session 1 - bt epi response training - outbreak investigation
TRANSCRIPT
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BTEPIDEMIOLOGIC RESPONSE
TEAM TRAINING
SESSION 1
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Objectives of training
1. To understand clinical description andepidemiology
2. To understand the disease case definition, lab
specimens needed, labs role, and lab tests needed
for confirmation
3. To understand prevention and control procedures
including available treatment and post-exposure
prophylaxis, isolation and infection controlprocedures.
4. To understand contact tracing and surveillance
procedures
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Team Roles and Responsibilities
1. Outbreak management staff
2. Case Ascertainment staff/active surveillance
3. Face-to-face interviewers
4. Telephone interviewers
5. Data base support
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Employee Health
1. Education of risks of disease from exposureto BT agents or infectious patients
2. Vaccination
3. Personal protective equipment (PPE)
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BT AGENTS
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Prioritization Categories
Category A
High public health impact and publicperception
Variable dissemination potential
Comprehensive PH preparedness
Category B
Less public health impact
Variable dissemination potential Less comprehensive PH preparedness
Category C
Addressed with current preparedness efforts
(BT/EID)
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Category A Agents
Variola virus - smallpox
Bacillus anthracis - anthrax
Yersinia pestis - plague
Francisella tularensis - tularemia
C. botulinum toxins - botulism
Filo and Arenaviruses - VHFs
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Characteristics of Category A Agents
Infectious via aerosol
Organisms fairly stable in aerosol
Susceptible civilian populations
High morbidity and mortality
Person-to-person transmission
Difficult to diagnose and/or treat
Previous development for BW* Priority agents may exhibit all or some of the above characteristics
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Characteristics of Category B Agents
Coxiella burnetiiQ fever
Brucella spp. - brucellosis
Burkholderia mallei - glandersAlphaviruses (VEE, WEE, EEE) - encephalitis
Ricinus communis - Ricin
Epsilon toxin from clostridium perfingensStaphylococcus enterotoxin B
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Category C Agents
Emerging infectious disease agents(Hantavirus, Nipah virus, etc.)
SalmonellaE-coli O157:H7
Vibrio choleraecholeraCryptosporidium parvum -
cryptosporidiosis
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OUTBREAK
INVESTIGATION
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Definition
Occurrence of more cases of disease than
expected
Nosocomial outbreak-any group ofillnesses of common etiology occurring in
patients of a medical care facility
acquired by exposure of those patients tothe disease agent while confined in such a
facility.
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Reasons to investigate
Control/prevention
Research opportunities
Training
Public, political, or legal concerns
Program considerations
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Control / Prevention
Where are we in the outbreak?
Goals will be different depending on answer(s)
Cases continuing to occur
Goal: prevent further cases Assess population at risk, implement control
measures
Outbreak appears to be coming to an end
Goal: prevent future outbreaks
Identify factors contributing to outbreak,implement measures to prevent similar events in
the future
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Steps of an OutbreakInvestigation
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1. Preparation
Investigation
Scientific knowledge
Review literature Consult experts
Sample questionnaires
Supplies
Consult with laboratory
Equipment
Laptop, camera etc.
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Preparation, cont.
Administration-assure personnel resources, funding
Travel arrangements (orders)
Approval Personal matters
Consultation-make sure you know your role and its
parameters
Lead investigator or just lending a hand?
Know who to contact when you arrive
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2. Establish existence of an outbreak
Is an outbreak truly occurring?
True outbreak
Sporadic and unrelated cases of samedisease
Unrelated cases of similar unrelated
disease Determine the expected number of cases before
deciding whether the observed number exceedsthe expected number
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Establish outbreak existence, cont.
Comparing observed with expected
through surveillance records for
notifiable diseaseshospital discharge data, registries,
mortality statistics
data from other facilities, states,surveys of health care providers
community survey
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3. Verify the Diagnosis
Ensure proper diagnosis and rule out lab error
as the bias for increased diagnosis
Review clinical findings, lab results Summarize clinical findings with frequency
distributions
Characterize spectrum of diseaseVerify diagnosis
Develop case definition
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Verify the Diagnosis cont.
See and talk with patients if at all possible
Better understand clinical features
Mental image of disease and the patients
affectedGather critical information
Source of exposure
What they think caused illnessKnowledge of others with similar illness
Common denominators
Helpful in generating ideas for hypothesis about
etiology and spread
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4a. Establish a case definition
Case definition
Standard set of criteria for deciding whetheran individual should be classified as havingthe health condition of interest
Includes clinical criteria and restrictions bytime, place and person
Must be applied consistently and withoutbias to all persons under investigation
Must not containan exposure of risk factoryou want to test
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4a. Establish a case definition, cont.
