Smallpox Martyr Bio-Terrorism ScenarioModeling

Computer Systems Lab 2009-2010

Joe Fetsch

January 27, 2010

Abstract

This project is intendedto model a martyr-type sce-nario in which a small ter-rorist group infiltrates acity after infecting them-selves with a weaponized,vaccine-resistant strain ofVariola major; agents ofthe group attack hospitalsfirst, passing as flu suffer-ers until they become con-tagious. After panic be-gins to spread, as the pop-ulation realizes that theywould have to avoid med-ical facilities even if theybecome infected, the re-maining faction infiltratesthe city, spreading the virusfurther. With the masspanic and disease spread-ing, the city shuts down.Nobody is allowed in orout, effectively quarantin-

ing the city. Residentspanic and remain at homein fear of infection, at whichpoint the city stops func-tioning completely as in-fections spread and diseasecontrol units are helpless tointervene due to the quar-antine and the population’sgeneral panic. After sometime, control of the city isregained as quarantine isimplemented, or a new vac-cine to counter the modifiedstrain of smallpox is devel-oped, mass produced, anddistributed en masse. Af-ter this point, the dangerfrom the attack drops tozero as the remaining sur-vivors have nothing else tofear from the now obsoletevirus weapon.

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1 Introduction

1.1 Actual Situation

If smallpox, or Variola, was releasedinto a population, the result would bea global spread and the virus wouldcause hundreds of thousands or evenmillions of fatalities. The long incu-bation time of smallpox would makespreading the disease from one townto another or from one country to an-other extremely common. Smallpoxcannot be aimed or targeted; oncereleased, it will kill and infect in-discriminately. This means that thegroup releasing the disease would alsoharm their own families, friends, andallies. Despite these dangers, thereare factions whose goal is only tocause panic at any cost, and oncethese groups have successfully ob-tained smallpox they pose a greatthreat to the rest of the world.”Although declared stocks of small-pox virus exist only at the two WorldHealth Organization repositories (theCenters for Dis- ease Control and Pre-vention [CDC] in Atlanta, Georgia,USA, and at the State Research Cen-ter of Virology and Biotechnology,also known as Vector, in Koltsovo,Russia), it is of concern that unde-clared stocks may exist in militarysites within the former Soviet Union,or that they were transferred from theSoviet program to programs in Iraq,Iran, North Korea, or elsewhere. The

probability that such stocks exist isimpossible to assess, but the catas-trophic consequences of smallpox re-lease in a biological attack cannotbe discounted.” (Jahrling, Huggins,Ibrahim, Lawler, and Martin 220)

1.2 Scenario

The scenario I am modeling is notconsidered in ”Smallpox and its Erad-ication;” the conclusion of the pas-sage involving a biowarfare attackusing smallpox states that an attackwould be unlikely (Fenner, Hender-son, Arita, Je?ek, and Ladnyi 1344).However, this conclusion was made inthe days after the eradication, beforebioengineering was as easy and possi-ble as it has become in recent years,and before terrorist groups, willingto sacrifice lives without strict regardfor whose lives were being sacrificed,were known to hold any significantpower in the modern stage. My sce-nario considers a vaccine-resistantstrain and a well-planned, indepen-dent attack by a small group of ter-rorist extremists; the danger fromthis threat has greatly increased inrecent years. According to Sderblom,this case is surprisingly likely and hasthe potential to kill millions of peopleor more around the world.

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1.2.1 Chance of an Attack

”Intelligence agencies and interna-tional relations scholars are con-cerned that Russian researchers of theformer Biopreparat, many whom areunemployed since the 1990s, and feeldisenfranchised, could be tempted tosmuggle and sell smallpox to thoseterrorist groups with the financial re-sources and microbiological expertiseto use it, or further weaponize it.Marvin Cetron, president of Fore-casting International Ltd, a risk as-sessment company working with boththe US Defense Department and theFBI, has stated, ”I think the chance isabout eighty percent of terrorists ob-taining smallpox...” Thereby, in theopinion of? experts, the potential fora serious smallpox attack is frighten-ingly feasible.” (Sderblom 3)

1.2.2 Execution of Attack

”In this scenario, two ”smallpox in-fected suicide terrorists” strategicallytarget doctors’ offices (in winter) toobtain a medical certificate to explaintheir absence from work. (They couldeven leave before seeing the physi-cian). They blend in with peoplesuffering flu symptoms in the wait-ing room, but they are already ef-fectively spreading smallpox amongststaff and patients. A terrorist orga-nization claims responsibility for the

outbreak. Citizens are too terrifiedto seek medical attention, as theyare now aware that medical facilitieshave been targeted. This is when thesecond stage of the bio-terror attackoccurs. Smallpox is delivered to thetarget city through either aerosolizeddelivery, or through another infectedset of suicide terrorists passing onsmallpox through exhaled droplets.Mass terror is created by the paradoxthat smallpox needs to be containedand treated, yet the mass smallpoxinfection of patients and staff at hos-pitals causes citizens to stay awayfrom medical facilities. A radio-talk-back host ponders on-air whether byattending the doctor to get checkedfor the flu, or vaccinated for small-pox, you may acquire... smallpoxbefore the vaccination takes effect.Large segments of the communityavoid medical treatment. The strainplaced on the infrastructure of thecity brings it to a halt: planes donot arrive or leave, police at road-blocks turn back fleeing residents,and the ”terror” caused by the bio-terror attack is unmatched by anypreviously experienced health catas-trophe. The economy is bought to astandstill and the bio-terrorists nowhave political influence as they havedemonstrated their capacity to inflictterror. Worse still, a rumor circulatesthat the smallpox is a weaponizedvariant from the former USSR, forwhich there is no vaccine. Thus the

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containment of infected people provesto be impossible even though WHOvaccines arrive quickly” (Sderblom 8-9).

1.2.3 Reaction to Attack

My simulation assumes that as theattacked population would panic, asSderblum stated, and, as the city shutdown, chaos would spread. The ter-ror caused by the attack would re-move many aspects of societal func-tion, resulting in a near-primal statein which the region dissolves intoan every-man-for-himself civilization.At this time, people would group to-gether with others and avoid thosewho appear to be dangerous; witha fear of infectious diseases, thosein the prodrome phase exhibiting flusymptoms would be avoided in mostcases, but those showing a full bodyrash that the media has declared asdangerous would be avoided if pos-sible. They will remain within theboundaries of the closed section ofthe world being simulated; it is as-sumed that if one person were toleave the region, another would en-ter at the same time from another,similar region, to fill the same place.All of the tendency numbers are rel-ative and none of them are guaran-tees of movement in one directionor another; the influenced movementmethod in my model is a general case

causing infected people to be avoidedand causing healthy people to clusterin groups for safety or comfort.

