COVID19-variable-SD-Testing
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WHAT IS IT?
This is an extension of the model “Effects of testing and social distancing on the spread of infectious diseases ("Flattening the Curve")” by Shikhara Bhat http://modelingcommons.org/browse/one_model/6238#model_tabs_browse_info
This is a model to describe the effect of social distancing (SD) and testing on the spread of an infectious disease, using the SIRS model for spread of infectious diseases.
HOW IT WORKS
At the beginning of the model, a certain number of people in the population (controlled by the parameter NUMBER _ SICK) are INFECTED (shown in red), and the rest are SUSCEPTIBLE to infection (shown in green). This infection spreads according to the rules described below. The model stops once either everybody is infected, or nobody is infected (i.e the infection has 'died out')
Infection (the SIRS model)
A SUSCEPTIBLE person can acquire the disease from an INFECTED with probability TRANSMISSIBILITY, if they are within MAX _ INF _ RADIUS of that person.
All INFECTED have the potential to recover from the disease after time INFECTION _ PERIOD has passed. Once this time has passed, an INFECTED individual becomes a RECOVERED individual (shown in blue) with probability RECOVERY _ RATE.
RECOVERED individuals cannot acquire the infection. Every RECOVERED individual has the potential to lose their immunity, and become SUSCEPTIBLE again, with probability SUSCEPTIBILITY.
Social Distancing (SD)
A percentage of the individuals, determined by PERCENTAGESD, is assigned an exclusion radius or SDradius obtained from a DISTRISD (Uniform, Normal or Poisson) radius distribution, with mean value SDMean. If MovementType= “MetropolisT=0”, the individuals move to a new position only if there isn't another individual within a distance of its own exclusion radius, and do not move otherwise. If MovementType= “awayfrommean”, individuals move away from their location if there are any other individuals within a distance of its own exclusion radius from them, and do not move otherwise. Individuals with no exclusion radius assigned, move randomly in either MovementType configuration.
Testing
A random sample (of size NUM _ TO _ TEST) of the population is tested for the disease at regular intervals (A test is conducted once every TEST _ PERIOD ticks). If an individual is found to be infected, they are removed from the population (This represents quarantine).
HOW TO USE IT
Set a random SEED, to make sure that the runs both begin with the same initial positions and statuses of the agents. Press SETUP to set the model with the initial conditions you have chosen (on the sliders), and press GO to run the model. Press CLEAR PLOT to clear the plot of all graphs, if the view gets too cluttered
Set a random SEED, to make sure that the runs both begin with the same initial positions and statuses of the agents. With NUMEXPERIMENTS one can set a number of different runs to get statistical averages. Press SETUP to set the model with the initial conditions you have chosen (on the sliders), and press GOEXPERIMENTS to run the model. Press CLEAR PLOT to clear the plot of all graphs, if the view gets too cluttered
Two OUTPUT files will be generated: LAMMPSFILE and OUTPUTFILE. The names of these files can be changed in the corresponding text boxes of the interface. The first file is a DUMMP file to be read by graphical softwares such as Ovito to produce movies or snapshots. This file saves the coordinates, type(Infected, Susceptible, Recovered) and SDradius of all individuals every FREQDUMP_FILE ticks. The second output file is a .dat file containing the average infected individuals over time and the standard deviation of the average values.
THINGS TO NOTICE
Social distancing 'flattens the curve'. In the real world, this means that the rate of infection is lower, greatly decreasing the burden on healthcare professionals and medical institutions, and thus lowering overall death rates. This is why social distancing is so important in the event of an epidemic/pandemic. Additionally, effective testing (either large number of individuals being tested at each step, or more tests being conducted in the same amount of time) can also flatten the curve.
THINGS TO TRY
Change the ratio of MIN _ SD _ RADIUS to MIN _ INF _ RADIUS to see how this affects the effectiveness of social distancing. In real world terms, this could be seen as a measure of HOW MUCH distance (not necessarily simply physical) you need to maintain for social distancing to be effective.
Try changing the MOVEMENT_TYPE to see how these rules affect the dynamics and the final results. Try changing the distributions of the SD to see how this modifies the flattening of the curve. Specially, compare UNIFORM distribution to others to see the effect of not all individuals having the same amount of SD.
EXTENDING THE MODEL
Suppose quarantined individuals aren't permanently removed but are instead 're-inserted' into the population as healthy individuals once the infection period has passed. How does this affect dynamics? Suppose individuals in the population can reproduce and die of old age (or die due to the disease itself). How is the model affected by this?
