Case Study – Outbreak at a Convention



Case Study – Outbreak at a Hotel Convention

PARTICIPANT VERSION

Objectives

• Describe case-control and cohort studies

• Choose the most appropriate study design for the given situation

• Create an outbreak questionnaire

• Create a table shell for a line listing

• Create an epi curve for an outbreak

• List the steps in an outbreak investigation

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 Carolina Center for Public Health Preparedness Web Site (), are recommended for Epi Team members without prior outbreak investigation experience. They can be viewed prior to completing the case study.

1. Embarking on an Outbreak Investigation (FOCUS on Field Epidemiology Volume 1, Issue 3)

2. Case Finding and Line Listing: A Guide for Investigators (FOCUS on Field Epidemiology Volume 1, Issue 4)

3. Epidemic Curves Ahead (FOCUS on Field Epidemiology Volume 1, Issue 5)

4. Selecting a Study Design (FOCUS on Field Epidemiology Volume 2, Issue 4)

5. Designing Questionnaires (I is for Investigation Session III)

Resources (Facilitator may print this document for participant reference)

Gastrointestinal Illness Quick Reference Guide ()

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Question 1: What diseases or infectious agents do you suspect, and what are their incubation periods? (You may use the Gastrointestinal Illness Quick Reference Guide available on the Epi Teams Training Web site.)

Question 2: Why is it helpful to consider the incubation period of possible diseases?

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Group Brainstorm

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

Question 3: What would you do next? Keep in mind the steps of an outbreak investigation.

Question 4: What activities should your environmental health specialist conduct at this time?

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Question 5: Now that you know the type of bacteria involved in the outbreak, how will you identify the specific food source of the outbreak?

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Question 6: Define case-control and cohort studies, and determine which would be more appropriate in this outbreak.

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Question 7: What is the best method of communicating with the conference attendees?

Question 8: What general types of information should you collect from the attendees?

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Activity

Draft an email questionnaire to send to all conference attendees about the outbreak. Be sure to include an introductory paragraph so attendees understand why they are requested to fill out the questionnaire.

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Activity

Using the information provided on the first 5 case-patients, create a line listing for the outbreak. You can use the table below to begin. The first two items, name and email address, are already filled in. Decide which other variables you would like to include in the remaining spaces. Then complete the table using the information in the previous update. Remember that a line listing may include demographic information, clinical information (signs and symptoms, lab results) and exposure information.

|Name |Email Address | | |

|11:00 AM |0 |0 |0 |

|12:00 PM |0 |0 |0 |

|1:00 PM |1 |0 |1 |

|2:00 PM |5 |1 |6 |

|3:00 PM |11 |1 |12 |

|4:00 PM |19 |5 |24 |

|5:00 PM |15 |3 |18 |

|6:00 PM |9 |1 |10 |

|7:00 PM |6 |0 |6 |

|8:00 PM |2 |0 |2 |

|9:00 PM |0 |0 |0 |

Draw epi curve on graph paper below.

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Question 10: Does the shape of the epi curve indicate a point source outbreak or a propagated outbreak? Remember that in a point source outbreak, everyone is exposed from the same source at the same time, while in a propagated outbreak disease transmission continues over time.

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Question 11: What recommendations would you make to the kitchen staff to reduce the chances of another Staph. aureus outbreak?

Question 12: You have just successfully conducted an outbreak investigation. Let’s review all of the steps of an outbreak investigation. List as many of these as you can.

Group Brainstorm

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?

• If a similar outbreak occurred in your county, do you think that your Epi Team would be prepared to handle it?

• Are there ways that you would have conducted the investigation differently than what was described?

• Why is it difficult to investigate an outbreak associated with a hotel?

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Background - August 24th

It is Wednesday afternoon at 4:30 pm, and you are getting ready to leave the county health department to start your weekend when the phone rings. The manager of the hotel and convention center across town, Hotel M, has called you because several dozen conference attendees have become sick, and he wants your help to deal with the situation.

When you arrive at Hotel M, the hotel manager takes you into his office to elaborate on the details. The hotel convention center recently hosted the Annual Association of Museum Curators Conference, which had 300 attendees. The conference lasted three days and ended today following a lunch buffet at noon and a final session at 3:00 pm.

A conference attendee called the front desk asking for a doctor at 2:00 pm. Three other attendees approached the front desk immediately after the first call and also reported illness. Throughout the next two hours, dozens more reported being ill. The major symptoms are nausea, vomiting, stomach cramps, and diarrhea.

Update – Thursday, August 25th, noon

Your initial interviews have not identified any suspect cases that were not conference attendees. You develop the following suspect case definition:

Any attendee of the museum curators conference with 2 or more of the following: vomiting, stomach cramps, nausea, or diarrhea, that began on Wednesday, August 24th.

The North Carolina Communicable Disease Control Branch recommends that you conduct a study to determine the specific food source of the Staph. aureus outbreak. You ask for and receive a list of all conference attendees. The list includes names, addresses, phone numbers, and email addresses for all 300 attendees.