1.2.4 Vaccine Resistant Small-pox

In my scenario, the agent used isa sample of the India-1 vaccine-resistant strain from the Vector Labin Russia, at Novosibirsk, that waslost from the 20-ton vats that werebeing used to manufacture the biolog-ical agent. In a statement, the Rus-sian scientists announced that theyhave lost some of their stock, and sev-eral countries now, other than the USand Russia, who are legally allowedto keep a sample at the CDC and Vec-tor labs, are suspected to have strainseither of India-1 or another sample ofsmallpox, including Iran, North Ko-rea, and Iraq (Preston 95-99). If thestrain used is not the India-1 strain, itmay likely be a bioengineered virus,with the human IL-4 gene insertedinto a smallpox strain, which could becreated in as little as ”four weeks,” byusing the book ”Current Protocols inMolecular Biology,” and would cost”about a thousand dollars for eachstrain. Virus engineering is cheaperthan a used car, yet it may providea nation with a weapon as intimi-dating as a nuclear bomb” (Preston222, 225). A virus engineered withthe IL-4 gene of the host species

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provided two groups of mousepox-resistant mice with a 100 percent fa-tality rate. The pox-resistant mousenever stood a chance with only tenparticles of the engineered virus inits blood (Preston 225-226). The ac-cepted infectious dose of smallpox isbetween one and five particles, andthe average person who is infectedinhales much more than the mini-mum dose, so the test did not includeunnatural numbers of infectious par-ticles. ”The main thing that standsbetween the human species and thecreation of a supervirus is a sense ofresponsibility among individual biol-ogists? It seems possible that some-one could be playing with the genes ofsmallpox right now? No nation thatwanted to have nuclear weapons hada problem finding physicists willingto make them” (Preston 228). Biol-ogists that are willing to engineer avaccine-resistant smallpox virus arelikely in abundance as are physicistswilling to create nuclear weapons.All it would take is one person witha purpose, or recruited to a cause,to create a biological weapon thatwould resist any immunization thatthe known world could supply.

1.3 Background

Smallpox, also known as Variola ma-jor, is a fast-spreading disease with a100 percent susceptibility rate in hu-

mans who have not been immunizedin the past 10 years. The only popu-lations recently immunized are mili-tary personnel and emergency healthcontrol workers.Smallpox has a fatality rate between30 and 40 percent and spreads likewildfire both locally and globally,traveling around the world in a monthbecause of the 2 week incubation pe-riod in which no symptoms are shownfrom the infected person, as theytravel around, moving to uninfectedcities or healthy sections of a pop-ulation before the sudden outbreakcatches them by surprise, creatingmany more victims for the disease.The disease then spreads in a similarmanner to the first case in which aninfected person travels to another cityor another country. In today?s worldof long commutes and frequent va-cations and business trips, smallpoxwould travel around the world incred-ibly quickly, making quarantine al-most impossible. Thus, the scenariocreated by the terrorist organizationwould spread to many major citiesthroughout the world, creating mil-lions of cases and deaths. If the groupof infiltration terrorists were to spendtime in an airport, the result wouldbe an almost global spread within amatter of weeks (Preston 232).Also, the likelihood of the releasedstrain of smallpox being either part ofthe vaccine resistant India-1 strain, asexplained by Sderblom and Jahrling,

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or a bioengineered virus, as explainedby Preston, is quite high, whichwould negate the use of vaccine asa counter to the terrorist attack.Because of the panic caused by thenews that a weaponized, vaccine-resistant smallpox strain had been re-leased, and the chaos resulting fromthe infiltration of the city and at-tack against health facilities, any citywould quarantine itself. The panicwould shut the city?s functions down,preventing any quarantine measuresfrom being beneficial to the public.The method of attack would pre-vent the use of a military quarantinewithin the city, and the city?s self-quarantine would not be broken solong as infections run rampant andchaos reigns. (Sderblom 9)(Fenner et al. 189)

If information were released to thepublic detailing the risk of infectionat a hospital being much higher thanthat of at home, very few, if any, in-fected people would seek any medicaltreatment at all, which would thenincrease the likelihood of smallpoxspreading to others in a city throughface-to-face contact during transit ortime spent in buildings, as the ven-tilation systems of many buildings,such as townhouses, apartments, andother large-scale city housing areasare susceptible to spreading smallpoxover a large area, as was the case inthe Meschede hospital in Germany in1970, in which one victim infected 17

others, where only one of them hadseen his face or been in a room withhim (Preston 47; Fenner et al. 193).

2 Smallpox

2.1 Progression of Infec-tion

In the beginning of an infection, theperson does not realize he is infectedwith anything until 10-14 days afterexposure, when prodromal symptomsbegin, with the rash appearing twoto four days later. The first symp-toms could appear, however, as earlyas seven days after exposure, or aslate as 17 days (Akhtar 23; Fenneret al. 5; ”Medical Management ofBiological Casualties Handbook” 62;Gober and Werth; ”Smallpox,” UtahDepartment of Health; ”Smallpox In-formation Center”). This phase ispart of what makes smallpox so dev-astating; during two weeks, infectedpeople might travel to other places,and they then infect other people,making a quarantine nearly impossi-ble (”Smallpox”, World Health Or-ganization [WHO]). The above graphshows a case study of several hun-dred people, exposed to smallpox,and examined the length of timefrom initial exposure to the begin-ning of prodrome symptoms. Themean of this data is 11.5 days, and

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the standard deviation is 1.1 days.This will be modeled with the Pythongauss(mu, sigma) function. Thisfunction generates a random num-ber along a normal distribution givena mean, mu, and a standard distri-bution, sigma. Based on data fromSE172.3. Downie; Mack. 1972: andWHO/SE/73.57, Litvinjenko et al.,(Fenner et al. 188).”The prodrome or preeruptive stageof the illness starts abruptly, withfever (usually 101-104F [38.3-40C)]),malaise, headache, muscle pain, pros-tration, and often nausea and vom-iting and backache. The person usu-ally appears quite ill. The prodromeusually lasts two to four days,” witha mean of three days, and a stan-dard deviation of about eight hours.”The person is not infectious untilthe end of the prodrome, when le-sions develop in the mouth” (Akhtar,27; Atkinson et al. 283; Gober andWeese; ”Smallpox,” Utah Depart-ment of Health).However, when lesions develop, therash has not yet begun, and diagnosisof a smallpox victim in the prodro-mal stage is difficult, as symptomsclosely resemble those of flu sufferers.If someone suffering from smallpoxis towards the end of the prodrome,placing him or her into a clinic orhospital with some flu victims hasthe highest infection rates of any re-alistic situation. The next day, whenhe or she is diagnosed because of the

beginning of the rash, he or she mayhave already infected tens of flu pa-tients unknowingly. These now in-fected flu victims will recover fromthe flu, and as the smallpox prodromebegins, they will likely be treated forrelapse, perhaps in different hospitalsor clinics, and the cycle continues.After the prodrome ends, the char-acteristic centrifugal rash forms andthe disease matures.

2.2 Advancement of Rash

day 1 of rash - macules and rashspread throughout body to concen-trated areas on extremities (hands,feet, head) but covers entire body;macules begin to form papulesday 2-3 of rash - rash raises - papulesprogress slowly to form vesiclesday 3-4 of rash - fever returns in fullforceday 3-5 of rash - vesicles begin to formpustulesday 6-12 of rash - vesicles have formedpustules, which are sharply raised,typically round, tense, and firm to thetouchday 13-20 of rash - pustules drain offluid and form a crust - at this stage,infected people are no longer highlyinfectious, and the fever drops off asrecovery begins - if a victim has sur-vived so far, death is unlikelyday 21-28 of rash - crusts drop off, pa-tient has recovered

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(Medical Management of BiologicalCasualties Handbook 63; ”SmallpoxDisease Overview,” CDC)During the rash, all pustules andmarks progress at the same speed;unlike chickenpox, in which an in-fected person may see pustules thatare forming right next to a crust thatis falling off. (Atkinson et al. 283-284)This is an average progression of acase of ordinary smallpox; typicallythe victim will be fully healed be-tween day 21 and 28 of the rash, aswhen the scabs drop off, the patient isno longer contagious (”Smallpox In-formation Center”). The values willbe modeled with the mean of 24.5 andthe standard deviation of 1.167 daysof infection before the victim is curedand recovered because of the first andlast days of the end of the infectionbeing 21 days and 28 days, respec-tively, from the beginning of the rash.

