles. When they find one within range, they administer care that helps the turtle recover and turn green. Recovered turtles are not immune forever — after some time, they may lose immunity, flash cyan with a “Lost Immunity” label, and become susceptible to infection again.

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NETLOGO FEATURES

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RELATED MODELS

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globals [
  trail_count
  total_infected
  max_infected
  total_healed_by_doctors
  hospital_capacity
]

turtles-own [
  infected_time
  recovered_time
  reinfected?
  reinfected_for
  in_hospital_lock?
  will_go_to_hospital?
]


breed [doctors doctor]

to-report in_hospital?
  report [pcolor] of patch-here  = pink
end 

to setup
  clear-all
  set trail_count 0
  set total_infected 1
  set max_infected 1
  set total_healed_by_doctors 0
  set hospital_capacity 5


  ask patches [ set pcolor blue + 4.9]

   ; set hospital zone
  ask patches with [ pxcor > max-pxcor - 5 and pycor > max-pycor - 5]
  [set pcolor pink
  ]

  ; Mark hospital area with a big H

  ask patches with [
    pxcor > max-pxcor - 3 and pxcor < max-pxcor - 1 and
    pycor > max-pycor - 3 and pycor < max-pycor - 1
  ]
  [ set plabel "H"
    set plabel-color black
  ]





  create-turtles 30 [
    setxy random-xcor random-ycor
    set color blue
    set infected_time 0
    set recovered_time 0
    set reinfected? false
    set reinfected_for 0
    set in_hospital_lock? false
    set will_go_to_hospital? false
  ]

  ask n-of 5 turtles [
    set color red
    set infected_time 1
  ]

  create-doctors 2 [
    setxy random-xcor random-ycor
    set color orange + 1
    set size 1.3
    set label "Doctor"
    set label-color black
  ]

    reset-ticks
end 

to go
  ;main turtle logic
  ask turtles with [not member? self doctors ] [

    ;infection logic
    if color = red [
      let nearby-turtles turtles in-radius 1 with [color = blue]
      ask nearby-turtles [
        set color red
        set infected_time 0
        set total_infected total_infected + 1
        set will_go_to_hospital? (random-float 1.0 < 0.2)
      ]
    ]

    ;Recovery logic

    set infected_time infected_time + 1

    if in_hospital? [
      set infected_time infected_time + 2
    ] ; faster recovery in hospital

    if infected_time > recovery_time and color = red [
      set color green
      set recovered_time 0
      set in_hospital_lock? false
     ]





    ;Reinfection logic

    if color = green [
        set recovered_time recovered_time + 1

        if recovered_time > reinfection_delay and not reinfected? [
         set color cyan ; flash color to highlight reinfection
         set label "Lost Immunity"  ; showing label
         set label-color black
         set reinfected? true
         set reinfected_for 25 ; flash will last for 25 ticks
         set size 2 ; make the turtle stand out
        ]
    ]

    ; maintain flash for a few ticks
    if reinfected? and reinfected_for > 0 [
      set reinfected_for reinfected_for - 1
    ]

    ; end flash, reset to blue

    if reinfected? and reinfected_for = 0 [
      set color blue
      set infected_time 0
      set label ""
      set reinfected? false
      set size 1 ; reset to previous size
        ]

    ; hospital entry logic

    if color = red and will_go_to_hospital? and not in_hospital? and not in_hospital_lock? [
      if xcor = max-pxcor - 5 and ycor >= max-pycor - 5 [
        if count turtles with [ color = red and in_hospital_lock? ] < hospital_capacity [
          facexy max-pxcor - 3 max-pycor - 3
          forward 1
        ]
      ]
    ]


    ; lock turtle when it get inside hospital
    if color = red and in_hospital?  and will_go_to_hospital? and not in_hospital_lock? [
      if count turtles with [color = red and in_hospital_lock?] < hospital_capacity [
      set in_hospital_lock? true
    ]
    ]

    ; lock movement if inside hospital and infected

     if in_hospital_lock? [
      if not in_hospital? [
        facexy max-pxcor - 3 max-pycor - 3
        forward 1
      ]
    ]


    ; block healthy turtles from entering hospital

    if (color != red and in_hospital?)  [
      rt 180
      forward 1
    ]



    ;movement logic

    forward movement_speed
    rt random 50
    lt random 50



    if color = green and in_hospital? [
  rt 180
  forward 1
    ]
  ]




  ;update max infected count
  let current_infected count turtles with [color = red ]
    if current_infected > max_infected [
      set max_infected current_infected
    ]

  ; Doctors logic
  ask doctors [
    let nearby_infected turtles in-radius 1 with [color = red]
    ask nearby_infected [
      set color green
      set total_healed_by_doctors total_healed_by_doctors + 1
    ]

 ; doctor movement
  forward 1
  rt random 30
  lt random 30
]


  tick
end

There is only one version of this model, created 2 months ago by Mohammad Mustafa.

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