Biological Attack Model (BAM) Progress Report March 8

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Biological Attack Model(BAM)Progress
ReportMarch 8

• Sponsor Dr. Yifan Liu
• Richard Bornhorst
• Robert Grillo
• Deepak Janardhanan
• Shubh Krishna
• Kathryn Poole

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Agenda

• Project Plan
• Work Breakdown
• Biological Agent Parameters
• Assumptions Revisited
• Preliminary Model Overview
• Current Modeling Issues

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Project Plan
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Work Breakdown

• 320 of 875 man-hours completed.
• Ahead of schedule on modeling
• End modeling phase by next brief to give an extra
  week to testing, evaluation, analysis, and
  recommendations (4 weeks)
• Develop early skeleton for final report

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Biological Agent Parameters

• Smallpox (ß 3) (d 30)
• Incubation Period 7-17 days
• Prodrome Period 2-4 days
• Symptomatic Period 20 days
• Ebola (ß 1-2) (d 40-90)
• Incubation Period 2-20 days
• Prodrome Period 2-4 days
• Symptomatic Period 6-9 days
• Viral Encephalitis (ß 3-4) (d 3-60)
• Incubation Period 5-15 days
• Prodrome Period 2-4 days
• Symptomatic Period 7-14 days

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Assumptions Revisited

• Attack Assumptions
• Single source where a certain number of people
  are initially exposed
• Diseases will be transmitted person to person
  rather than airborne or food borne
• Detected 24 hours after incident (may adjust for
  future analysis)
• Population Assumptions
• Constant population with no immigration/emigration
  , births, or deaths that arent related to the
  disease
• People in the incubation stage (non-contagious)
  are considered susceptible in terms of quarantine
  and treatment since they are not yet known to be
  infected

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Assumptions Revisited

• Quarantine Assumptions
• Various percentages of the population are
  quarantined to analyze effectiveness
• Isolation of confirmed and suspected cases with
  vaccination and quarantine of contacts traced to
  these cases
• All other quarantine is voluntary confinement
• A percentage of the population cannot be
  quarantined
• Vaccination and Treatment Assumptions
• A percentage of population is already vaccinated
  (when applicable)
• Emergency response and medical staff already
  vaccinated (if available)
• Treatments are available for recovering those
  that receive it
• Vaccination and treatment have no significant
  side effects
• Those in quarantine without symptoms receive
  available vaccination
• Those showing symptoms do not receive vaccination
  (treatment only)

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Two Phases

• First Phase
• The spread of the pathogen before detection
• Initial assumption is detection occurs after 24
  hours, but this will be adjusted to analyze the
  importance of early detection
• Only three states during this phase Susceptible,
  Infected, Infectious
• Second Phase
• Occurs after outbreak has been identified
• The status of states at end of first phase
  provide initial conditions for second phase
• Containment strategies employed

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Preliminary Model Diagram
Track 10 different populations
SQi1Qi2QsI1I2RNRTRDD N
Recovered With Treatment RT
Quarantined Infected Qi1
Susceptible S
Infected I1
Quarantined Infectious Qi2
Dead D
Quarantined Susceptible QS
Infectious I2
Disabled RD
Recovered Without Treatment RN
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Preliminary Model Parameters

• Transmission Rate (b)
• Average Incubation Length (m1)
• Average Infectious Length (m2)
• Disease Mortality Rate (d)
• Quarantine Rate (q)
• Tracing Close Contacts of Infectious (a)
• Number of Treated Per Day (f)
• Treatment Efficacy Period (b)
• Disability Ratio (g)
• Total Population (N)

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Preliminary Model Parameters (Excel snapshot)
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Example Plot10,000 treated per day, 30
Quarantine Rate
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Example Plot10,000 treated per day, No
Quarantine
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Example Plot20,000 treated per day, 30
Quarantine Rate
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Current Modeling Issues

• Modeling a Coherent Detection Scheme
• Disease incubation periods vs. appearance of
  symptoms
• Arriving at a Balance between Number of States
  Reality
• Risk of Inaccuracy vs. simplification
• Recovery without treatment, Side effects.
• Integrity checks to be built in
• Containment as a combination of Reducing Contacts
  and Treatment Resource Allocation
• Effective Treatment allocation issue
• Availability of Emergency Responders
• Effect of varying ß due to Intervention efforts
• Diverse Containment strategies emerging for
  different diseases
• More data available on Smallpox than the others
• Translating results into Information for a
  Decision Maker
• Use of percentages of population vs. absolute
  numbers

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Questions
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