turtles-own[ days-sick fatality ] globals[ step setup-population ] to setup ca ;; clear screen crt initial-population ;; create turtles set setup-population initial-population set step .175 setup-patches ask turtles [ set shape "person" set color green set size 1.5 set days-sick 0 ifelse who = 0 [ set color red;; make one turtle sick ] [ setxy random-xcor random-ycor ;; set random positions ] ] ifelse num-doctors < count(turtles) [ ;; make some of the turtles into doctors ask n-of num-doctors turtles with [color != red] [ set color white ] ] [ ;; if the number of doctors is more than the number of turtles, ;; make all the turtles doctors ask turtles [ set color white ] ] reset-ticks end to setup-patches ask patches[set pcolor black] if limit-travel ;; set up two borders dividing the screen [ let quarentine-x -10 ask patches [ if (pxcor) = quarentine-x [ set pcolor brown ] ] ask n-of travel-openings patches with [pxcor = quarentine-x] [ set pcolor black ] set quarentine-x 10 ask patches [ if (pxcor) = quarentine-x [ set pcolor brown ] ] ask n-of travel-openings patches with [pxcor = quarentine-x] [ set pcolor black ] ] end to go ask turtles [ move ;; move randomly get-infected ;; get infected deceased ;; could die recover if vaccination [ get-vaccinated ] if medication [ get-treated ] ] tick end to recover if color = red and days-sick > days-to-recover and random 100 < 20 [ ifelse (fatality = true) [ die ] [ set color blue ] ] end to move rt random 30 lt random 30 ifelse patch-ahead 1 != nobody and [pcolor] of patch-ahead 1 = black [ fd step ] [ rt 180 ] end to get-infected let hygiene-factor (1 - (hygiene * .009)) if color = green and any? turtles-here with [color = red] and random 100 < (infectiousness * hygiene-factor * step) [ set color red set fatality (random 100 < fatality-rate) ] end to get-vaccinated if color = green and any? turtles-here with [color = white] and random 100 < (100 * step) [ set color blue set shape "vaccinated" ] end to get-treated if color = red and any? turtles-here with [color = white] [ set color blue set shape "tamiflu" ] end to deceased if color = red [ set days-sick days-sick + step ] if color = red and fatality = true and random 100 < 30 [ die ] end @#$#@#$#@ GRAPHICS-WINDOW 384 10 924 551 26 25 10.0 1 10 1 1 1 0 0 0 1 -26 26 -25 25 1 1 1 ticks 30.0 BUTTON 34 102 122 135 Setup Model setup NIL 1 T OBSERVER NIL NIL NIL NIL 1 BUTTON 34 141 122 174 Run/Pause go T 1 T OBSERVER NIL NIL NIL NIL 1 SLIDER 12 506 193 539 fatality-rate fatality-rate 0 100 5 1 1 % HORIZONTAL MONITOR 84 180 156 225 Infected count(turtles with [color = red]) 17 1 11 PLOT 10 229 376 415 Populations NIL NIL 0.0 10.0 0.0 10.0 true true "" "" PENS "healthy" 1.0 0 -10899396 true "" "plot (count(turtles with [color = green]))" "sick" 1.0 0 -2674135 true "" "plot (count(turtles with [color = red]))" "immune" 1.0 0 -13345367 true "" "plot (count(turtles with [color = blue]))" "total" 1.0 0 -16777216 true "" "plot (count(turtles))" SWITCH 246 29 376 62 limit-travel limit-travel 0 1 -1000 MONITOR 240 181 303 226 Total count(turtles) 17 1 11 SLIDER 246 61 376 94 travel-openings travel-openings 0 10 3 1 1 NIL HORIZONTAL SLIDER 12 440 192 473 infectiousness infectiousness 0 100 30 1 1 % HORIZONTAL SLIDER 5 29 233 62 initial-population initial-population 0 2000 1500 1 1 NIL HORIZONTAL SLIDER 12 473 192 506 days-to-recover days-to-recover 0 100 14 1 1 days HORIZONTAL TEXTBOX 8 10 158 28 Initial Settings 14 0.0 1 TEXTBOX 15 420 165 438 Disease Parameters 14 0.0 1 MONITOR 10 180 77 225 Healthy count(turtles with [color = green]) 17 1 11 MONITOR 161 181 238 226 Immune count(turtles with [color = blue]) 17 1 11 SWITCH 163 145 271 178 vaccination vaccination 1 1 -1000 SLIDER 5 61 233 94 num-doctors num-doctors 0 10 0 1 1 NIL HORIZONTAL SWITCH 270 145 378 178 medication medication 1 1 -1000 MONITOR 304 507 375 552 Vaccinated count turtles with [shape = \"vaccinated\"] 17 1 11 MONITOR 304 462 379 507 Medicated count turtles with [shape = \"tamiflu\"] 17 1 11 MONITOR 304 417 375 462 Recovered count turtles with [color = blue and shape = \"person\"] 17 1 11 TEXTBOX 223 423 302 457 Immunity From: 14 0.0 1 MONITOR 305 181 375 226 Died setup-population - count(turtles) 17 1 11 TEXTBOX 170 96 352 116 Prevention and Treatment 14 0.0 1 SLIDER 163 112 378 145 hygiene hygiene 0 100 15 1 1 % HORIZONTAL @#$#@#$#@ ## WHAT IS IT? This model represents the spread of a disease in a population. It is meant to illustrate the various factors that can affect how quickly and how far a disease can spread. The people in this model can have various states representing their state. Here are the different states and the colors that indicate them: Susceptible (Healthy) - Green These people have not caught the disease yet and are susceptible to catch it. They are in danger of catching the disease if they meet an infected person. Infected - Red These people are infected with the disease and are contagious. They can pass the disease on if they meet a susceptible person. Immune - Blue These people cannot catch the disease. There are various reasons for an person to be immune: --- Recovered (plain blue): these people have caught the disease and recovered. --- Vaccinated (holding yellow