2.3 Forms and FatalityRates of Smallpox

There are five recognized forms ofsmallpox, where one of the formsis a severe case of another. Thesedifferent variations of smallpox havedifferent symptoms, vastly differentfatality rates, different durations,and some slightly different infectiousrates.

1. Ordinary-type smallpox exists inabout 85 percent of cases (severityof infection is mostly random exceptthat children and the elderly are moresusceptible to a worse case, but theseverity is mostly based on the in-tensity of the rash, and the severityof the prodrome varies in severityas well.) ”In fatal cases, death oc-curred between the 10th and 16thdays of the illness” (Fenner et al.22; Hong), in the second week of ill-ness due to toxemia (”Smallpox as aBioterrorism Agent”), in ”one to twoweeks after infection as the blood-stream becomes overloaded with thevirus” (”Dermatology”, About.com).”Toxemia may be so severe as tocause death even before the rash isfully developed, but more commonlydeath, if it occurs, will be betweenthe 11th and 15th day of the rash”(”Smallpox Information Center”). Tomodel the fatality rate, the gaussfunction in python will be used witha mean of 13 and a standard devia-tion of 1 so that the third standarddeviation corresponds with the mini-mum and maximum values of 10 daysand 16 days. The fatality rate ofordinary-type smallpox is 25 percent.http://www.impactlab.com/wp-content/uploads/2009/04/a112smallpox.jpg.Confluentsmallpoxisamoresevereformofordinary, wheretherashissubstantiallysevere, pustulesandcrustingformasolidsheetoverthebody, andthepustulesdonotharden.Generally, about10percentofordinarycasesresultinconfluentsmallpox.Avictimofconfluentsmallpoxremainsinfectiousuntilcompleterecovery, andthefeverdoesnotdropoffuntilmuchlaterintheprogressionofthedisease.Infatalcases, ”deathoftenhappensatthebeginningofthecrust, justasthepatientseemstobeturningthecorner”(Preston45).Deathoccursaroundday13, wherethepustulesdrainandbegintocrust(Preston231).T omodelthefatalityrate, thegaussfunctioninpythonwillbeusedwithameanof13andastandarddeviationof1sothatthethirdstandarddeviationcorrespondswiththeminimumandmaximumvaluesof10daysand16days, asforordinarysmallpox; Confluentismerelyamoreseveretypeofordinary, andthereforehassimilartimesfordeath.Thefatalityrateforconfluentsmallpoxisaround62percent(Fenneretal.5).http ://www.mersey−gateway.org/upload/img400/A013701.jpgModifiedsmallpoxisalesssevereformofsmallpox, takingplacein2to3percentofunvaccinatedcases, modeledas2.5percent, and25percentofthosefoundintherecentlyvaccinated, yetstillinfected.Itislessinfectiousthanordinarysmallpoxandprogressesthroughthestagesofrashquicker, withahalf−lengthprodromeandadiseaselengthof14to18days, withameanof16daysandastandarddeviationof0.667days, butinotheraspects, itfollowsthesameprogression.Duringtherash, thefeverisreducedornonexistent, anditiseasilyconfusedwithchickenpoxexceptforthecharacteristicsmallpoxcentrifugalrashconcentratedonthehands, feet, andhead.Thefatalityrateformodifiedsmallpoxis0percent, andthereforeisnotfatal(Fenneretal.5).http ://medpediamedia.com/u/Modsmallpxrash.jpg/Modsmallpxrashmedium.jpgF lat, malignant, orblacksmallpoxoccursinabout7.5percentofcasesinunvaccinatedsubjects(Fenneretal.31), 74percentofwhichareinchildren.Inacaseofblackpox, asitisoftenknownas, thefeverdoesnotdropoffwiththebeginningoftherash, severetoxemicsymptomsareshown, therashbecomesincreasinglysevereonthemouthandtongue, makinginfectivityhigher, andthepustulesdonotriseorharden.Therashfeelsvelvetyandtheskinseparatesinsheets, oftenslippingoffofthevictim.Thereisnofluidintheskinlesions, andtoxemiacoupleswithrespiratoryfailuresinfatalcases.Inpatientswhosurvivethedisease, thereislittletonovisiblescarring(”BioterrorismUpdate, Smallpox”).Infatalcases, death”usuallyoccurredbetweenthe8thandthe12thday”(Fenneretal.32).T omodelthefatalityrate, thegaussfunctioninpythonwillbeusedwithameanof10andastandarddeviationof0.667sothatthethirdstandarddeviationcorrespondswiththeminimumandmaximumvaluesof8daysand12days.Thefatalityrateformalignantsmallpoxis95to100percent, whichwillberepresentedby97.5percent.http ://www.zkea.com/images/smallpox−symptoms1.jpgHemorrhagicsmallpoxoccursinabout5percentofcases, targetingadultsin90percentofcases, andisaccompaniedbyextensivebleedingintotheskin, mucousmembranes, andthegastrointestinaltract.Theprodromeistwicethelengthoftheotherformsoftheinfection, endingbetweenday5andday8, greatlyincreasingthechanceofinfectionbeforetherashdevelopsandthevictimcanbediagnosedwithsmallpox.Theprodromalsymptomsareunusuallysevereanddonotwaneuntilthescabsfalloffattheendoftheinfection.Infatalcases, deathoftenoccurssuddenlybetweenday5andday7ofillness, withrecordsofdeathfromday4today9, orduringthelastdaysoftheprodromalperiod, whenonlyafewinsignificantlesionsarepresent.Inpatientswhosurvivefor8−

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10daysthehemorrhagesappearintheearlyeruptiveperiod, andtherashisflatanddoesnotprogressbeyondthevesicularstage(Akhtar, 42; ”BioterrorismUpdate, Smallpox; ”Fenneretal.32−34, 37; ”Smallpox, ”CDC).T omodelthefatalityrate, thegaussfunctioninpythonwillbeusedwithameanof6.5andastandarddeviationof0.833sothatthethirdstandarddeviationcorrespondswiththeminimumandmaximumvaluesof4daysand9days.Thefatalityrateforhemorrhagicsmallpoxisbetween97and100percent, representedby98.5percent.http ://commons.wikimedia.org/wiki/F ile :Hemorrhagicsmallpox.jpg (Akhtar41-45; Atkinson, et al. 284-285;Center for Biosecurity, University ofPittsburgh Medical Center; Fenner etal. 4-5, 22, 32-34, 37).

2.4 Infectivity

2.4.1 Susceptibility

”The outbreak [of Variola] grows notin a straight line but in an exponen-tial rise, expanding at a faster andfaster rate. It begins as a flicker ofsomething in the straw in a barn fullof hay? but it quickly gives way tobranching chains of explosive trans-mission of a lethal virus in a virginpopulation of nonimmune hosts. Itis a biological chain reaction.” (Pre-ston 48). Unfortunately, historicaldata are available only from periodswith substantial population immu-nity either from vaccination or fromhaving survived natural infection. Inthe absence of natural disease andvaccination, the global population issignificantly more susceptible (Cen-ter for Biosecurity, UPMC).In the absence of immunity inducedby vaccination, human beings appearto be universally susceptible to infec-tion with the smallpox virus (Cen-ter for Biosecurity, UPMC). Inocula-

tion has ceased for the public sincethe Eradication campaign ended in1980. The vaccine only lasts withany potency for 3-5 years (”VaccineOverview,” CDC). Therefore, thepublic is, except for deployed mili-tary personnel and laboratory staffengaged in work with vaccinia andrelated viruses, 100 percent at riskfor infection with smallpox. In a citysuch as the model simulates, fewer ofthese people would be present thancould be simulated with any degreeof equal representation: much fewerthan 1 in 5000 people in the U.S. areeither deployed military (as deployedpersonnel would not be in the UnitedStates) or high level staff at CDC,the United States Army Medical Re-search Institute of Infectious Diseases[USAMRIID], or other similar labo-ratories, and the risk of a vaccine-resistant virus being introduced ishigh, so people with immunities areexcluded from the model.

