Activity: SOME CLEVER TITLE HERE



Case Study: Gastrointestinal Illness on a College Campus

FACILITATOR VERSION

Objectives

• List three active case finding strategies for a gastrointestinal outbreak on a college campus

• Create a case definition, given an outbreak scenario

• Describe the purpose of initial interviews with case-patients

• Identify the responsibilities of the environmental health specialist during a foodborne 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 (), 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. Designing Questionnaires (I is for Investigation Session III)

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

4. Case-Control Studies for Outbreak Investigations (FOCUS on Field Epidemiology Volume 3, Issue 2)

Resources

Foodborne Disease Surveillance and Outbreak Investigation Toolkit, CDC



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

As a facilitator, your job is to:

• Guide the Epi Team through the case study

• Involve every team member

• Moderate discussion drawing on the suggested answers to discussion questions

• Ensure key points are covered for each question

• 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.

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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 1: What questions do you ask Sheila during this phone call?

Suggested answer: Ask questions in the following categories:

1) Contact information for the person making the report (Sheila);

2) Contact information for the ill persons;

3) Total number of people that have been ill and characteristics of the ill people (e.g. are they all male? All freshmen? Both staff and students?);

4) Usual number of cases of GI illness that the Student Health Services would typically expect at this time of year;

5) Specific symptoms;

6) Any diagnoses and treatment;

7) Recent events on campus where large groups of students were gathered; and

8) Any common factors or connections that Sheila has noticed among the cases.

Also remember to ask Sheila for her theory about what is going on. Since she is familiar with the students and the campus, she may think of a potential cause of the outbreak that you would not have considered.

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Question 2: What diseases would you suspect at this point?

Suggested answer: At this early point, you would suspect virtually any gastrointestinal illness, including Salmonella, Shigella, norovirus, Campylobacter, Yersinia, E. coli O157, Bacillus cereus, and Staphylococcus aureus. You would contact the hospital to find out whether any students had positive laboratory results for any of these diseases.

Question 3: What, if any, clinical specimens should be collected from the ill students? Who is responsible for collecting the specimens? Where should the specimens be sent?

Suggested answer: Stool samples should be collected from the ill students and sent to a laboratory capable of testing for a wide range of gastrointestinal pathogens, including Salmonella, Shigella, norovirus, Campylobacter, Yersinia, E. coli O157, Bacillus cereus, and Staphylococcus aureus. The Student Health Service at the college may be able to collect stool samples from some of the ill students. Otherwise, the responsibility would lie with your local health department. Since a few of the students went to the hospital, you should also call the hospital to determine whether any laboratory tests have already been conducted. Here in North Carolina, the stool samples would likely be sent to the State Laboratory of Public Health, one of the regional laboratories in Asheville, Greenville, or Charlotte, or a private laboratory. If a stool sample is not available for every student, it may be possible to collect a vomitus sample.

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Question 4: Of the diseases listed above, norovirus is the only one which is not routinely tested by the North Carolina State Laboratory of Public Health (SLPH) when stool samples are submitted. However, SLPH does have the capacity to test for norovirus. What steps should you take to ensure that the specimens are tested for norovirus?

Suggested Answer: First, you should call the Communicable Disease Control Branch at the NC Division of Public Health. There are two reasons to call: 1) to report the possible outbreak, and 2) to authorize testing for norovirus, since the local health department cannot authorize such testing. Next, you need to be sure that at least 5 specimens are collected, since SLPH will not test for norovirus with less than 5 specimens. Finally, be sure to write “outbreak” on the laboratory submittal slip to ensure that testing is rapid.

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Question 5: What specific actions will you take to determine whether there are other possible cases? Discuss which Epi Team members will be responsible for each case finding task.

Suggested answer: First you will create a working case definition based on the information provided by Sheila. Next, you should conduct active case finding, using one or more of the following strategies:

1) Call the hospital where the students were sent to determine whether there are additional cases from Madison College;

2) Talk to the ill people and find out if they know other people who have gotten ill;

3) Call local laboratories to find out if they have had an increase in testing requests for gastrointestinal (GI) pathogens;

4) Contact other healthcare providers in the area to determine if they have seen increased number of people with GI illness;

5) Send an email to the entire campus of Madison College (including students, faculty, and staff) asking them to visit Student Health Services if they have gastrointestinal symptoms. (This email would also be a good place to provide some infection control guidance);

6) Set up a hotline for people to call if they have symptoms of illness;

7) Send resident assistants to visit all dormitory residents to ensure that very ill students are not isolated in their rooms, and consider ways to do the same for students living in sorority and fraternity houses on campus; and

8) Call other local colleges to notify them of the outbreak and find out whether they have observed similar cases.

The Epi Team member who is responsible for each case finding activity will differ by local health department. You may want a single Epi Team member to be a liaison between Madison College and your health department.

