Gastroenteritis at a University in Texas 

STUDENT’S VERSION

Original investigators: Nicholas A. Daniels,1 David A. Bergmire-Sweat,2 Kellogg J. 

Schwab,3 Kate A. Hendricks,2 Sudha Reddy,1 Steven M.. Rowe,1 Rebecca L. Fankhauser,1,4 

Stephan S. Monroe,1 Robert L. Atmar,3 Roger I. Glass,1 Paul S. Mead,1 Ree A. CalmesSlovin,5

 Dana Cotton,6 Charlie Horton,6 Sandra G. Ford,6 Pam Patterson6

1

Centers for Disease Control and Prevention, 2Texas Department of Health, 3Baylor College of 

Medicine, 4Atlanta Veterans Administration Medical Center, 5City of Huntsville, Health 

Inspections, 6Texas Department of Health, Region 6/5S 

Case study and instructor’s guide created by: Jeanette K. Stehr-Green, MD

NOTE: This case study is based on a real-life outbreak investigation undertaken in 

Texas in 1998. Some aspects of the original outbreak and investigation have been 

altered, however, to assist in meeting the desired teaching objectives and allow 

completion of the case study in less than 3 hours. 

Students should be aware that this case study describes and promotes one particular 

approach to foodborne disease outbreak investigation. Procedures and policies in 

outbreak investigations, however, can vary from country to country, state to state, and 

outbreak to outbreak.

It is anticipated that the epidemiologist investigating a foodborne disease outbreak will 

work within the framework of an “investigation team” which includes persons with 

expertise in epidemiology, microbiology, sanitation, food science, and environmental 

health. It is through the collaborative efforts of this team, with each member playing a 

critical role, that outbreak investigations are successfully completed. 

We invite you to send us your comments about the case study by visiting our website at 

http://www.phppo.cdc.gov/phtn/casestudies. Please include the name of the case study 

with your comments.

April 2002 

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES 

Public Health Service 

Centers for Disease Control and Prevention 

Atlanta, Georgia 30333 
STUDENT’S VERSION

Gastroenteritis at a University in Texas

Learning objectives:

After completing this case study, the student should be able to:

1. list categories and examples of questions that should be asked of key informants who

report a suspected outbreak of foodborne disease 

2. list four criteria for prioritizing the investigation of suspected foodborne disease

outbreaks 

3. list three common pitfalls in the collection of clinical specimens for the investigation

of suspected foodborne diseases

4. determine the most efficient epidemiologic study design to test a hypothesis (including

the case definition and the appropriate comparison group)

5. describe the advantages and disadvantages of different forms of questionnaire

administration (e.g., self-administered, telephone, in-person)

6. list key areas of focus in interviewing foodhandlers and observing kitchen practices in

a foodborne disease outbreak

PART I - OUTBREAK DETECTION

On the morning of March 11, the Texas Department of Health (TDH) in Austin received a

telephone call from a student at a university in south-central Texas. The student reported that he

and his roommate, a fraternity brother, were suffering from nausea, vomiting, and diarrhea. 

Both had become ill during the night. The roommate had taken an over-the-counter medication

with some relief of his symptoms. Neither the student nor his roommate had seen a physician or

gone to the emergency room.

The students believed their illness was due to food they had eaten at a local pizzeria the previous

night. They asked if they should attend classes and take a biology mid-term exam that was

scheduled that afternoon.

Question 1: What questions (or types of questions) would you ask the student?
Gastroenteritis at a University in Texas

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Question 2: What would you advise the student about attending classes that day?

The “Foodborne Illness Complaint Worksheet” (Appendix 1) was completed based on the call. 

The student refused to give his name or provide a telephone number or address at which he or

his roommate could be reached.

Question 3: Do you think this complaint should be investigated further? 
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TDH staff were skeptical of the student’s report but felt that a minimal amount of exploration

was necessary. They began by making a few telephone calls to establish the facts and determine

if other persons were similarly affected. The pizzeria, where the student and his roommate had

eaten, was closed until 11:00 A.M. There was no answer at the University Student Health

Center, so a message was left on its answering machine.