2.4.2 Rate of Infectivity overTime of Infection

”The maximum infectivity of casesof smallpox was during the 1st weekof rash, corresponding to the periodwhen the lesions ? had ulcerated andwere releasing virus into the secre-tions of the mouth and pharynx? Atthis stage the skin lesions were intact:the large amounts of virus later shed

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from the skin were not highly infec-tious because of the physical state ofthe virus particles, enclosed withinhard dry scabs. For example, Mack(1972) found that the vast majorityof cases infected after contact withcases of smallpox that had arrivedin Europe from endemic countrieswhile incubating the disease occurredwithin 3 weeks of the initial time ofexposure?.in rural Pakistan Mack etal.. (1972b) found no evidence of sig-nificant transmission during the pro-dromal period. Theoretically, casesremained infectious until the last scabhad separated (usually from the solesof the feet) but the level of infectivityfell off greatly as the lesions? healedduring the latter part of the 2nd weekof the disease” (Fenner et al. 189).Persons carrying the virus during theincubation period cannot infect oth-ers. The frequency of infection ishighest after face-to-face contact witha patient after fever has begun andduring the first week of rash, whenthe virus is released via the respira-tory tract. Although patients remaininfectious until the last scabs fall off,the large amounts of virus shed fromthe skin are not highly infectious. Ex-posure to patients in the late stages ofthe disease is much less likely to pro-duce infection in susceptible contacts(Center for Biosecurity, UPMC).”Smallpox may be contagious duringthe prodrome phase, but is most in-fectious during the first 7 to 10 days

following rash onset” ( ”SmallpoxDisease Overview,” CDC).”The virus is readily found on theskin, in the oropharynx, and in thereticuloendothelial system through-out the rash phase (a highly infec-tious period from the appearance ofenanthema until day 10 of the rash)”(Gober and Weese).”The patient was most infectiousfrom onset of rash through the first 7to 10 days of rash. As scabs formed,infectivity waned rapidly” (SmallpoxInformation Center).The infectious period of smallpox is”From the time the rash appears -particularly in the first week of illness- until the scabs fall off” (Akhtar 20).”At the late stages, infection becomesa much less serious risk. So in short,there are roughly 8-9 days of seri-ous infection possibility with small-pox, 3-4 days in which infection is alow probability, and approximately12 days in which smallpox infectionis no threat to others” (Feasel).In summary, Most infections takeplace during the last day or two of theprodrome and the first ten days of theonset of the smallpox rash, with theexception of confluent smallpox, inwhich the infection rate does not sig-nificantly drop off after the first tendays, but only after about 20 dayswhen the scabs form and cover thesores. In all other forms of smallpox,the peak infection rates occur aroundseven days after the beginning of the

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rash, and drop quickly after day tenor 11, reaching lower values aroundday 12 or 13 and continuing to dropuntil around day 20; when the scabsform, the infectivity of a victim isvery low. persons with a severe rash[hemorrhagic or malignant or con-fluent] and involvement of the mouthand pharynx are more infectious thanthose with a slight rash (Akhtar 96).Infection for smallpox during the pro-drome begins at a very low value forthe first two days, then rising quicklyduring the second, third, and fourthdays. In the case of hemorrhagicsmallpox, with a prodrome of dou-ble the length of the other forms ofsmallpox, infectivity remained con-stant after the third day, when therash would likely have began on theinside of the throat of the victim,and remained at that constant un-til the rash began. Because of thelack of available data to accuratelygraph this data, I created my ownquartic function model for the in-fectivity of a victim over time forconfluent smallpox and nonconfluentsmallpox. My equation for noncon-fluent smallpox peaks around t=7days, drops off at a somewhat steeprate after day t=10, and is concavedown for the remainder of the daysuntil t=20, at which point the sim-ulation assumes a much lower rate,as at this time the patient is usu-ally completely scabbed over. Forhemorrhagic and malignant small-

pox, the equation was multiplied by1.1 to show the slightly increased in-fectivity of the disease in those twocases. The equation is: -5.715*10-5*t4+0.002557t3-0.0383t2+0.181t+1My equation for confluent smallpoxalso peaks around t=7 days, but doesnot drop off at the same rate after dayt=7 because of the continued high in-fection rate; instead, it maintains agradual decline and reaches a similarlow point around t=20. The equa-tion is: -2.3564*10-5*t4+0.00163t3-0.0346t2+0.181t+1.015

2.4.3 R-zero, the Rate ofInfectivity per InfectedPerson

In the past, patients suffering fromVariola major (the more severeform of the disease) became bedrid-den early (in the phase before theeruption of rash) and remained sothroughout the illness. Therefore,the spread of infection was limited toclose contacts within a small vicinity.However, the estimated R-zero value,or the number of people infected fromone case, has been estimated to bebetween three and 20, where an R-zero of five or more would spread”explosively,” which would ”get theworld to millions of smallpox casesin a few months? It has taken theworld twenty years to reach roughlyfifty million cases of AIDS. Vari-

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ola could reach that point in ten ortwenty weeks” (Preston 47-48). Someexperts have estimated today’s rateof transmission to be more on theorder of 10 new infections per in-fected person (Center for Biosecurity,UPMC). ”The other five experts dis-agreed with one another, sometimessharply, but in general they foundthat smallpox would spread widelyand rapidly. They argued forcefullywith each other (as scientists do), butin the end? ?Our general conclusionwas that smallpox is a devastating bi-ological weapon in an unimmunizedhuman population,” one of the par-ticipants said. ?If you look at thereal-world data from a 1972 outbreakin Yugoslavia, you find that the mul-tiplier of the virus was ten: the firstinfected people gave it to ten morepeople, on average. Basically, if youdon?t catch the first guy with small-pox before he kisses his wife, it goesout of control. We could be dealingwith hundreds of thousands of deaths.It will absolutely shut down interna-tional trade, and it will make 9/11look like a cakewalk. Smallpox canbring the world to its knees?” (Pre-ston 213).In summary, According to Preston?sexperts and the UPMC Center forBiosecurity, if the first person withsmallpox is not quarantined beforehe infects another, there will be nomethod of stopping it from contin-uing to spread. If the first person

or people do not want to be quaran-tined or stopped, as in a bioterroristattack, the disease will spread glob-ally, killing hundreds of thousands ofpeople. After each two weeks, thenumber of people infected increasesin a degree of magnitude: 10 to 100to 1000 in the span of a month. Therate of R-zero was 10 in an era of massvaccinations; with a population witha 100 percent susceptibility rate, R-zero will likely be higher; this will notbe shown in the model. The R-zeroof the model will remain at 10, andthe number of others infected beyondR-zero=10 will travel, as Preston ex-plains on page 232, to many places,and they will spread the infection toother cities, states, provinces, coun-tries, and continents. The simulatedinfection rate will be 9¡R-zero¡11 toaccount for differences in exact pop-ulations and situations, but it will befocused around an R-zero of 10, as thepredictions show.

