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Author: Bela T. Matyas
Epidemiology Program: Outbreak Investigation Epidemiology Program: Outbreak Investigation
Epidemiology Epidemiology
Epidemiology, cont. Epidemiology, cont.
Epidemiology: Interpretation of Results Epidemiology: Interpretation of Results
Attributes of a Public Health Surveillance System Attributes of a Public Health Surveillance System
Confidentiality Confidentiality
Basic Structure of Public Health Surveillance Basic Structure of Public Health Surveillance
Factors Affecting Occurrence of Infection Factors Affecting Occurrence of Infection
How Communicable Diseases are Transmitted How Communicable Diseases are Transmitted
General Principles of the Epi Field Investigation General Principles of the Epi Field Investigation
Steps in Conducting a Field Investigation Steps in Conducting a Field Investigation
Confirm the Diagnosis Confirm the Diagnosis
Confirm the Existence of an Outbreak Confirm the Existence of an Outbreak
Determine the Number of Cases Determine the Number of Cases
Develop an Initial Case Definition Develop an Initial Case Definition
Case Definitions Case Definitions
“Describe” the Outbreak “Describe” the Outbreak
Descriptive Epidemiology Descriptive Epidemiology
Person: Frequency Tables<br> Person: Frequency Tables
Place: Spot Maps Place: Spot Maps
Place: Common Exposure Location Place: Common Exposure Location
Place: Common Exposure Location (cont.) Place: Common Exposure Location (cont.)
Point-Source Exposure Point-Source Exposure
Ongoing Exposure Ongoing Exposure
Secondary Exposures Secondary Exposures
Identify Persons At Risk Identify Persons At Risk
Develop a Hypothesis Develop a Hypothesis
Hypothesis Hypothesis
Case Definition vs. Hypothesis Case Definition vs. Hypothesis
Compare Hypothesis to Facts Compare Hypothesis to Facts
Conduct an Analytical Study Conduct an Analytical Study
Analytical Epidemiology Analytical Epidemiology
Measures of Association Between Exposure & Disease Measures of Association Between Exposure & Disease
Cohort Studies Cohort Studies
Attack Rate: Measure of Occurrence Attack Rate: Measure of Occurrence
Estimating Risks Associated with “Exposure” Estimating Risks Associated with “Exposure”
Using the 2 by 2 Table to Calculate Relative Risk Using the 2 by 2 Table to Calculate Relative Risk
Case-Control Studies Case-Control Studies
Odds Ratio from Case-Control Studies Odds Ratio from Case-Control Studies
Using the 2 by 2 Table to Calculate Odds Ratio Using the 2 by 2 Table to Calculate Odds Ratio
Validity of Findings Validity of Findings
Examples of Bias Examples of Bias
Confounding Confounding
Evaluating the Role of Chance Evaluating the Role of Chance
Evaluating the Role of Chance, cont. Evaluating the Role of Chance, cont.
P Values and Confidence Intervals, Example 1 P Values and Confidence Intervals, Example 1
P Values and Confidence Intervals, Example 2 P Values and Confidence Intervals, Example 2
P Value: Effect of Sample Size P Value: Effect of Sample Size
P Value: Effect of Sample Size, cont. P Value: Effect of Sample Size, cont.
P Value: Effect of Sample Size, cont. P Value: Effect of Sample Size, cont.
