Case Study Outbreak at a Convention

Case Study – Outbreak at a Hotel Convention FACILITATOR 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 Convene your local Epi Team, and provide each Epi Team member with a copy of the case study (participant version). Choose one person to act as the facilitator. This person should use the facilitator’s version of the case study.

Guidance for facilitating the case study can be found on the next page. The case study begins on page 3.

Time Allotted: 1.5 hours

Background Materials The following trainings, found at the North Carolina Center for Public Health Preparedness Web Site (http://nccphp.sph.unc.edu/training/), 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 (http://nccphp.sph.unc.edu/epiteams/casestudies.htm)

1 Guidance for Facilitators

Goal The goal of working through a case study is active learning through engaged participation by each Epi Team member.

Role of Facilitator Reminder As a facilitator, your job is to: As the facilitator, you are the  Guide the Epi Team through the case study only team member with the  Involve every team member suggested answers to  Moderate discussion drawing on the discussion questions and suggested answers to discussion questions activities. Other Epi Team  Ensure key points are covered for each members have only the question scenario updates and questions.  Keep an eye on the clock

Active Participation All team members should be involved in the discussion. One strategy for getting everyone involved is to have team members take turns reading aloud and attempting to answer questions. Facilitators should: 1. Ensure that the room set-up encourages group participation, ie. everyone seated around a table or chairs in a circle. 2. Select one team member to read aloud the first update and the first question. 3. Encourage that team member to attempt to answer the first question (regardless of his/her background). 4. Encourage other team members to add information and discuss the question. 5. Use the suggested answers to cover key point(s) that were not addressed during the discussion. 6. Have the next person read aloud the next update or question and begin an attempted answer as above – move in sequence to include everyone. Follow this sequence until the scenario is completed, pacing discussion in order to finish the entire scenario.

Facilitation Tips  Read the case study ahead of time so you are prepared for the discussion.  Always remember the learning objectives for the case study.  If one person is dominating the conversation, call on other team members.  If someone in the group is not participating, ask his or her opinion.  When someone asks a question, encourage other team members to provide the answer.  Do not spend too much time providing the suggested answers to the group. Instead, encourage the team to share their opinions about possible responses to the given scenario.

2 3 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. 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.)

Suggested answer: Many gastrointestinal diseases have similar symptoms. However, there are a few pieces of information that are useful here. First, since no patients have fevers, you would have a lower index of suspicion for Salmonellosis and Shigellosis. Since the ill people came from all over the country, and have been together here for three days, it is unlikely that they were infected prior to that time. The sudden onset would lead you to suspect diseases with short incubation periods, including Staph. aureus (2-4 hours), Bacillus cereus (.5 – 24 hours), and norovirus (1-2 days). The symptoms do not seem as severe as might be expected with E. coli. You should also be looking for a disease with high transmissibility, since so many people became ill.

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

Suggested answer: The incubation period can help you to identify the disease agent. It appears this may be a point source outbreak, where all cases were exposed to a disease agent at about the same time while they were attending the conference. If the incubation period for a disease is longer than the 3 days that people have been at the conference, it is probably not the disease responsible for this outbreak. Likewise, once you have identified which disease is causing the outbreak, knowing the incubation period is very helpful in finding the source of the exposure.

4 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.

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.

Suggested answer: The first step of an outbreak investigation is to verify the diagnosis and confirm the outbreak. To do this you would call the hospital laboratory to get test results, or at least to find out when test results will be available. When you call the laboratory, you may also emphasize the importance of getting results quickly, since the ill people were part of a large outbreak. At this point, if you have not already called a meeting of your Epi Team, this would be a good time to do it. You should also report the outbreak to your Public Health Regional Surveillance Team (PHRST) and the NC Communicable Disease Control Branch.

The next step is to define a case and conduct case finding. To do this, it would be best to gather as much information as possible about the people who are ill. This information would include type of symptoms, time of symptom onset, lab tests conducted, and demographic information like age and gender, as well as any potential exposure information. You may be able to get some of this information while you are visiting the hotel if any of the ill people are still there. Once you have gathered this information, you can develop a working case definition, and begin looking for cases. You may work together with the Communicable Disease Control Branch and your PHRST to find cases. Some possible case finding strategies are listed below: 1) Get a list of all conference attendees and interview them; 2) Interview other hotel guests and staff;

5 3) Provide the case definition to local hospitals and health care providers using blast fax or email, and ask them to report suspect cases; and 4) Call laboratories to see if they have had an increase in test requests or positive results for any of the illnesses you suspect.