2.5 Transmission

2.5.1 Inhalation

Smallpox virions behave like smokeparticles, and are almost exactly thesame size (Preston 47). To put thisinto perspective, if one were in aroom in a hospital where there wasa fire in a room in the same build-ing, anyone who could smell smoke,would likely be infected if there was

12

a smallpox patient instead of a firein the same room. The infectiousdose of smallpox is between one andfive virions, making the disease in-credibly dispersible, as it does notneed to be concentrated in order toinfect (Preston 45). ”Two hospi-tal outbreaks in the Federal Repub-lic of Germany, at Monschau (AndersPosch, 1962) and Meschede (Wehrleet al., 1970), seem certainly to havebeen airborne. In the Meschede out-break an electrician who had justflown back to the Federal Republicof Germany from Karachi, Pakistan,and who, it transpired, had neverbeen successfully vaccinated, was ad-mitted 10 days later to the isolationward of a large general hospital witha feverish illness that was suspectedto be typhoid fever. He was con-fined to his room, and 3 days afteradmission developed a rash. Small-pox was confirmed by electron mi-croscopy 2 days later and the patientwas then transferred to the smallpoxhospital. In spite of rigorous isola-tion of the patient (because of thesuspicion of typhoid fever) and, af-ter smallpox was suspected, the vac-cination of all patients and nurses inthe general hospital (in several caseswith inactivated vaccine), or inocula-tion with vaccinia-immune globulin,19 further cases of smallpox occurredthere, on all three floors of the build-ing in which the index case had beennursed. The dates of onset of these

cases are shown in Fig. 4.9A. Sev-enteen cases occurred within one in-cubation period, counting from the3 days during which the index casewas in the hospital and infectious;the last 2 were room contacts of ear-lier cases as indicated. The locationsof these patients within the hospi-tal are given in Fig. 4.9B, whichalso shows the results of tests on thecarriage of smoke through the hos-pital.” (Fenner et al. 192) In theMeschede case, a smoke machine wasused to recreate the possible spreadof smallpox particles. This is the Fig.4.9 described in the above passage.(Fenner et al. 193) Smallpox is trans-mitted mainly from person to personby infected aerosols and air dropletsspread in face-to-face contact with aninfected person after fever has begun,especially if symptoms include cough-ing, but infection can and definitelydid occur in over 15 cases from oneisolated source without any face toface contact at all, over three floorsof a building, and one case in whichthe infected person was visiting forno more than 15 minutes in a hall-way adjacent to the hallway contain-ing the closed room of the infected,which justifies an increased spread ofthe possible infection in the model.

2.5.2 Contact Transmission

The disease can also be transmit-ted by contaminated clothes and bed-

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ding, though the risk of infection fromthis source is much lower. Naturally,smallpox would be more infectiousfrom direct contact with a victim, butinhalation of smallpox virions is themost common method of transmis-sion (Center for Biosecurity, UPMC).Fenner discusses the transmission ofsmallpox through scabs on clothingor bed sheets: ”the most importantfinding was that, in Madras, virus onsuch objects was rapidly inactivated,even when they were heavily contam-inated; he concluded that fomites, orparticles of smallpox-infected biologi-cal material, were of little importancein the transmission of smallpox in In-dia. In temperate climates virus inscabs could survive on fomites such ascotton for long periods of time (Mac-Callum McDonald, 1957) ; however,virus in scabs rarely appears to havebeen a source of infection” (Fenner etal. 194). Virus transmission via in-fected clothing is a very minor risk,and contact will not be included inthe simulation other than a higherrisk of infection based on proximity.

2.5.3 Animal Transmission

There is no animal reservoir. Insectsplay no role in transmission (Centerfor Biosecurity, UPMC).Therefore, the vast majority of small-pox infections were caused by inhala-tion of particles transmitted from oralcavities through coughing of those in-

fected; thus, it stands to reason thatinfection rates would be higher uponcloser proximity or upon more timespent near an infected person. Inmy model, the rate of infection willbe a cubic function: each unit thata healthy person moves towards onewho is infected while inside the infec-tion range will increase the likelihoodof infection threefold.

2.6 Complications AfterRecovery

Between 65 and 80 percent of peo-ple who recover from smallpox willhave some form of pockmarks ontheir faces. In 0.9 percent of sur-vival cases, blindness occurs, typi-cally in those recovering from con-fluent forms of smallpox (confluent,flat, hemorrhagic). In 1.7 percent ofcases, arthritis is found (Fenner et al.47, 50). In 1-4 percent of recoveredcases, ”blindness from corneal scar-ring, growth abnormalities in chil-dren, and disfiguring or even phys-ically debilitating dermal scarring”occur (Medical Management of Bi-ological Casualties Handbook 64).”Blindness from scars on the eye iscommon” (Hong). These data setsfit well together; 0.9 percent of casesresult in blindness, which reduces thesimulated person?s vision to zero, 1.7percent of cases cause debilitating

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dermal scarring or arthritis, whichreduces the simulated person?s move-ment by 80 percent, and the remain-ing percent receive disfigurations orgrowth abnormalities in the long termwhich do not affect the short-termmodel.

3 Research, Model-

ing, and Simula-

tion

3.1 Objectives

The purpose of the project is to usea sugarscape based modeling systemin Python in order to determine theactual death toll caused by a sce-nario that relates to the one describedabove. In my model of the scenario,the modeled population is small, butthe representation of 5000 in a smalltownship or city block is represen-tative of the entire city. The repre-sentation is used because of the lim-itation in computing power; while itwould be useful to visualize the socialnetwork of the entire city, processingpower limits prevent a larger worldfrom being simulated over the sameperiod of time, and the visualizationof an entire city?s social network is inno way necessary. The same situationwould take place in every section ofthe same city and every infected city

in the world, so the result will likelybe universal; the long incubation pe-riod coupled with a few attacks inkey cities or airports would guaran-tee a similar case taking place aroundthe globe in many if not all majorcities. The model is not a physicalrepresentation of the population, butrather a visualization of the inter-actions between the 5000 people inthe model as time goes on. Differ-ent people in the model belong toseveral different social groups, as inthe world today. If one person fromone group infects another person, thenewly infected person would infectanother group of people from a sep-arate location or association; this isthe way in which a contagious diseasespreads rapidly in a large city. Thepurpose of the simulation is to showthe probable outcome of a situationwith regards to the time that the sit-uation is brought under control; thatis, when a successful quarantine hastaken place or when a new vaccinehas been developed and distributedto those not already infected. It isassumed that once the quarantine orvaccine has been implemented thatno more infections will take place inthe area. The statistics for infections,recoveries (people who have becomeimmune naturally), and deaths willthen freeze as the epidemic ends, ex-cept for the continued progression ofthe disease in those already infected.

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3.2 Related Work

Much research has been done in thefield of epidemiology with regards tosmallpox, focusing on the contain-ment of an outbreak. Several govern-ment programs have made advanceson simulating a smallpox outbreakfrom an accidental beginning, butno projects that extended periods ofresearch have uncovered have dealtwith a planned suicidal bioterrorismattack using knowing human agentsto spread the disease. No model hasbeen found that gives percentages ofany statistics by time after the begin-ning of the infection.

3.3 Rationale

This research will specify a disease -smallpox, or the Variola virus - andattempt to determine the fatality rateby percent in the large city in whichthe attack and infection first takesplace over time. It is assumed thatsimilar scenarios will take place inother cities globally, but with slightlyreduced fatality rates on average, assome other locations will likely beable to prevent the outbreak. Theproject makes the assumption thatvaccination and containment are in-effective in the scenario for the du-ration of the simulation, due to thevaccine-resistant strain or bioengi-neered strain released and the panic

of the general population; the sce-nario described in the introductionis taking place. The model has beencreated to estimate the fatality ratesbased on the response time with re-gard to ending the panic of the cityand creating a new vaccine that iseffective against the India-1 strain orthe bioengineered strain.