RELATED MODELS
“Effects of testing and social distancing on the spread of infectious diseases ("Flattening the Curve") “, by Shikhara Bhat (Author) .
http://modelingcommons.org/browse/one_model/6238#model_tabs_browse_info
The AIDS model (in the Biology section of the standard NetLogo models).
CREDITS AND REFERENCES
SIR model: Kermack, W; McKendrick, A (1991). "Contributions to the mathematical theory of epidemics—I". Bulletin of Mathematical Biology. 53 (1–2): 33–55. doi:10.1007/BF02464423
Comments and Questions
;------------------------------------------------------------------------------------------------------------------- ; ; ; ; percentage_SD: % of agents who keep SD ; ; SD_mean, SD_sigma: mean value and variance of SD (normal distribution) ; ; movement_type: "away from mean" o "metropolis T=0" ; ; test_period: ticks between tests ; ; num_to_test: number of tests performed each test_period ticks ; ; max_inf_radius: maximum radius of infection ; transmissibility: probability of becoming infected when there is a patient less than max_inf_radius ; ; ;------------------------------------------------------------------------------------------------------------------- extensions [array] ; to use arrays globals [acum acum2 sigma n_experiments t s1 s2] breed [infecteds infected] breed [susceptibles susceptible] breed [recovereds recovered] infecteds-own [ clock tested? ] turtles-own [ neighbours keep_SD SD_own xcor_old ycor_old ] ;------------------------------------------------------------------------------------------------------------------- ; General setup and setup to restart an experiment ;------------------------------------------------------------------------------------------------------------------- to setup set acum array:from-list n-values t_max [0] ; fill the array with zeros set acum2 array:from-list n-values t_max [0] set sigma array:from-list n-values t_max [0] set n_experiments 1 ; set number of experiments initially to zero setup-experiment let LX ( max-pxcor * 2 + 1) let LY ( max-pycor * 2 + 1) clear-output output-print "DENSITY:" output-write (number / (LX * LY)) output-print " agents/m2" output-write ((LX * LY) / number) output-print " m2/agent" output-write sqrt ((LX * LY) / number) output-print " average distance" end ; setup for a new experiment to setup-experiment clear-turtles clear-ticks random-seed new-seed ; to start each simulation with a different seed create-turtles number [setxy random-xcor random-ycor set size 1 set keep_SD ((random-float 1) < (percentage_SD / 100.0)) ; is a fixed attribute of each agent (ifelse distri_SD = "uniforme" [ set SD_own SD_mean ] distri_SD = "normal" [ set SD_own random-normal SD_mean SD_sigma if (SD_own < 0 ) [set SD_own 0 ] ] distri_SD = "poisson" [ set SD_own random-poisson SD_mean ]) ifelse (who < number_sick_initial) [set breed infecteds set clock 0 set tested? False] [set breed susceptibles] recolor ] reset-ticks file-close ;cierra el lammps_file if file-exists? lammps_file [ file-delete lammps_file ] file-open lammps_file end to recolor if (breed = susceptibles) [ set color green ] if (breed = infecteds) [ ifelse (tested? = True) [set color white] [set color red] ] if (breed = recovereds) [ set color blue ] end ;------------------------------------------------------------------------------------------------------------------- ; move ;------------------------------------------------------------------------------------------------------------------- to move [dist] ifelse(keep_SD) ; that an agent save SD is an attribute that is defined in setup with some probability [ ; aqui guarda SD... (ifelse movement_type = "metropolis T=0" [ ; type of Metropolis movement at temperature 0 (move-count-accept-reject) set xcor_old xcor set ycor_old ycor rt random-float 360 fd dist if (count(other turtles in-radius SD_own) >= 1 ) [ set xcor xcor_old set ycor ycor_old ] ] movement_type = "away from mean" [ ; type of movement runs away from the center of mass of neighbors (counts-turns 180-moves) set neighbours other turtles in-radius SD_own if (count(neighbours) >= 1) ;Move only if you have neighbours [ facexy (mean [xcor] of neighbours) (mean [ycor] of neighbours) rt 180 ; Turn away from the mean x and y co_ordinates of your neighbours fd dist ] ] [ error 111 ]) ] [ ; random walk... rt random-float 360 ;Turn to a random direction fd dist ] end to get_infected ;S _> I