At this point, you might conduct other activities such as getting a list of foods that were served to conference attendees, finding out who prepared the meals for the conference (i.e. the hotel kitchen or an outside caterer), and preparing material for a press release.

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

Suggested answer: The environmental health specialist should visit the hotel kitchen, or whichever facility prepared food for the conference. During the visit (or during subsequent visits), the environmental health specialist should conduct the following activities: 1) Obtain menu of foods served to conference attendees, if this has not been done; 2) Inspect food preparation areas; 3) Observe food handling practices; 4) Collect samples of leftover food that was served to the conference attendees and then instruct kitchen staff to refrigerate remaining food until the investigation is complete, but not to serve it again; 5) Interview kitchen food handlers and other staff members to determine whether any have had symptoms of gastrointestinal illness in the recent past; 6) Provide education to food handlers and other kitchen staff about proper food handling practices, and infection control procedures; and 7) Advise kitchen managers about how to disinfect and clean the kitchen to ensure that no one else becomes ill.

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.

6 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?

Suggested answer: Staph. aureus has a short incubation period (2-4 hours), and so you would strongly suspect the lunch buffet as the source of the outbreak. To identify the specific food source, you should conduct interviews with everyone who ate at the buffet (including healthy people). Usually this is done by providing a list of food items (including beverages) and asking people whether they ate each item. You should also test leftover buffet food items and the kitchen equipment for Staph. aureus.

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.

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

Suggested answer: A case-control study compares a group of patients with a specific condition to a group of patients that do not have that condition. Case-control studies are frequently used in epidemiologic investigations because they can be conducted relatively cheaply and by a small number of people.

Cohort studies involve monitoring one specific group of people, grouped together due to some common characteristic. It is best to use a cohort study when there is a defined population at risk, and it is possible to get in touch with either every member of the cohort, or a representative sample.

7 In this situation, because you can limit the at-risk population to attendees at the conference, and you can get in touch with them via email, a cohort study is preferable.

Both types of studies are described in more detail in FOCUS on Field Epidemiology, Volume 2, Issue 4: Selecting a Study Design.

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.

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

Suggested answer: Because you need information quickly and the attendees are spread throughout the country, email is an acceptable format for contacting the attendees. An email questionnaire can allow you to quickly gather the information you need. Alternatively, you can contact the attendees by phone, but this would require more staff resources.

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

Suggested answer:  Demographic information: name, gender, date of birth  Clinical information: signs and symptoms, time of symptom onset, health care visits and medical diagnoses, laboratory tests and results  Epidemiologic information based on your hypothesis: which foods they ate (provide a list of all foods for attendees to choose from) and time they went through the buffet line

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.

8 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.

Sample email: You are being contacted as an attendee of the Annual Association of Museum Curators Conference held in Big City, North Carolina. There was an outbreak of Staphylococcus aureus (Staph. aureus), a non-life-threatening gastrointestinal illness, at the conference. If you did not become ill yesterday, it is unlikely that you will become ill. Whether you became ill or not, the Local Health Department needs your help to prevent other outbreaks. Please fill out the form below and return it via email to [email protected] AS SOON AS POSSIBLE, preferably by Monday, August 29th. You can type your answers directly beside the questions.

For more information about the outbreak, or to speak with someone at Local Health Department, call 1-800-000-000. For more information about Staph. aureus, visit the Centers for Disease Control and Prevention web site at http://www.cdc.gov/ncidod/dbmd/diseaseinfo/staphylococcus_food_g.htm.

Survey Form

Name: Sex: Date of Birth:

Have you had any of the following symptoms between Wednesday, August 22 and Friday, August 24? Please type Yes or No beside each symptom. Nausea Vomiting Stomach cramps Diarrhea Other NONE

If you had any symptoms, when did your first symptom begin? Please specify both the time and the date.

If you had any symptoms, did you seek medical attention? Please type yes or no. If yes, what was your diagnosis?

9 Did you eat the buffet lunch provided at the conference on August 24, 2007? Please type Yes or No.

If you ate the buffet lunch, please answer the following questions.

 What time did you go through the lunch buffet line? Please specify as close to the exact time as possible.

 Please indicate which foods you ate by typing Yes or No next to each food item.

o HERE INCLUDE A LIST OF ALL FOOD ITEMS THAT WERE IN LUNCH BUFFET

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

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

10 update. Remember that a line listing may include demographic information, clinical information (signs and symptoms, lab results) and exposure information.