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Activity

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 clinical information, and elements related to person, place, and time.

|Clinical Information (e.g. disease signs and symptoms, lab | |

|results) | |

|Person | |

|Place | |

|Time | |

Suggested answer: At the beginning of an outbreak, it is usually best to create a broad case definition that will capture all possible cases.

One suggested case definition is included below:

|Clinical Information (e.g. disease signs and symptoms, lab |Vomiting or diarrhea (3 or more loose stools in a 24 hour period)|

|results) | |

|Person |Anyone affiliated with Madison College (including students, |

| |faculty, staff, and visitors) |

|Place |Madison College |

|Time |Symptom onset between March 9 and present |

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Question 6: What is the purpose of these initial interviews?

Suggested answer: The purpose of the early interviews is to generate one or more hypotheses about potential sources of disease exposure. The hypothesis-generating interviews do not need to be conducted with all of the case-patients, but rather with a subset. Ideally, these initial interviews will allow you to narrow down the potential sources of exposure, create a plausible hypothesis, and then conduct hypothesis-testing interviews with both ill and healthy persons to determine whether or not the hypothesis is correct.

Question 7: Will you create a new questionnaire specifically for this outbreak, or will you use an existing questionnaire? If you choose to use an existing questionnaire, please discuss where this questionnaire is located, and how it will need to be modified for this outbreak.

Suggested answer: Although you do not yet know the cause of the outbreak, most GI illnesses result from exposure to contaminated food or water. You should obtain a food history and gather information about water exposure. You may want to start by using a standardized foodborne illness questionnaire for hypothesis-generating interviews. Keep in mind that you may need to add or subtract specific questions as appropriate. Once you have a better idea of possible sources, you will refine this questionnaire, or create a new questionnaire based on the suspected sources of infection.

Two standard questionnaires for foodborne disease outbreaks can be found in the Foodborne Disease Surveillance and Outbreak Investigation Toolkit from the Centers for Disease Control and Prevention ().

Question 8: Should your health department activate its Incident Command System (ICS) at this time? If so, who is responsible for activating the ICS?

Suggested answer: Yes, it is probably a good idea to activate the Incident Command System for several reasons. First, there are at least 29 cases, which represent a rather large outbreak. Second, this is a good opportunity to practice using the ICS and to work out problems or kinks in the system. The purpose of the ICS structure is to facilitate effective emergency management across multiple agencies and jurisdictions. For a local health department, the ICS structure can be used to deal with disease outbreaks. The person responsible for activating the ICS structure may vary, but is often the local Health Director.

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Question 9: What actions will your environmental health specialist take in response to this information?

Suggested answer: Sanitarians and/or environmental health specialists should visit the student union cafeteria as soon as possible and take the following actions:

1) Inspect kitchen facilities and observe food handling practices;

2) Collect samples from the salad bar, deli sandwiches, and sweet tea;

3) Determine whether any of the food from March 9th and 10th is available – instruct staff not to discard those items;

4) Recommend thorough cleaning and maintenance of all cafeteria and kitchen facilities while students are away on spring break;

5) Interview staff members to determine whether any have been ill;

6) Collect stool samples from food handlers; and

7) Educate kitchen staff about handwashing, maintaining foods at proper temperatures, and regularly disinfecting kitchen facilities.

Question 10: Is it time to conduct a case control or a cohort study? If so, which type of study design will you use? Explain your answer.

Suggested answer: Yes, it is appropriate to conduct a case control study at this time. Case control studies are best when it is difficult to identify every person who may have become ill, or when your time and resources are limited. A cohort study is the best choice when it is easy to identify everyone who may have become ill (e.g. all attendees at a wedding reception or all students in a single classroom), and there are enough resources to interview everyone. In this situation, a case control study is best because it would be very difficult to track down every student who ate in the student union cafeteria on March 9th and 10th, and there would probably be too many students to interview. Instead, by conducting a case control study, you will only need to interview the ill students and a sample of healthy students (controls). If possible, it would be ideal to identify and contact some controls before the weekend, when it will become more difficult to reach students on spring break.

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Question 11: Based on the laboratory results, what infection control measures would you recommend?

Suggested answer: Norovirus is highly infectious, so there is certainly the possibility of secondary transmission. You and your Epi Team should consider appropriate infection control measures, which may include:

1) Sending reminders to the entire college community about the importance of handwashing with soap and water;

2) Providing a norovirus fact sheet to the college community;

2) Excluding foodhandlers from work if they have been ill in the past 72 hours; and

3) Recommending thorough disinfection of all cafeteria facilities.

Note that these infection control measures are not specific to norovirus, but rather are applicable to many foodborne diseases. It is not necessary to wait for laboratory confirmation of the exact pathogen before instituting disease control measures. You probably would have begun many of these control measures early in the outbreak.