The Significance of “Significance” The Significance of “Significance”
Implement Control & Prevention Measures Implement Control & Prevention Measures
Outbreak Investigation and Control Outbreak Investigation and Control
Foodborne Diseases Foodborne Diseases
Foodborne Disease: Factors Affecting Epidemiology & Surveillance Foodborne Disease: Factors Affecting Epidemiology & Surveillance
Foodborne Diseases:  Scope Foodborne Diseases: Scope
Transmission of Foodborne Diseases Transmission of Foodborne Diseases
Foodborne Disease Agents Foodborne Disease Agents
Non-Foodborne Routes of Disease Transmission Non-Foodborne Routes of Disease Transmission
A Foodborne Outbreak of Shigellosis A Foodborne Outbreak of Shigellosis
Notification Notification
Case Ascertainment Case Ascertainment
Interviews Interviews
Case Definition Case Definition
Outbreak Cases: Patrons Outbreak Cases: Patrons
Outbreak Cases: Staff Outbreak Cases: Staff
Estimated Attack Rate Estimated Attack Rate
Epidemic Curve Epidemic Curve
Foodborne Disease Outbreak Foodborne Disease Outbreak
Exposure Assessment Exposure Assessment
Exposure Assessment, cont. Exposure Assessment, cont.
Exposure Assessment, cont. Exposure Assessment, cont.
Lab Results: Pulsed-Field Gel Electrophoresis Lab Results: Pulsed-Field Gel Electrophoresis
Environmental Findings Environmental Findings
Conclusions Conclusions
Policy Implications Policy Implications
Outbreak of Giardiasis: Milton, MA, 2003 Outbreak of Giardiasis: Milton, MA, 2003
Giardiasis:  Epidemiology<br> Giardiasis: Epidemiology
Giardiasis: Epidemiology, cont. Giardiasis: Epidemiology, cont.
Giardiasis:  Clinical Giardiasis: Clinical
Background:  Outbreak Background: Outbreak
Background:  Country Club Background: Country Club
Water Supply for Milton Water Supply for Milton
Objectives of Investigation Objectives of Investigation
Method:  Retrospective Cohort Study Method: Retrospective Cohort Study
Questionnaire Questionnaire
Case Definitions Case Definitions
Results of Questionnaire Results of Questionnaire
Breakdown of Cases (n = 149) Breakdown of Cases (n = 149)
Symptoms of Cases (N = 149) Symptoms of Cases (N = 149)
Symptoms of Cases (N = 149) Symptoms of Cases (N = 149)
Duration of Symptoms for Cases (n = 80) Duration of Symptoms for Cases (n = 80)
Age and Sex Age and Sex
Percent Cases by Age Group Percent Cases by Age Group
Epidemic Curve (n = 135) Epidemic Curve (n = 135)
Newspaper Heading Newspaper Heading
Epidemiology Program: Outbreak Investigation: Slide 97 Epidemiology Program: Outbreak Investigation: Slide 97
Further Case Definitions Further Case Definitions
Rationale for 60-Day Time Frame<br> for Secondary Cases before October 5 Rationale for 60-Day Time Frame
for Secondary Cases before October 5
Cases by Status Cases by Status
Epidemic Curve (n = 135) Epidemic Curve (n = 135)
Possible Fecal Shedding Possible Fecal Shedding
Risk Factors for Illness Among <br>Primary Cases (N = 30) Risk Factors for Illness Among
Primary Cases (N = 30)
Primary Cases (exposure to pools) Primary Cases (exposure to pools)
Stratified Analysis: Kiddy Pool Exposure and Giardiasis by Age Group Stratified Analysis: Kiddy Pool Exposure and Giardiasis by Age Group
Stratified Analysis: Age Group and<br>Giardiasis by Kiddy Pool Exposure Stratified Analysis: Age Group and
Giardiasis by Kiddy Pool Exposure
Dose Response Dose Response
Household-Level Risk Factors Household-Level Risk Factors
Recommendations Recommendations
Follow-Up Follow-Up
Confirmed Cases of Giardia, Milton, 1999-2004 Confirmed Cases of Giardia, Milton, 1999-2004
Conclusions Conclusions
A Foodborne Outbreak of Hepatitis A A Foodborne Outbreak of Hepatitis A
Notification Notification
Initial Investigation Initial Investigation
Initial Investigation Initial Investigation
Initial Investigation Initial Investigation
Initial Investigation Initial Investigation
Initial Investigation, cont. Initial Investigation, cont.
