Case Study: Hepatitis A Cluster with Unknown Source

PARTICIPANT VERSION

Objectives

  • List the steps in an outbreak investigation
  • List sources of data within the local health department
  • Interpret surveillance data
  • Choose an appropriate public health response based upon interpretation of surveillance data
  • Define the Incident Command System and identify triggers for activating it
  • Create a table shell for a line listing

Instructions

Read each update aloud and, as a team, discuss the questions that follow.

Time Allotted: 1.5 hours

Background Materials

The following trainings, found at the North CarolinaCenter for Public Health Preparedness Training Web site ( are recommended for Epi Team members without prior outbreak investigation experience. They can be viewed prior to completing the case study.

  1. An Overview of Outbreak Investigations(FOCUS on Field Epidemiology Volume 1, Issue 1)
  2. Federal Public Health Surveillance and Analysis of Surveillance Data(E is for Epi Session 4.2)
  3. Case Finding and Line Listing: A Guide for Investigators(FOCUS on Field Epidemiology Volume 1, Issue 4)
  4. Incident Command System (ICS) for Public Health

Resources

Centers for Disease Control and Prevention. Hepatitis A Fact Sheet. 2007. Available at

Centers for Disease Control and Prevention. Update: prevention of Hepatitis A after exposure to Hepatitis A virus and in international travelers. MMWR Morb Mortal Wkly Rep 2007;56:1080-1084.

Heymann DL, ed. Control of Communicable Diseases Manual. 18th ed. WashingtonDC, USA: American Public Health Association; 2004.

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Question 1: What is the first step in an outbreak investigation?

Question 2: How could disease surveillance data be useful during this investigation? Why is it important to perform surveillance on diseases like hepatitis A?

Question 3: Where should you look for baseline surveillance data about hepatitis A in CountyKand throughout North Carolina?

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Question 4: Based on this information, do you think the 3 cases in your county represent an outbreak?

Question 5: At this point, should you contact any other public health agencies? If so, which ones?

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Question 6: What do you know about hepatitis A that will help you in your investigation?Complete the chart below with disease information. Hint: You do not need to memorize all of this information. Instead, consult the Control of Communicable Diseases Manual.

Hepatitis A Facts

Symptoms
Incubation Period
Mode of Transmission
Duration of Illness
Diagnosis
Treatment
Other

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Question 7: After verifying the diagnosis and confirming the outbreak, what are the next stepsthat you should take in this outbreak investigation?

Question 8: Do you recommend any public health control measures? If so, please describe appropriate control measures.

Activity

Defining a case is an important step in an outbreak investigation. Case definitions provide a simple, uniform way to determine who should be considered a case and who should not. As a team, decide upon an initial (working) case definition. Keep in mind that your case definition will change as you obtain more information. A case definition should always include both clinical information and elements related to person, place, and time.

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Clinical Information (e.g. disease signs and symptoms, lab results)
Person
Place
Time

Question 9: What is the purpose of ICS?

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Group Brainstorm

Choose one member of your Epi Team to record responses on a flip chart. As a group, discuss the following question.

Question 10: Generally, what are some triggers for activating ICSin your health department?

Question11: If you were the environmental health specialist, what water sources/environmental specimenswould you collect for hepatitis A testing?

Question 12: Should you offer hepatitis A vaccine and/or immune globulin (IG) to the wife and child of the farm owner? Why or why not?

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July / 16 / 17 / 18 / 19 / 20 / 21 / 22 / 23 / 24 / 25 / 26 / Sept

Question 13: Are you concerned that the produce grown on the farm could be a source of hepatitis A transmission? Why or why not? If so, do you make any recommendations about the produce?

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Question14: You would like to interview these contactsto find out if they’ve been sick. What are some strategies that you can use to find these individuals?

Question 15: What actions should you take now?

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Question 16: How should you organize information about the cases?

Group Brainstorm

Choose one member of the Epi Team to record responses on a flip chart. As a group, discuss the following question.

Question 17: The Incident Commander has requested that your Epi Team create a line listing of the 19 cases. What information would you include inthe line listing?

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Group Brainstorm

Often, after an outbreak investigation, an Epi Team reviews the investigation in a “hot wash” or after-action review. The questions below are examples of questions that could be used in such a review. Choose one member of the Epi Team to record responses on a flip chart. As a group, discuss one or more of the following questions.

  • What aspects of the investigation were successful?
  • All outbreaks present unique challenges. What characteristics of this outbreak made it challenging?

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  • What areas of the investigation could have been improved?
  • If a similar outbreak occurred in your county, do you think that your Epi Team would be prepared to handle it?

References

Moore Z. Trip Report: Hepatitis A Outbreak, MadisonCounty, NC, 2006.

Moore Z, Sobsey M, Ganova-Raeva L, et al. Hepatitis A associated with contaminated spring water -- North Carolina, 2006. Poster presented at the Infectious Diseases Society of America 45th Annual Meeting; October 4-7, 2007; San Diego, CA.

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