session 1 - bt epi response training - outbreak investigation

7/28/2019 Session 1 - BT Epi Response Training - Outbreak Investigation

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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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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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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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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

session 1 - bt epi response training - outbreak investigation

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