A call to the emergency room at a local hospital (Hospital A) revealed that 23 university 

students had been seen for acute gastroenteritis in the last 24 hours. In contrast, only three

patients had been seen at the emergency room for similar symptoms from March 5-9, none of

whom were associated with the university.

At 10:30 A.M., the physician from the University Student Health Center returned the call from

TDH and reported that 20 students with vomiting and diarrhea had been seen the previous day. 

He believed only 1-2 students typically would have been seen for these symptoms in a week. 

The Health Center had not collected stool specimens from any of the ill students.

Question 4: Do you think these cases of gastroenteritis represent an outbreak at the university? 

Why or why not?
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PART II - INITIAL MICROBIOLOGIC INVESTIGATION

On the afternoon of March 11, TDH staff visited the emergency room at Hospital A and

reviewed medical records of patients seen at the facility for vomiting and/or diarrhea since

March 5. Based on these records, symptoms among the 23 students included vomiting (91%),

diarrhea (85%), abdominal cramping (68%), headache (66%), muscle aches (49%), and bloody

diarrhea (5%). Oral temperatures ranged from 98.8/F (37.1/C) to 102.4/F (39.1/C) (median:

100/F [37.8/C]). Complete blood counts, performed on 10 students, showed an increase in white

blood cells (median count: 13.7 per cubic mm with 82% polymorphonuclear cells, 6%

lymphocytes, and 7% bands). Stool specimens had been submitted for routine bacterial

pathogens, but no results were available.

Question 5: List the broad categories of diseases that must be considered in the differential

diagnosis of an outbreak of acute gastrointestinal illness.

Question 6: How might you narrow the range of agents suspected of causing the gastrointestinal

illness?
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TDH staff asked health care providers from the University Student Health Center, the Hospital A

emergency room, and the emergency departments at six other hospitals located in the general

vicinity to report cases of vomiting or diarrhea seen since March 5. A TDH staff person was

designated to help the facilities identify and report cases. The health care providers were also

asked to collect stool specimens from any new cases. Bacterial cultures from patients seen in

the emergency rooms were to be performed at the hospital at which they were collected and

confirmed at the TDH Laboratory. Specimens collected by the Student Health Center were to be

cultured at the TDH Laboratory.

Question 7: What information should be provided with each stool specimen submitted to the

laboratory? How will the information be used?

Question 8: How should specimens be transported from the University Health Center to the

TDH laboratory?
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Later that afternoon, preliminary culture results from 17 ill students became available. The

specimens, collected primarily from the emergency room at Hospital A on March 10, did not

identify Salmonella, Shigella, Campylobacter, Vibrio, Listeria, Yersinia, Escherichia coli

O157:H7, Bacillus cereus, or Staphylococcus aureus. Some specimens were positive for fecal

leukocytes and fecal occult blood.

Question 9: How might you interpret the bacterial culture results? What questions do these

results raise?
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PART III - DESCRIPTIVE EPIDEMIOLOGY AND HYPOTHESIS GENERATION

By March 12, seventy-five persons with vomiting or diarrhea had been reported to TDH. All

were students who lived on the university campus. No cases were identified among university

faculty or staff or from the local community. Except for one case, the dates of illness onset were

March 9-12. (Figure 1) The median age of patients was 19 years (range: 18-22 years), 69%

were freshman, and 62% were female.

Figure 1. Onset of gastroenteritis among students, University X, Texas, March 1998. (N=72) (Date of

onset was not know n for three ill students.)
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TDH staff met with the Student Health Center physician and nurse, and several university

administrators including the Provost. City health department staff participated in the meeting.