Question 12: What activities, if any, is your health educator conducting at this time?

Suggested answer: This is an ideal time for your health educator to provide information to people at Madison College about prevention of norovirus and other foodborne illnesses. The best way to share this information depends upon the specific setting, but you may consider the following:

1) Sending an email announcement to the college community with facts about norovirus, including prevention strategies such as handwashing;

2) Posting flyers in public restrooms and eating areas reminding people about the importance of handwashing;

3) Asking the student newspaper to write an article about foodborne illness;

4) Posting norovirus fact sheets or brochures at Student Health Services; and

5) Posting information about norovirus and other foodborne illnesses to college and health department websites.

In addition to educating the college community, this outbreak provides a good opportunity to educate the community at large, so consider strategies that will reach a larger audience as well.

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Question 13: Should you attempt to contact Marcia again? Why or why not? Are there confidentiality issues that you should consider?

Suggested answer: Yes, it is probably wise to try to speak with Marcia one more time, perhaps in an environment where she is more comfortable. It would be good to get a stool sample if possible, ask again about symptoms of illness, and determine whether she has close contacts who have been ill. However, keep in mind the importance of maintaining confidentiality in this situation.

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Question 14: How do you interpret these findings overall? After describing the findings generally, interpret the odds ratio for deli roast beef. Remember, an odds ratio is the odds of exposure among cases divided by the odds of exposure among controls.

Suggested answer: The data show that overall, the odds of eating deli ham, turkey, or roast beef were significantly higher among cases compared to controls. The odds of eating the salad bar items (lettuce, tomatoes, cucumbers, onions, green peppers) are not significantly different between cases and controls. The significant odds ratios for the deli meats may lead us to suspect the deli meats as a source of disease. The interpretation of the odds ratio for deli roast beef is: Cases were 2.66 times more likely to have eaten deli roast beef than controls. (For more information on calculating and interpreting odds ratios, see the FOCUS issue “Case-Control Studies for Outbreak Investigations” listed in the background materials.)

Odds ratio = 1: odds of exposure are the same among cases and controls (no association between exposure and disease)

Odds ratio > 1: odds of exposure are greater among cases than controls (a positive association between exposure and disease)

Odds ratio < 1: odds of exposure are less among cases than controls (a negative, or protective, association between exposure and disease)

After we look at the odds ratio itself, it is important to examine the confidence interval (CI). The CI tells us how precise our odds ratio is. A good rule of thumb is: an odds ratio is significant if the confidence interval does not overlap 1. For the deli roast beef, the confidence interval is 1.13-6.30. Since the lower bound is 1.13, the confidence interval does not overlap 1, and the odds ratio for deli roast beef indicates a significant association between exposure (eating roast beef) and disease (norovirus).

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Question 15: Is your outbreak investigation complete? Why or why not?

Suggested answer: The investigation is not complete. There are several goals to an outbreak investigation, including identifying cases for treatment, stopping disease transmission, identifying the source of infection, and preventing future outbreaks. Based on the interview data, you can confidently identify the deli meat as the source of infection. You suspect that Marcia’s baby was ill with norovirus, and that Marcia contaminated the deli meats after changing the baby’s diaper. However, you probably will never have conclusive evidence of the chain of transmission, since you were unable to collect a stool specimen from the infant until two weeks after her symptoms ended.

Still, it may be worth investigating contacts of the infant to find out if transmission occurred at other sites (e.g. daycares).

It also appears as though the cycle of disease transmission at Madison College has ended, since Student Health Services has not reported additional cases of GI illness.

The remaining tasks, then, relate to prevention of future outbreaks. It is important to write an outbreak report that summarizes your investigation. This report should be submitted to your supervisor and the director of your local health department. You should work with your health director to ensure that Madison College and the state health department each receive the outbreak report, or a summary of the investigation, results, and control measures.

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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?

• 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?

• What are the challenges of investigating an outbreak on a college campus?

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Reminder

As the facilitator, you are the only team member with the suggested answers to discussion questions and activities. Other Epi Team members have only the scenario updates and questions.

Background

It is 9 am on Wednesday, March 11th, and you are busy with the routine work of your local health department. You receive a call from Sheila Patterson, a nurse with Student Health Services at Madison College. Madison is a local college with approximately 7,000 undergraduate students. Sheila tells you that an unusual number of students have presented at the clinic with gastrointestinal (GI) illness over the past 24 hours. Primary symptoms are vomiting and diarrhea, with some students also reporting abdominal cramps and fever. Three of the students were so ill that they were sent to nearby Memorial Hospital for evaluation.

Update 1

Sheila tells you a total of 14 students had GI symptoms yesterday, and another 4 presented to their clinic this morning. She tells you some students called the Student Health Services office after hours and were instructed to go to the hospital if their symptoms were serious.