Update – Sunday, August 28th

It is now Sunday, August 28th. The email response to your survey is very good: 96% of the email questionnaires are returned within 72 hours. The responses are compiled into one report, with information from 5 case-patients displayed below:

- Sarah Davis (sdavis@email), F, 11/8/50 had nausea, diarrhea and stomach pains, started feeling bad at 3 pm, and went through the buffet around 12:30 pm

- Ben Thomas (thomas@email), M, 2/15/61, had abdominal cramps, nausea, vomiting, and diarrhea which started at 4:30 pm and went through the buffet at noon

- Frank Cooper (frankc@email), M, 8/31/65 had nausea, vomiting, diarrhea beginning at 7:00 pm, went through buffet at 12:30 pm

- Janette Franklin (jrf@email), F, 1/4/46 had abdominal cramps and diarrhea which started at 2:30 pm, went through buffet at 12:00 pm.

- Susy Stoudemire (sstoude@email), F, 9/9/70, had abdominal cramps, nausea, and vomiting beginning at 4 pm, went through buffet at 12:30 pm

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Update – Thursday, August 25th, 10 am

The hospital laboratory tested stool samples for the 5 outbreak-related patients, and the tests came back positive for Staphylococcus aureus. You know that Staph. aureus is commonly spread through food that has been inadequately heated or refrigerated.

The environmental health portion of the investigation has revealed that some of the food warmers used by the hotel were defective, and did not maintain appropriate holding temperatures. Your environmental health specialist also finds out that yesterday’s lunch buffet was the largest that the hotel kitchen had ever prepared.

Update – Wednesday, August 29th

You and your Epi Team compare survey responses of people who became ill and those who did not, searching for common exposures among the cases that are not shared by those people who remained healthy.

Meanwhile, you receive laboratory results from environmental testing of leftover food from the lunch buffet. The pasta primavera tested positive for Staph. aureus.

Update – Wednesday, August 24th, 6 pm

Since this afternoon, 79 people have been reported ill at the hotel and 5 have been sent to the local hospital. All of the cases were attendees of the museum curators conference. Since the conference officially ended today, many of the conference attendees, including some that reported illness, have returned to their homes around the country.

You call the hospital to get information about the 5 patients who were admitted. All 5 are being treated with fluids. The hospital nurse tells you that stool specimens were collected from all 5 patients and sent to the hospital laboratory for analysis.

Update – Thursday, August 30th, 2007

The outbreak is over. All of the ill people have recovered, and you have provided guidance to the hotel kitchen staff about preventing future outbreaks. You and your Epi Team are meeting to discuss the investigation. You would like to talk about and document the aspects of the investigation that went well, and those that could have been improved.

Update – Friday, August 25th, 11 am

Since you have a complete list of conference attendees, you decide to conduct a cohort study. For this study, you will attempt to interview all conference attendees, including people who became ill and those who remained healthy. First you should determine how attendees will be contacted (e.g. phone, email, regular mail). Then, you need to create a questionnaire or modify an existing questionnaire.

Update

Because you have email addresses for all conference attendees, you decide to send an email questionnaire and follow-up via telephone with people who do not respond to the email.

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Museum curators

conference at Hotel M

4:30 First reported illness at Hotel M

Museum curators

conference at Hotel M

4:30- First reported illness at Hotel M

6:00- 79 people ill, 5 sent to the hospital; samples sent to hospital lab

4:30- First reported illness at Hotel M

6:00- 79 people ill,

5 go to the hospital; samples sent to hospital lab

Museum curators

conference at Hotel M

10:00- Lab results positive for Staph. aureus; food warmers found defective

12:00- List of conference attendees provided

10:00- Lab results positive for Staph. aureus; food warmers found defective.

12:00- List of conference attendees provided

4:30- First reported illness at Hotel M

6:00- 79 people ill,

5 go to the hospital; samples sent to hospital lab

Museum curators

conference at Hotel M

Surveys completed

August

Food handler tests positive for Staph aureus. Pasta primavera also positive

Surveys completed

10:00- Lab results positive for Staph aureus. Food warmers found defective.

12:00- List of conference attendees provided

4:30- First reported illness at Hotel M

6:00- 79 people ill,

5 go to the hospital. Samples sent to hospital lab

Curators and Archivists

Conference at Hotel M

Epi team debriefing

Curators and archivists

conference at Hotel M

4:30- First reported illness at Hotel M

6:00- 79 people ill,

5 go to the hospital; samples sent to hospital lab

10:00- Lab results positive for Staph. aureus; food warmers found defective.

12:00- List of conference attendees provided

Surveys completed

Pasta primavera tests positive for Staph. aureus.

August

August

August

August

August

August

Surveys completed

10:00- Lab results positive for Staph. aureus; food warmers found defective.

12:00- List of conference attendees provided

4:30- First reported illness at Hotel M

6:00- 79 people ill,

5 go to the hospital; samples sent to hospital lab

Curators and archivists

conference at Hotel M

Epi Team debriefing

4:30- First reported illness at Hotel M

6:00- 79 people ill,

5 go to the hospital; samples sent to hospital lab

10:00- Lab results positive for Staph. aureus; food warmers found defective.

12:00- List of conference attendees provided

Surveys completed

Pasta primavera tests positive for Staph. aureus.

August

Curators and archivists

conference at Hotel M

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