Initial Investigation, cont. Initial Investigation, cont.
Initial Investigation, cont. Initial Investigation, cont.
Initial Investigation, cont. Initial Investigation, cont.
Initial Investigation, cont. Initial Investigation, cont.
Hepatitis A Cases Associated with Marshfield Outbreak February-March 2004 Hepatitis A Cases Associated with Marshfield Outbreak February-March 2004
Initial Investigation, cont. Initial Investigation, cont.
Initial Investigation, cont. Initial Investigation, cont.
Initial Investigation, cont. Initial Investigation, cont.
Initial Investigation, cont. Initial Investigation, cont.
Initial Investigation, cont. Initial Investigation, cont.
Initial Investigation, cont. Initial Investigation, cont.
Initial Investigation, cont. Initial Investigation, cont.
Analytical  Investigation Analytical Investigation
Analytical Investigation, cont. Analytical Investigation, cont.
Analytical Investigation, cont. Analytical Investigation, cont.
Analytical Investigation, cont. Analytical Investigation, cont.
Analytical Investigation, cont. Analytical Investigation, cont.
Restaurant 4 Odds Ratio Restaurant 4 Odds Ratio
Restaurant 4 Odds Ratio Restaurant 4 Odds Ratio
Restaurant 4 Odds Ratio Restaurant 4 Odds Ratio
Restaurant 4 Odds Ratio Restaurant 4 Odds Ratio
Restaurant 4 Odds Ratio Restaurant 4 Odds Ratio
Restaurant 4 Odds Ratio Restaurant 4 Odds Ratio
Further Investigation Further Investigation
Further Investigation Further Investigation
Further Investigation Further Investigation
Further Investigation, cont. Further Investigation, cont.
Further Investigation, cont. Further Investigation, cont.
Further Investigation, cont. Further Investigation, cont.
Control & Prevention Control & Prevention
Tularemia: Martha’s Vineyard, Massachusetts Summer 2000 Tularemia: Martha’s Vineyard, Massachusetts Summer 2000
Tularemia Tularemia
Clinical Presentation Clinical Presentation
Tularemia on Martha’s Vineyard Tularemia on Martha’s Vineyard
Recognition of the Outbreak, July 2000 Recognition of the Outbreak, July 2000
Methods Methods
Case Definition Case Definition
Case-Control Study – Methods Case-Control Study – Methods
Environmental Investigation Environmental Investigation
Results Results
Pneumonic Tularemia, By Week of<br>Illness Onset – Martha’s Vineyard, 2000 Pneumonic Tularemia, By Week of
Illness Onset – Martha’s Vineyard, 2000
Characteristics of Cases and Controls, <br>MV, 2000 Characteristics of Cases and Controls,
MV, 2000
Characteristics of Cases and Controls, MV, 2000, cont. Characteristics of Cases and Controls, MV, 2000, cont.
Time Spent Outdoors - Martha’s Vineyard, 2000 Time Spent Outdoors - Martha’s Vineyard, 2000
Logistic Regression Logistic Regression
Environmental Results Environmental Results
Environmental Results Environmental Results
Conclusions Conclusions
Limitations Limitations
Recommendations Recommendations
Challenges in Recognizing a Bioterrorist Attack Challenges in Recognizing a Bioterrorist Attack
Some Indicators of Bioterrorism Events Some Indicators of Bioterrorism Events
Public Health Bioterrorism Surveillance Plan Public Health Bioterrorism Surveillance Plan
Early Detection of a BT Event: Finding a Zebra Among Horses Early Detection of a BT Event: Finding a Zebra Among Horses
Salmonellosis in Oregon, 1984 Salmonellosis in Oregon, 1984
Salmonellosis in Oregon, cont. Salmonellosis in Oregon, cont.
Salmonellosis in Oregon, cont. Salmonellosis in Oregon, cont.
Salmonellosis in Oregon, cont. Salmonellosis in Oregon, cont.