Classification
Definite (confirmed)
Laboratory confirmedProbable
Typical clinical features without lab
confirmationPossible (suspected)
Fewer of the typical clinical features
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4a. Establish a case definition, cont.
Early in investigation may use a loose case definition
Better to collect more than necessary so you
dont need to make repeat visits Identify extent of problem and population
affected
Generating hypotheses
Later when hypotheses are sharpened investigator may
tighten case definition
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4b. Identify and count cases
Target health care facilities where diagnosislikely to be made
Enhanced passive surveillance e.g. letterdescribing situation and asking for reports
Active surveillance e.g. phone or visit facilityto collect information
Alerting the public Media alert to avoid contaminated food
product and seek medical attention ifsymptoms arise
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4b. Identify and count cases, cont.
OB population restricted and large
proportion of cases are unlikely to be
diagnosed e.g. on a cruise ship
Survey entire population
Always ask case-patients if they know of
any others ill with the same symptoms
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4b. Identify and count cases, cont.
Information to be collected about every case
Identifying information
Re-contact if additional questions come up Notification of lab results and outcomes of
investigation
Check for duplicate records
Map geographic extent
Demographics
Provide person characteristics for defining
population at risk
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4b. Identify and count cases, cont.
Information to be collected about every case cont.
Clinical findings
Verify case definition met Chart time course
Supplemental date e.g. deaths
Risk factor information
Tailored to specific disease in question
Reporter information
Id of person making report
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4b. Identify and count cases, cont.
Collection forms
Standard case report form
QuestionnaireData abstraction form
Line listing
Abstraction of selected critical itemsfrom above forms
Contains key information
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5. Perform Descriptive
Epidemiology
After collection of data characterize
the outbreak by:
Time
Place
Person
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Time
Epidemic curve
Histogram of the number of cases by their date ofonset
Visual display of the outbreaks magnitude andtime trend
Where you are in the time course of the outbreak
Future course?
Probable time period of exposure
Helps in development of questionnaire focusingon that time period
Common source vs. Propagated
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Place
Geographic extent of problem
Clusters or patterns providing importantetiologic clues
Spot maps Where cases live, work or may have been
exposed
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Person
Determine what population at risk
Usually define population by hostcharacteristics or exposure
Use rates to identify high-risk groups Numerator = number of case
Denominator = number of people at risk
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Develop Hypotheses
Hypotheses should address
Source of the agent
Mode of transmission
Vector or vehicle
Exposure that caused disease
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Develop Hypotheses
Generating the hypothesis
What do you know about the disease?
Reservoir, transmission, common vehiclesand known risk factors
Talk to several case-patients
Use open ended questions
Ask lots of questions Talk to local health department staff
Use descriptive epidemiology e.g. epi curve
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7. Test Hypotheses
Evaluate the credibility of yourhypotheses
Compare with established facts When clinical, lab, environmental and/or
epi data undoubtedly support hypothesis
Use analytic epidemiology to quantify
relationships and explore the role of chance Cohort studies
Case control studies
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7. Test Hypotheses, cont.
Cohort
Small, well defined population
Contact each attendee and ask a series of
questions Ill Vs not ill
Look for source exposure
Attack rate is high among those exposed
Attack rate is low among those not exposed Most of the cases were exposed, so that the exposure
could explain most, if not all, of the cases
Relative risk = measure of association between
exposure and disease
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7. Test Hypotheses, cont.Case-control
Population not well defined
Case patients and comparison group(controls) questioned about exposure(s)
Compute measure of association =
Odds Ratio Quantify relationship between exposure
and disease
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8. Refine hypotheses and do
additional studies
Epidemiologic
When analytical epi unrevealing need toreconsider your hypotheses
Go back and gather more information
Conduct different studies
Laboratory
Additional tests
Environmental studies
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9. Implement Control /Prevention
Measures
Implement control measures as soon aspossible
May be aimed at agent, source, orreservoir
Short or long term
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10. Communicate the Findings
Orally within facility/community
Local health authorities and persons responsible
for implementation of control and preventionmeasures
Written reports (consider publication) forplanning, record of performance, legal issues,
reference, adding to knowledge base