Update 2

You recommend to Sheila that stool specimens be collected from as many ill students as possible, and sent to the State Laboratory of Public Health for analysis. You offer to call the laboratory to let them know that the specimens will be arriving, and should be batched together to test for several possible pathogens, including Salmonella, Shigella, norovirus, Campylobacter, Yersinia, and E. coli O157.

Update 3

After getting Sheila’s contact information, you hang up the phone, and think about the next steps that you should take. You think it would be wise to determine whether there are other possible cases of GI illness in the college community.

Update 4

It is now 8 am on Thursday, March 12th, and you have a better sense of the scope of the outbreak. You called the infection control practitioner at Memorial Hospital yesterday, and he reported the hospital had seen at least 6 Madison College students presenting with GI illness. Sheila also called back this morning with an update – there were a total of 9 cases of GI illness at Student Health Services yesterday. Also, she forgot to mention yesterday that the students are going on spring break next week, so it will be difficult to get in touch with them after Friday.

You realize that you and your Epi Team will have to act quickly to determine the source of the outbreak. Here is a brief summary of what you know so far.

Number of possible cases: 29 (23 reported from Student Health Services, 6 from Memorial Hospital)

Dates of onset: 3/9 - present

Primary Symptoms: vomiting and diarrhea

Update 5

Although you do not know the disease pathogen, you would like to conduct preliminary interviews with some of the case-patients. You have obtained contact information for 22 of the 29 people who are known to be ill, and you decide to start by talking with as many of the case-patients as possible.

Update 6

It is Friday morning, March 13th, and there are now a total of 47 suspected cases. Yesterday you were able to conduct interviews with 9 case-patients. All of them ate at the student union cafeteria on March 9th or 10th, and common food items included salad from the salad bar, deli sandwiches, and sweet tea.

Update 7

You and your Epi Team work quickly to begin conducting a case-control study. Because all of the case-patients ate at the student union cafeteria on March 9th or 10th, you decide that controls should be people who also ate in the student union cafeteria on the same days but did not become ill. To identify controls, you obtain a list of students and phone numbers from the Registrar’s Office, and ask case-patients about roommates and people who ate in the cafeteria with them but did not become ill. With assistance from your Public Health Regional Surveillance Team, you begin conducting phone interviews in the afternoon. By the end of the day, you have completed interviews with a total of 35 people, of whom 21 are eligible to be controls.

The State Laboratory of Public Health calls to tell you that it received a total of 19 stool samples, all of which were negative for Salmonella, Shigella, Campylobacter, Yersinia, E. coli O157, Bacilius cereus, and Staph. aureus. Of the 19 samples, 15 tested positive for norovirus using RT-PCR (real-time polymerase chain reaction).

Update 8

During spring break (March 16-20), you and your team have little success interviewing additional controls, since most students are out of town. However, the environmental health specialist on your team is busy ensuring that the student union cafeteria is thoroughly disinfected and collecting samples from remaining food items.

You are able to interview all of the 15 foodhandlers who work in the cafeteria and all 15 deny any symptoms of illness in the 7 days prior to the outbreak. All but one foodhandler agree to submit stool samples for testing. The person who refuses to submit a stool sample, Marcia, is then fired by the cafeteria manager. Marcia’s responsibilities included slicing deli meats and making deli sandwiches.

Update 9

It is now Tuesday, March 24th, two weeks after the first case of norovirus. The students returned to class on Monday after spring break. Sheila Patterson, the nurse from Student Health Services, says that she hasn’t seen any additional cases of GI illness since the beginning of spring break.

Over the last 3 days , you and your Epi Team conducted interviews with all but one of the suspect cases, and additional controls. You now have food recall data from a total of 46 cases and 75 controls. You decide to analyze the data to determine whether any one food item is associated with illness.

Here are some of your findings:

Food Item |Cases

(N = 46) |Controls

(N = 75) |Odds Ratio |Confidence Interval |P value | |Lettuce |31 |46 |1.30 |0.56-3.03 |0.50 | |Tomatoes |20 |30 |1.15 |0.51-2.59 |0.71 | |Cucumbers |26 |31 |1.85 |0.82-4.15 |0.10 | |Onions |6 |13 |0.72 |0.22-2.24 |0.53 | |Green peppers |19 |28 |1.18 |0.52-2.68 |0.66 | |Deli ham |24 |24 |2.32 |1.02-5.30 |0.03 | |Deli turkey |30 |32 |2.52 |1.10-2.80 |0.02 | |Deli roast beef |21 |18 |2.66 |1.13-6.30 |0.01 | |

Update 10

Based on the initial results of your analysis, you calculate one more odds ratio, for people who ate any deli sandwich. The results are below.

Food Item |Cases

(N = 46) |Controls

(N=75) |Odds Ratio |Confidence Interval |P value | |Any deli sandwich |41 |33 |10.44 |3.3-33.96 | ................
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