3.4 Procedure and Method-ology

Python will be used in the finalproject where NetLogo, an agent-based modeling program, in whicha pre-written program modeling ageneric virus infection on a popula-tion was used to obtain a basic un-derstanding of the intended result ofthe project. This is a screenshot fromthe NetLogo program; red agents areinfected, green agents are not, andgray agents are immune.The Python model will be an agent-based model with circles representingthe people in the area; each pointcan either be occupied by one agentor empty. In an agent-based model,agents, or visual representations, areused to simulate real people or things.The model is not an exactly physicalmodel, but rather a social one; in-stead of showing where an person is inthe city at a given time, it shows whoor how many other people the first

16

person is near; two agents close to-gether implies that two people wouldspend time in close proximity to oneanother, or in a situation in which oneperson would likely infect the other.If several agents are all very close, themodel may be representing a party orsocial event in which the people areall in contact with one another. Themodel also does not represent a defi-nite proximity, but rather an averageproximity of the people in that areaover the four hour period being mod-eled by one step of the program.Also, many researched works onsmallpox exist, containing many casestudies, but none that could be founddetail the average time of death afterthe first symptoms; several individ-ual points and generalizations havebeen found. In cases such as these,the Python gauss(mu, sigma) func-tion will be used as a model fromthese generalizations. The mean willbe the middle of the data range andthe third standard deviation on eitherend will be equal to the minimum andmaximum values.Testing will be done with regard tostatistics for previous outbreaks ofsmallpox and recorded death rateswith regard to variables in these out-breaks. Infection rates will also beused; infectivity has been increasedor decreased as a whole until an R-zero value of 10, with a margin oferror of no more than 1, is reached.An assumption made is that peo-

ple need to sleep and do not, there-fore, move constantly: on average, aperson would be stationary for 8-12hours during the day, shown by therepresentation being motionless fortwo to three steps every six-step day,either sleeping or in a more seden-tary activity. In the code, there isa random element included in themovement, showing that some peo-ple are less inclined to movement andmore inclined to sleeping for a longerperiod of time than others.With many sores on the feet of asmallpox sufferer, coupled with thesymptoms and illness of the diseaseitself, someone infected with small-pox would likely move much slowerthan one who is not infected (Akhtar72). This is modeled by showing thatthose infected with smallpox are only50 percent as likely to move around asa healthy person, and that those withflu symptoms but no rash, in the pro-drome of smallpox, with a malaiseaccompanied with other unpleasantsymptoms, are only 60 percent aslikely to move around, simulating de-creased towards mobility.

3.4.1 Methods, Techniques,and Construction of Pro-gram

• Create a set of data points totrack the number of agents inthe world which are healthy,

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carrying the disease, in theprodrome of smallpox, infectedwhile exhibiting a rash, recov-ered and therefore immune, anddead.

• Define the number of agents inthe world (5000).

• Define the number of terror-ist representations in the world(10).

• Create the agent class:

– Constructor of agent:(self, canvas, x, y, health)

– Self is required for a con-structor in Python

– Canvas describes the win-dow in which the agent ex-ists

– X and Y are the coordi-nates in the world

– Health describes the sta-tus of the agent at thebeginning of the world;either the agent will behealthy or the agent willhave been infected as oneof the ten terrorists in themodel

– Create variables that af-fect the agent?s move-ment:

– The agent can see ran-domly 3, 4, or 5 spaces

away determined atstartup (if the agent seesanother agent, the move-ment of that agent willbe influenced accordingly.The numbers were chosenin relation to the maxi-mum range of infection, 4spaces. Some people havegreater situational aware-ness than others and willbe able to detect a pos-sible threat before it be-comes an actual threat,while others can detecta threat as it becomes athreat, and still others areunaware until long afterthe threat has passed.

– The agent will have a ten-dency to move with arandom element account-ing for 30 percent of thetendency; outside of thisvalue there are many in-stances in which the agentwill not move; however,this value accounts for thefact that some people aremore inclined to move-ment than others.

– Agents are given values forcoordinates on the worldand Boolean values forwhether or not they areimmune; at the beginningof the program, no agent is

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immune.

– At this stage in the de-velopment, agents who areinfected will determine theduration of the stage of in-fection in which they arein at the moment.

– The disease informationarray is created, with 6pieces of information:

1. the stage of the in-fection in which theagent is currently in(carrier, prodrome,infected, healthy)

2. the type of smallpoxthat the agent is in-fected with, with anempty string (??) ifthe agent is not in-fected (ordinary, con-fluent, modified, ma-lignant, hemorrhagic)

3. the status of the in-fection with regardsto appearance: if theagent appears sick (iseither in the prodromephase or exhibiting arash), the value of theBoolean is True

4. the time (in days)since the beginning ofthe stage of infectionthe agent is currentlyin

5. the time (in days) atwhich the agent willprogress to the nextstage of the disease orrecover

6. the time (in days) atwhich the agent willdie from smallpox (ifthe agent will recover,the value is set at 100)

– The agent is given amethod which is usedfor debugging purposes,which shows the values ofall of the aforementioneddata.

• Create the method in which ifthe agent is exhibiting symp-toms of infection, whether inthe prodrome or rash phases,the infection of other agentstakes place.

– During the agent?s move,a similar method to the vi-sion method is used; ev-ery space within 4 (theinfected range) spaces isadded to a list, all emptyspaces are discarded fromthe list, and all remainingagents are processed.

– Before the agents canbe processed, however,the state of the currentagent must be evaluatedto determine the potential

19

risk factors for the otheragents. Depending on thelength of time that theagent has been infected,the potential risk can bevery high or very low.

– If the infected agent is inthe prodrome phase, therisk of infection is low;this corresponds to the lowchance of infection result-ing from a person who hasnot shown signs of the rashof smallpox. However,as the agent endures theprodrome for longer andlonger periods of time, therisk for infection rises toshow that the infected per-son develops patches onthe back of the throatin which smallpox virionscan escape the body.

– If the infected agent is ex-hibiting signs of the small-pox rash, the value differsgreatly. An agent with or-dinary or confluent small-pox has a multiplier of1.0, where an agent withhemorrhagic or malignantsmallpox has a multi-plier of 1.1, accountingfor the increased infectioncaused by greater num-bers of smallpox virionsin the bloodstream of the

infected person. Agentswith modified smallpoxhave a modifier of 0.2 toaccount for the low risk ofthe disease; it is by far themost mild of the forms ofVariola.

– After the multiplier is cal-culated, the duration ofthe rash is factored in:the equations shown in thebottom of the ”Rate of In-fectivity over Time of In-fection” section on page 10are used to determine thecomplete risk factor of theinfection taking place.

– For each agent within theinfection range, a ran-dom number is comparedto 3 to the power ofthe distance between thetwo agents * the afore-mentioned risk factor *a common multiple thatscales the random num-ber to a suitable amount;this value plays a key rolein the R-zero value, andthe common multiple wasthe key element that waschanged to obtain an R-zero of 10.

– A much lower multiple isused to determine the riskof infection for those whoare already immune and

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have recovered from thedisease once.

– If the random value ishigher than the multipliedfactor, the agent is not in-fected, and is discountedfrom the remainder of thefirst agent?s actions dur-ing that time step.

