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Outbreak Investigation: The First 48. Rachel Radcliffe, DVM, MPH Career Epidemiology Field Officer Division of Infectious Disease Epidemiology West Virginia Dept. of Health and Human Resources. Objectives. Explain the definition of an outbreak

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Outbreak Investigation: The First 48

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Outbreak investigation the first 48

Outbreak Investigation:The First 48

Rachel Radcliffe, DVM, MPH

Career Epidemiology Field Officer

Division of Infectious Disease Epidemiology

West Virginia Dept. of Health and Human Resources


Objectives

Objectives

  • Explain the definition of an outbreak

  • Describe initial actions of outbreak investigation


What is an outbreak

What is an Outbreak?

  • Occurrence of more cases than expected

  • Localized increase in the incidence of disease


How are outbreaks detected

How are outbreaks detected?

  • Review and analyze surveillance data

  • Clinicians alert health departments to unusual events or clusters

  • Receive reports by patients or other community members


To investigate or not investigate

To Investigate or Not Investigate?

  • Variety of Factors to Consider

    • Disease

    • Health department resources

    • External factors


Steps of outbreak investigation

Steps of Outbreak Investigation

  • Prepare for field work

  • Establish existence of outbreak

  • Verify diagnosis

  • Implement control and prevention measures

  • Construct a working case definition

  • Find cases systematically and record information

  • Descriptive epidemiology

  • Evaluate hypotheses epidemiologically

  • Reconsider, refine, and re-evaluate hypotheses

  • Evaluate lab/environmental findings

  • Initiate or maintain surveillance

  • Communicate findings


Steps of outbreak investigation1

Steps of Outbreak Investigation

  • Prepare for field work

  • Establish existence of outbreak

  • Verify diagnosis

  • Implement control and prevention measures

  • Construct a working case definition

  • Find cases systematically and record information

  • Descriptive epidemiology

  • Evaluate hypotheses epidemiologically

  • Reconsider, refine, and re-evaluate hypotheses

  • Evaluate lab/environmental findings

  • Initiate or maintain surveillance

  • Communicate findings


Prepare for field work

Prepare for Field Work

  • Scientific and investigative issues

    • Review literature

    • Consult subject matter experts

    • Consult laboratory

    • Supplies and equipment

  • Management and operational issues

    • Designate team leader

    • Communications plan

    • Travel, lodging, and transportation


Establish existence of an outbreak

Establish Existence of an Outbreak

  • Try to determine baseline occurrence of disease

  • Compare observed number of cases to expected number of cases for disease

  • Consider other possible causes for increase


Verify the diagnosis

Verify the Diagnosis

  • Similar to verifying existence of outbreak

  • Review clinical findings and lab results

    • Consult with clinical experts

  • Visit / Interview patients with disease

  • Summarize clinical findings with frequency distributions


Line lists

Line Lists

  • List of cases with demographic, clinical, and possibly laboratory information

  • Examine number of affected to determine if over baseline

    • Establish existence of outbreak

  • Examine clinical findings and lab results

    • Verify diagnosis


Implement control measures

Implement Control Measures

  • Determined by clinical picture

  • May change as outbreak continues

  • Example:

    • Implement droplet precautions when outbreak of respiratory illness reported


Construct a working case definition

Construct a Working Case Definition

  • Standard set of criteria for deciding whether an individual should be classified as having disease of interest

  • Not 100% accurate

  • Use broad case definition early in investigation

  • Revise as investigation continues


Parts of a case definition

Parts of a Case Definition

  • Clinical criteria

  • Laboratory criteria

  • Restrictions by person, place, and time

  • Do not include exposure or risk factor criteria


Different categories of case definitions

Different Categories of Case Definitions

  • Confirmed

    • Clinical criteria plus lab confirmation

  • Probable

    • Clinical criteria without lab confirmation

  • Suspect

    • Sometimes used

    • Fewer clinical criteria

  • Categories helpful when diagnosis uncertain


Example case definition

Example Case Definition

  • Three or more loose stools or episodes of diarrhea in a 24 hour period in a student or staff member of School A with illness onset after September 21, 2010