Name Email Address Sarah Davis sdavis@email Ben Thomas thomas@email Frank Cooper frankc@email Janette Franklin jrf@email Susy sstoude@email Stoudemire

Suggested answer: Below is a sample line listing of ill people. Other variables may be included. Name Email Address Sex DOB N V D AC Time of Buffet Time Onset Line through buffet Sarah Davis sdavis@email F 11/8/50 1 0 1 1 3:00 1 12:30 Ben Thomas Thomas@email M 2/15/61 1 1 1 1 4:30 3 12:00 Frank Cooper frankc@email M 8/31/65 1 1 1 0 7:00 2 12:30 Janette Franklin jrf@email F 1/4/46 0 0 1 1 2:30 1 12:00 Susy Stoudemire sstoude@email F 9/9/70 1 1 0 1 4:00 3 12:30 N = nausea, V = vomiting, D = diarrhea, AC = abdominal cramps

Activity After creating a full line listing of all 79 case-patients, you count the number of case- patients by hour of symptom onset. Cases are classified as “suspect” based on the case definition you created, and “confirmed” if they also have positive laboratory results. Using the data summary below, create an epi curve to show the frequency of cases over time. You may want to have one of your Epi Team members draw the epi curve on a flip chart, or use the graph below. Note: you will want to set your x-axis scale to hours instead of days.

Suspect Confirmed Total Time Cases Cases Cases 11:00 AM 0 0 0 12:00 PM 0 0 0

11 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.

12 A U G U S T 22 23 24 25 26 27 28 29 30

10:00- Lab results positive for Surveys Curators and archivists 4:30- First reported Staph. aureus; food warmers completed conference at Hotel Millness at Hotel M found defective. 6:00- 79 people ill, 12:00- List of conference 5 go to the hospital; attendees provided samples sent to hospital lab

Suggested answer: Below is the suggested answer for the epi curve. It is useful to label the time of the lunch buffet, since it is the presumed source of the outbreak.

Epi Curve - Staph. aureus Cases, Hotel M August 24, 2007

30 Suspect Cases 25

s Confirmed Cases e s

a 20 C

f o 15 r e

b Lunch Buffet

m 10 u N 5

0 11:00 12:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 8:00 9:00 AM PM PM PM PM PM PM PM PM PM PM Time

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.

Suggested answer: This epi curve is a classic point source outbreak. Point source outbreaks are characterized by a sharp upward slope and gradual downward slope as is shown in the epi curve here.

13 A U G U S T 22 23 24 25 26 27 28 29 30

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.

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

Suggested answer: According to the North Carolina Communicable Disease Manual, foodhandlers should be educated about the following preventive measures: 1. Strict food hygiene, sanitation, and cleanliness of kitchens, proper temperature control, handwashing, cleaning of fingernails, etc. 2. The dangers of working with exposed skin, nose, or eye infections and uncovered wounds. 3. Reducing food handling time (initial preparation to serving) to the absolute minimum, with no more than 4 hours at ambient temperature. Keep perishable foods hot (great than 70° C/158° F) or cold (<10° C/50° F; best is <4° C/39° F) in shallow containers and covered, if they are to be stored for more than 2 hours. 4. Do not partially cook meat and poultry one day and reheat the next, unless it can be stored at a safe temperature. 5. Large cuts of meat should be thoroughly cooked; for more rapid cooling of cooked foods, divide stews and similar dishes prepared in bulk into many shallow containers and place in rapid chiller. 6. Temporarily exclude people with boils, abscesses and other purulent lesions of hands, face, or nose from foodhandling. 7. Symptomatic foodhandlers should also be excluded until asymptomatic. Additional education for the kitchen staff on sanitation could also be a useful tool in preventing future outbreaks.

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.

Suggested answer: Although this list is ordered, in an actual outbreak, you may complete some tasks at the same time, or in a different order. 1. Verify diagnosis and confirm outbreak 2. Define a case and conduct case finding

14 A U G U S T 22 23 24 25 26 27 28 29 30

3. Tabulate and orient date: time, place, person (e.g. creating line listings and epi curves) 4. Take immediate control measures (e.g. includes removing the source of the outbreak, taking steps to prevent further disease transmission, and educating the affected population) 5. Formulate and test hypothesis 6. Plan and execute additional studies 7. Implement and evaluate control measures 8. Communicate findings

15 A U G U S T 22 23 24 25 26 27 28 29 30

10:00- Lab results positive for Surveys Epi Team Curators and archivists 4:30- First reported Staph. aureus; food warmers completed debriefing conference at Hotel Millness at Hotel M found defective. 6:00- 79 people ill, 12:00- List of conference Pasta primavera tests positive 5 go to the hospital; attendees provided for Staph. aureus. samples sent to hospital lab

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.

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?