– However, if the randomvalue is lower, the agentwill become infected. Theagent takes on one of theforms of smallpox, with aprobability of taking eachform depending on thepercentage of cases of eachform obtained through re-search. The newly in-fected unit then becomesa carrier of smallpox, andthe time until the agentprogresses to the pro-drome phase is set.

• Create the method in which theagent progresses one sixth of aday with regards to the small-pox infection:

– Increase the value of dis-ease (the array of infec-tion data) which tracksthe time since the begin-ning of the stage of infec-tion by one sixth of a day

– Check if that value isgreater than the value de-

termining when or if theagent will die; if it is, setthe value in disease thatcontrols the stage of theinfection to ?dead,? whichremoves the agent fromthe simulation

– If that is not the case,check if the value is greaterthan the value determin-ing when the agent willprogress to the next phaseof the disease; if so, checkwhich part of the diseasethe agent is currently in.

– If the agent is merely car-rying the infection with-out symptoms, change thefirst value in the diseasearray to ?prodrome,? theBoolean describing visibil-ity of infection to True, thelength of time since the be-ginning of the stage of in-fection to 0, and the timeat which the agent willprogress again to a ran-dom value (rounded to thenearest sixth) as detailedin the description of theform of smallpox above. Ifthe agent is infected withhemorrhagic type small-pox, there is a large chanceof fatality during the pro-drome, and this is rep-resented with a potential

21

change in the final value ofdisease, in which the timeuntil death is recorded.

– If the agent is in the pro-dromal phase, the diseasearray becomes [?infected?,stage of disease, True, 0, arandom aspect determinedby when the agent willrecover as detailed abovein the description of theprogression of an infec-tion of smallpox, and an-other random value show-ing when or if the agentwill die (again rounded tothe nearest sixth]

– If the agent is already in-fected and has surviveduntil this point, it re-covers, setting disease to[?healthy?, ??, False, 0, 0,0], showing that the agentwill no longer progressin the disease and willnot die. The agentwill become immune, andthe corresponding Booleanwill change to show this.The potential long-termeffects of infection will becalculated, with a 0.9 per-cent chance of blindness,which reduces the vision ofthe agent to zero, and a 1.7percent chance of develop-ing severe arthritis, which

cuts the mobility or ten-dency of the agent to movein half.

• Create the method in which theagent progresses one sixth of aday with regards to the locationof the agent in the simulatedworld:

– The agent views each lo-cation which it can see (asdefined by the vision vari-able, where one step is ei-ther one location immedi-ately to the left, right, top,or bottom) and stores it inan array

– The array is pruned, weed-ing out any values thatdo not contain an agent(as only agents affect themovement of other agents)

– A coordinate of influencedmovement is created; itwill be affected by allagents that can be seen

– Iteration over every agentin the array of visibleagents considers the dis-ease of the viewed agent(a more severe form of thedisease has a greater influ-ence on the agent viewingit), the proximity of theagent (an infected agentimmediately next to the

22

agent viewing it will causea greater response thanone far away), and thepossibility that the otheragent may be friendly(agents, like people, tendto gather in groups forcomfort). At this time,people would group to-gether with others andavoid those who appearto be dangerous; with afear of infectious diseases,those in the prodromephase exhibiting flu symp-toms would be avoidedin most cases, but thoseshowing a full body rashthat the media has de-clared as dangerous wouldbe avoided if possible.

– To account for human er-ror and ignorance, the ten-dency to avoid a victimin the prodromal stagewill add 0.4 to the in-fluenced coordinate in thedirection opposite the in-fected agent, the tendencyto avoid a victim suffer-ing from smallpox with theordinary or modified rashwill add 0.6 to the influ-enced coordinate, and thetendency to avoid a vic-tim with a confluent, flat,or hemorrhagic rash, be-

cause of the appearanceof the infected, would begreater: 0.9. Those al-ready infected will notcare for the appearancesof others as much, as theywill have already resignedto their fate. Those inthe prodrome phase willavoid others who are ap-parently sick by adding 0.2to the influenced coordi-nate, while those with therash will not make any at-tempt to avoid others whoare infected at all. Theywill try to avoid thosewho are not apparently in-fected, however, for fear ofbeing shunned or rejectedor infecting others. Theywill have the same tenden-cies to avoid the healthypeople as the healthy peo-ple have of avoiding them.All of these numbers affectthe influenced coordinate,but are not guarantees ofthe movement itself.

– The movement is calcu-lated from the influencedcoordinate by adding avalue to a list for eachspace between the actualcoordinate and the influ-enced coordinate in eachdirection, adding a ran-

23

dom number between 0and 3 of cases in which theagent would not move tothe same list to representsleep or a briefly station-ary agent, and then takinga random value from thatlist as the final coordinate.

– There is a random as-pect to the movement: themovement tendency de-scribed in the creation ofthe agent is the chancethat the agent will move ifhealthy.

– After this value is calcu-lated, infected and pro-dromal agents will be lesslikely to move becauseof the malaise and othersymptoms caused by theprodrome, and the moresevere symptoms duringthe rash stage of the in-fection: agents in theprodrome will move 60percent of the time andagents exhibiting the rashwill move 50 percent ofthe time they normallywould after the calcula-tions above were made.

– If the agent is healthyor only a carrier of thedisease without showingany symptoms, it thenprogresses as the method

above describes.

• After the creation of the agentclass is completed, the basicworld is formed. It is a Sug-arscape model, displaying aclosed, square, 200X200 worldof locations.

• During each time step (repre-senting one sixth of a day), eachagent moves, possibly infectingothers and progressing throughthe disease.

• For debugging purposes, if anagent?s visual representation isclicked, the agent will displayinformation about itself, includ-ing its location, disease status,and personal status involvingmobility and vision.

• At the creation of the world, 10terrorist agents, already in thecarrier stage of the infection,are inserted into random loca-tions, followed by 4990 healthyagents.

• After each time step, the worldis redrawn. Agents that havemoved are now shown in differ-ent locations, and agents thathave progressed in the diseaseor become infected are now dif-ferent colors.

– Green agents are healthy.

24

– Yellow agents are infectedwith smallpox but havenot begun to show symp-toms.

– Orange agents are cur-rently in the prodromalphase of the infection.

– Red agents are exhibitinga fully formed smallpoxrash.

– Blue agents have recoveredand are now immune.

• Along with the world visual-ization, a running histogram isalso created. The histogramshows the number of agents ineach of the above categories aswell as the total number of liv-ing agents (white) and the totalnumber of dead agents (gray).It updates every step to showthe 800 most recent steps.

•

•

The histogram described above showsa time span of about four and a halfmonths.

3.5 Expected Results andValue to Others

This project can be expected to pro-vide an understanding of the fatalitiesand infection rates of such a popula-tion in a major city in a scenario asdescribed in the abstract, dependingon when the situation falls back un-der control and a vaccine is created.The chance of this type of scenariobeing a possibility ranges from pre-dictions of 60 percent to 80 percent,infection rates slightly after 2 monthsare around 50 percent of the popula-tion of the city, and about 75 percentof the population of the city targetedafter about 3 months are expected tobe infected.The simulation will show the expan-sion of the infection over time as wellas the expected result of the spreadof the disease at different times. Mysimulation will show the statisticsof the population during an attackbased on time after the beginningof the attack. Depending on howquickly control can be regained andhow effective the quarantine effortis; different percentages of the pop-ulation in the city (as shown by mymodel) could be saved.