let sick_neighbours infecteds in-radius max_inf_radius if (breed = susceptibles and count sick_neighbours >= 1) [if ((random-float 1) < (1 - ((1 - transmissibility_rate)^(count(sick_neighbours))))) [set breed infecteds set clock 0 set tested? False] ] end to recover ;I _> R if (clock >= infection_period and (random-float 1 < recovery_rate)) [set breed recovereds] end to lose_immunity ;R _> S if (random-float 1 < lose_immunity_rate) [set breed susceptibles] end to advance_clock ;For recovery of infected people set clock (clock + 1) end to runtest if (breed = infecteds) [die] end to test; ifelse (num_to_test <= count(turtles)) [let testsubjects n-of num_to_test turtles ask (testsubjects) [runtest]] [ask (turtles) [runtest]] end ;------------------------------------------------------------------------------------------------------------------- ; go to do various experiments and average ;------------------------------------------------------------------------------------------------------------------- to go-experiments go if (count(infecteds) = 0 or count(infecteds) = count(turtles) or ticks > t_max) ;Stop if nobody is infected, or everybody is infected [ ; if you enter here start a new experiment if (n_experiments = num_experiments) [ file-close ;cierra el lammps_file if file-exists? output_file [ file-delete output_file ] file-open output_file file-print "# t infecteds error" set t 0 while [t < t_max] [ set s1 array:item acum t set s2 array:item acum2 t array:set sigma t sqrt ( s2 / num_experiments - ( (s1 / num_experiments) ^ 2 ) ) file-write t file-write ( s1 / num_experiments ) file-write ( ( array:item sigma t ) / sqrt(num_experiments ) ) file-print "" set t (t + 1) ] file-close stop ] set n_experiments (n_experiments + 1) setup-experiment ] end to lammps file-print "ITEM: TIMESTEP" file-print ticks file-print "ITEM: NUMBER OF ATOMS" file-print count turtles file-print "ITEM: BOX BOUNDS xx yy zz" file-write min-pxcor file-type " " file-print max-pxcor file-write min-pycor file-type " " file-print max-pycor file-print "0.0 0.0" file-print "ITEM: ATOMS id type x y z radius" ask (recovereds) [ file-write who file-write 1 file-type " " file-write xcor file-type " " file-write ycor file-type " " file-write 0.0 file-type " " file-print SD_own ] ask (susceptibles) [ file-write who file-write 2 file-type " " file-write xcor file-type " " file-write ycor file-type " " file-write 0.0 file-type " " file-print SD_own ] ask (infecteds) [ file-write who file-write 3 file-type " " file-write xcor file-type " " file-write ycor file-type " " file-write 0.0 file-type " " file-print SD_own ] end ; go of an experiment to go if (ticks mod freq_dump_file = 0) [lammps] ask (recovereds) [lose_immunity] ask (susceptibles) [get_infected] ask (infecteds) [advance_clock] ask (infecteds) [recover] ask (turtles) [move 1] ask (turtles) [recolor] if (ticks mod test_period = 0) [test] if ticks < t_max [ array:set acum ticks ( array:item acum ticks + (100 * count(infecteds) / count(turtles) ) ) array:set acum2 ticks ( array:item acum2 ticks + ((100 * count(infecteds) / count(turtles)) ^ 2) ) set s1 array:item acum ticks set s2 array:item acum2 ticks array:set sigma ticks sqrt ( s2 / n_experiments - ( (s1 / n_experiments) ^ 2 ) ) ] tick end
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File | Type | Description | Last updated | |
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COVID19-variable-SD-Testing.png | preview | Preview for 'COVID19-variable-SD-Testing' | over 5 years ago, by Eduardo Bringa | Download |
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Eduardo Bringa
Ancestors and extensions
This is an extension of the model “Effects of testing and social distancing on the spread of infectious diseases ("Flattening the Curve")” by Shikhara Bhat. http://modelingcommons.org/browse/one_model/6238 Includes variable Social Distance and different types of agent motion. Also includes output with agent position and type.
Posted over 5 years ago
Eduardo Bringa
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detailed Model Info can be found by using "Run in NetLogo" and then clicking on "Model Info" at the bottom. Running in NetLogo Web is not yet possible, and we are working to solve this issue as soon as possible.
Posted over 5 years ago
Eduardo Bringa
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Posted over 5 years ago