Example case definition clinical criteria

Example Case Definition Clinical Criteria

  • Three or more loose stoolsor episodes of diarrhea in a 24 hour period in a student or staff member of School A with illness onset after September 21, 2010


Example case definition person restriction

Example Case Definition Person Restriction

  • Three or more loose stools or episodes of diarrheain a 24 hour period in a student or staff member of School A with illness onset after September 21, 2010


Example case definition place restriction

Example Case Definition Place Restriction

  • Three or more loose stools or episodes of diarrhea in a 24 hour period in a student or staff member of School A with illness onset after September 21, 2010


Example case definition time restriction

Example Case Definition Time Restriction

  • Three or more loose stools or episodes of diarrhea in a 24 hour period in a student or staff member of School A with illness onset after September 21, 2010


Suspected influenza outbreak report

Suspected Influenza Outbreak Report

  • Daycare reports multiple students with influenza

  • Parents calling daycare panicked

  • What are your next steps?


Suspected influenza outbreak initial investigation steps

Suspected Influenza Outbreak Initial Investigation Steps

  • Determine existence of an outbreak

  • Verify diagnosis

    • Line list

    • Use standard ILI case definition

      • Fever >100 degrees F plus cough or sore throat

    • Discuss potential laboratory testing

      • Nasopharyngeal swabs


Suspected influenza outbreak line list

Suspected Influenza Outbreak Line List

* There are 50 kids in the daycare center


Suspected influenza outbreak frequency distributions

Suspected Influenza Outbreak Frequency Distributions

  • 1 out of 5 (20%) have fever > 100 degrees F

  • 2 out of 5 (40%) have cough

  • 1 out of 5 (20%) have sore throat

  • 1 out of 5 (20%) has not symptoms

  • None meet ILI case definition


Suspected influenza outbreak frequency distributions1

Suspected Influenza Outbreak Frequency Distributions

  • 1 out of 5 (20%) have fever > 100 degrees F

  • 2 out of 5 (40%) have cough

  • 1 out of 5 (20%) have sore throat

  • 1 out of 5 (20%) has not symptoms

  • None meet ILI case definition

  • Not likely to be influenza outbreak


Shingles outbreak report

Shingles Outbreak Report

  • Reported from nursing home

  • Four residents with shingles-like rash

  • Shingles not infectious


Shingles outbreak report1

Shingles Outbreak Report

  • Reported from nursing home

  • Four residents with shingles-like rash

  • Shingles not infectious

  • Recommended to consult with dermatologist to verify shingles diagnosis

    • 1 diagnosed with shingles

    • 2 diagnosed with eczema

    • 1 diagnosed with contact dermatitis


Shingles outbreak report2

Shingles Outbreak Report

  • Reported from nursing home

  • Four residents with shingles-like rash

  • Shingles not infectious

  • Recommended to consult with dermatologist to verify shingles diagnosis

    • 1 diagnosed with shingles

    • 2 diagnosed with eczema

    • 1 diagnosed with contact dermatitis

  • Outbreak ruled out!


Steps of an outbreak investigation

Steps of an Outbreak Investigation

  • Prepare for field work

  • Establish existence of outbreak

  • Verify diagnosis

  • Implement control and prevention measures

  • Construct a working case definition

  • Find cases systematically and record information

  • Descriptive epidemiology

  • Evaluate hypotheses epidemiologically

  • Reconsider, refine, and re-evaluate hypotheses

  • Evaluate lab/environmental findings

  • Initiate or maintain surveillance

  • Communicate findings


Steps of an outbreak investigation1

Steps of an Outbreak Investigation

  • Prepare for field work

  • Establish existence of outbreak

  • Verify diagnosis

  • Implement control and prevention measures

  • Construct a working case definition

  • Find cases systematically and record information

  • Descriptive epidemiology

  • Evaluate hypotheses epidemiologically

  • Reconsider, refine, and re-evaluate hypotheses

  • Evaluate lab/environmental findings

  • Initiate or maintain surveillance

  • Communicate findings


Thank you

Thank You

Questions?


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