shields): these people have been vaccinated by a doctor. --- Medicated (holding pill bottles): these people had the disease, but were treated by a doctor. Doctors - White Doctors are treated as immune to so that medical care will always be available to the population in the model. Doctors can give vaccinations and medication if the switches are turned on for those treatments. ## HOW IT WORKS As the people interact, if a susceptible person meets an infected person, there is a certain chance (indicated by infectiousness) that the disease will infect the susceptible person. Infected people can recover after a period of time (indicated by days-to-recover). A portion of them (indicated by fatality-rate) may die from the disease. The hygiene slider causes the infectiousness of the disease to take less effect. It can be compared to attempts to contain the disease wearing masks, using proper sanitation, or washing hands. People still inadvertently catch the disease, but the disease spreads a lot slower. In order to administer any treatments, you must add doctors before initializing the model. If vaccination is on, the doctors will vaccinate any susceptible people they encounter. If medication is on, the doctors will treat any infected people they encounter. The limit-travel setting is meant to represent different countries or regions that may limit travel in an attempt to contain the disease. Less openings represent tighter regulations on travel. ## HOW TO USE IT Initializing the Model: - Use the switches and sliders to set your desired initial settings: --- initial-population determines how many people will be in the model at the beginning --- num-doctors determines the how many people will be doctors --- limit-travel determines whether to add barriers between different regions of the "world" --- travel-openings determines how many gaps there will be in the barriers - Click Setup Model. You should see people appear in the black "world." Running the Model: - To start the model, click Run/Pause. - To pause the model, click Run/Pause again. - To re-initialize the model with your current settings, click Setup Model again. - You can speed up and slow down the model using the slider on the top of the "world." Adding Prevention and Treatment: - In order to administer vaccination and medication, you must add doctors before initializing the model. - You can use these sliders to try different methods to keep the disease from spreading. These settings can be changed while the model is running. --- hygiene determines how much infected people use measures such as hand-washing and covering their mouths when sneezing and coughing --- vaccination will allow the doctors to vaccinate susceptible people when it is turned on --- medication will allow the doctors to administer medication that will help infected people to recover Modifying the Disease: - If you want to change nature of the disease, you can use the sliders below the graph. These settings can be changed while the model is running. --- infectiousness determines how contagious the disease is --- days-to-recover determines how quickly people will get better and become immune --- fatality-rate determines how likely a person is to die from the disease ## THINGS TO TRY How does population density affect the spread of a disease? --- Set the initial population to 2000 people. Run the model a few times. Record the number of people who are recovered and the number of people who died when the infection stops spreading. Why is an epidemic especially dangerous in a crowded city like New York? --- Try again with about 1500, 1000, and 500 people. Record the number of people who are recovered and the number of people who died when the infection stops spreading. Density as a factor. A disease can spread more quickly the denser a population is. How does a quarantine help to stop the spread of an infection? When is it appropriate to enforce a quarantine? What can be some of the ethical problems with quarantining individuals? --- Run the model a few times with no limitations on travel. Next, try different numbers of openings. Observe the results when different regions close themselves off. In particular, you may see a second peak in the number of infected people on the graph if the infection breaks out into one of the adjacent regions. ## EXTENDING THE MODEL Using measurements and observations from real disease data, this model could be changed to depict a particular disease. ## RELATED MODELS These are related models in the NetLogo Model Library: Disease Solo Virus ## CREDITS AND REFERENCES Built by Valerie Gartland for Shodor http://www.shodor.org @#$#@#$#@ default true 0 Polygon -7500403 true true 150 5 40 250 150 205 260 250 airplane true 0 Polygon -7500403 true true 150 0 135 15 120 60 120 105 15 165 15 195 120 180 135 240 105 270 120 285 150 270 180 285 210 270 165 240 180 180 285 195 285 165 180 105 180 60 165 15 arrow true 0 Polygon -7500403 true true 150 0 0 150 105 150 105 293 195 293 195 150 300 150 box false 0 Polygon -7500403 true true 150 285 285 225 285 75 150 135 Polygon -7500403 true true 150 135 15 75 150 15 285 75 Polygon -7500403 true true 15 75 15 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