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4 Conclusions

4.1 Data

The data from the trial runs are accompanied with a screenshot of the pro-gram at a point in time close to that shown in the data tables. After 10 trialruns with 10 terrorists in the scenario, the end results were as follows: Outof 5000 people in the modeled location:

1. After 1 month (180 steps = 30 days):

2. After 2 months (360 steps = 60 days):

3. After 3 months (540 steps = 90 days):

4. After 4 months (720 steps = 120 days):

5. After 5 months (900 steps = 150 days):

6. After 6 months (1080 steps = 180 days):

7. After 7 months (1260 steps = 210 days):

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27

includegraphics*chart2

4.2 Summary

The above graph shows, by per-cent, the relationships between thenumbers of healthy agents, agentscarrying smallpox, agents in the pro-drome of smallpox, agents exhibitinga rash, agents who have recovered,and agents who have died over theseven month time span of the pro-gram. It is assumed that with thegraph as a representation of the pop-ulation of the city, at the point inwhich control is regained, the quaran-tine will be effective and the vaccinewill be given universally, stoppingthe spread of the disease. Therefore,

given the data above, if control istaken and a vaccine is developed onemonth exactly after the attack be-gins, the city will have had 6 percentof its population infected, and mostlikely, around 2 percent of the pop-ulation would die by the end of theoutbreak. However, if control is nottaken and a vaccine is not developedfor four months, 94 percent of thepopulation would have been infectedand between 30 and 35 percent of thepopulation would die.

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5 References

References

[1] Akhtar, Raja S. ”Rash Illness.” 10 Apr 2003.On-line Powerpoint. Waynehealthdept.org. 20 Jan 2010.http://waynehealthdept.org/VolunteerInfo/RashIllness2.ppt.AtkinsonW, HamborskyJ,McIntyreL, WolfeS.”Smallpox”(PDF ).2005.EpidemiologyandPreventionofV accine−PreventableDiseases(TheP inkBook)(9thed.).13Nov2009.WashingtonDC :PublicHealthFoundation.pp.281 − 306.http ://www.cdc.gov/vaccines/pubs/pinkbook/downloads/smallpox.pdf.

[2][2] Bioterrorism Update: Smallpox. Emergency Medicine. 2002. 20 Jan 2010.http://www.emedmag.com/html/pre/ter/BT0102.asp.

[3] Canada.com. Smallpox. 2009. 23 Dec 2009.http://bodyandhealth.canada.com/channelsectiondetails.asp?textid =

28

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includegraphics*chart3

1482channelid = 1020relationid = 70842.CenterforBiosecurity, UniversityofP ittsburghMedicalCenter[UPMC].”SmallpoxFactSheet”.8Oct2007.6Oct2009.http ://www.upmc− biosecurity.org/website/focus/agentsdiseases/factsheets/smallpox.html.

[4][4] Center for Disease Control and Prevention [CDC]. ”Emergency Prepared-ness and Response, Disease Overview.” 30 Dec 2004. 20 Jan 2010.http://www.bt.cdc.gov/agent/smallpox/overview/disease-facts.asp.

[5] CDC. ”Emergency Preparedness and Response, SmallpoxFact Sheet, Vaccine Overview.” 30 Dec 2004. 16 Jan 2010.http://www.bt.cdc.gov/agent/smallpox/vaccination/facts.asp.

[6] CDC. ”Smallpox”, 29 Dec 2004. 16 Jan 2010.http://www.cdc.gov/vaccines/pubs/pinkbook/downloads/smallpox.pdf

[7] CDC. ”Vaccinia (smallpox) vaccine: recommendations of the Advisory Com-mittee on Immunization Practices (ACIP)”. MMWR 2001; 50(No. RR-10):1-25.

[8] CDC. ”What We Learn about Smallpox from Movies- Fact or Fiction.” 30 Dec 2004. 16 Jan 2010.http://www.bt.cdc.gov/agent/smallpox/disease/movies.asp.

[9] DeWeese, Jack. ”Simulation of the Spread of a Virus Throughout InteractingPopulations with Varying Degrees and Methods of Vaccination”. 28 Oct 2008.9 Sep 2009. http://www.tjhsst.edu/ rlatimer/techlab09/DeWeesePaperQ4-09.pdf.

[10] Feasel, Kevin. ”How Smallpox was Eliminated and whatit Means for Terrorism.” 21 Nov 2006. 18 Nov 2009.http://36chambers.wordpress.com/2006/11/21/how-smallpox-was-eliminated-and-what-it-means-for-terrorism/.

[11] Fenner F, Henderson DA, Arita I, Je?ek Z, and Ladnyi ID. ”Smallpox andIts Eradication.” Geneva: World Health Organization; 1988.

[12] Gober, Werth. ”Smallpox,” Emedicine from WebMD. 11 Dec 2009. 20 Jan2010. http://emedicine.medscape.com/article/1134582-overview.

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includegraphics*chart4

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[13] Greenley, Brendan. ”An Agent-Based Model of Recurring Epidemics ina Population with Quarantine Capabilities.” 2 Apr 2009. 9 Sep 2009.http://www.tjhsst.edu/ rlatimer/techlab09/GreenleyPaperQ4-09.pdf.

[14] Hong, John. NBC29 Health Segments, Smallpox. 21 Jan 2003. 10 Jan 2010.http://www.cecats.com/topics/smallpox.html.

[15] Jahrling PB, Huggins JW, Ibrahim MS, Lawler JV, Martin JW.”Smallpox and Related Orthopoxviruses.” In: Dembek ZF, ed. ”Med-ical Aspects of Biological Warfare.” 8 June 2009. 12 Dec 2009. Of-fice of the Surgeon General United States Army and Washington,DC: Borden Institute, Walter Reed Medical Center, 2007: 215-240.http://www.bordeninstitute.army.mil/publishedvolumes/chemBio/chembio.html.Longini, Halloran, Nizam, Y ang,Xu, Burke, Cummings, Epstein.”Containingalargebioterroristsmallpoxattack :acomputersimulationapproach.”8Aug2006.10Oct2009.http ://www.ncbi.nlm.nih.gov/pubmed/16899385.

[16][16] Manjunath, Dheeraj. ”Modeling Virus Transmissions with NetLogo usingAgent Based and System Dynamics Modeling.” 10 June 2009. 13 Nov 2009.http://www.tjhsst.edu/ rlatimer/techlab09/ManjunathPaperQ4-09.pdf.

[17] ”Medical Management of Biological Casualties Handbook.”The United States Army Medical Research Institute for In-

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fectious Diseases [USAMRIID]. 20 Sep 2006. 18 Jan 2010.http://www.usamriid.army.mil/education/bluebookpdf/USAMRIID

[18] Preston. The Demon in the Freezer. New York, N.Y. : Random House, 2002.

[19] ”Simulation Examines Effects Of Smallpox Attack.” GovPro. 14 Jan 2003.18 Oct 2009. http://govpro.com/issue 20030101/gov imp 28875/.

[20] ”Smallpox as a Bioterrorism Agent.” Minnesota Department of Health. 31Dec 2002. 20 Jan 2010. http://www.docstoc.com/docs/445678/Smallpox.

[21] ”Smallpox, Dermatology.” About.com. 30 Nov 2003. 20 Jan 2010.http://dermatology.about.com/cs/smallpox/a/smallpox.htm.

[22] ”Smallpox Information Center.” Phages.org. 2007. 20 Jan 2010.http://smallpox.phages.org/.

[23] ”Smallpox (Variola).” Utah Department of Health, Bureau of Epidemiology.Dec 2002. 16 Jan 2010. http://health.utah.gov/epi/factsheets/smallpox.html.”Smallpox.”WorldHealthOrganization[WHO].23Dec2009.http ://www.who.int/mediacentre/factsheets/smallpox/en/.

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