Question 10: What topics would you include in discussions with university officials?
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TDH and City Health Department staff gathered the following information:

The university is located in a small Texas town with a population of 27,354. For the

spring semester, the university had an enrollment of approximately 12,000 students;

2,386 students live on campus at one of the 36 residential halls scattered across the 200+

acres of the main campus. About 75% of the students are Texas residents.

The university uses municipal water and sewage services. There have been no breaks or

work on water or sewage lines in the past year. There has been no recent road work or

digging around campus.

The campus dining service includes two cafeterias managed by the same company and

about half a dozen fast food establishments; about 2,000 students belong to the university

meal plan which is limited to persons living on campus. Most on-campus students dine

at the main cafeteria which serves hot entrees, as well as items from the grill, deli bar,

and a salad bar. A second smaller cafeteria on campus offers menu selections with a per

item cost and is also accessible to meal plan members. In contrast to the main cafeteria,

the smaller cafeteria tends to be used by students who live off campus and university

staff. The smaller cafeteria also offers hot entrees, grilled foods, and a salad bar, but has

no deli bar. 

Spring break is to begin on March 13 at which time all dining services will cease until

March 23. Although many students will leave town during the break, it is anticipated

that about a quarter of those living on campus will remain.

Hypothesis generating interviews were undertaken with seven of the earliest cases reported by

the emergency rooms and the Student Health Center; all of the cases had onset of illness on

March 10. Four were male and three were female; all but one was a freshman. Two students

were psychology majors; one each was majoring in English and animal husbandry. Three

students were undecided about their major. 

The students were from five different residential halls and all reported eating most of their meals

at the university’s main cafeteria. During the past week, all but one student had eaten food from

the deli bar; two had eaten food from the salad bar, and three from the grill. Seven-day food

histories revealed no particular food item that was common to all or most of the students. 

Except for the psychology majors, none of the other students shared any classes; only one

student had a roommate with a similar illness. Five students belonged to a sorority or a
Gastroenteritis at a University in Texas

Student’s version - p. 10

fraternity. Three students had attended an all school mixer on March 6, the Friday before the

outbreak began; two students went to an all night science fiction film festival at one of the

dorms on March 7. Students reported attendance at no other special events; most had been

studying for midterm exams for most of the weekend.

Question 11: Using information available to you at this point, state your leading hypothesis(es)

on the pathogen, mode of transmission, source of the outbreak, and period of interest. 

Question 12: What actions would you take? 
Gastroenteritis at a University in Texas

Student’s version - p. 11

PART IV - ENVIRONMENTAL INVESTIGATION

Based on clinical findings, the descriptive epidemiology of early cases, and hypothesisgenerating interviews, investigators hypothesized that the source of the outbreak was a viral

pathogen spread by a food or beverage served at the main cafeteria at the university between

March 5 and 10. As a result, TDH environmental sanitarians inspected the main cafeteria and

interviewed staff on March 12.

Thirty-one staff members were employed at the cafeteria of whom 24 (77%) were foodhandlers. 

Except for one employee who worked at the deli bar and declined to be interviewed, all dining

service personnel were interviewed.

Question 13: What key areas should be explored during interviews with the cafeteria

foodhandlers? 
Gastroenteritis at a University in Texas

Student’s version - p. 12

Cafeteria staff were questioned about their responsibilities in the cafeteria such as the foods they

handled, which meals they served, and where they usually worked (e.g., deli bar, grill). They

were also asked about use of gloves, handwashing practices, their work schedule during the

week before the outbreak, and if they had been ill at that time. 

In the cafeteria, the deli bar had its own preparation area and refrigerator. During mealtimes,

sandwiches were made to order by a foodhandler. Each day, newly prepared deli meats, cheeses,

and condiments were added to partially depleted deli bar items from the day before (i.e., without

discarding leftover food items). While the deli was open for service, sandwich ingredients were

not kept refrigerated or on ice. The deli bar containers were not routinely cleaned. Samples of

leftover food, water, and ice were collected.

None of the foodhandlers interviewed reported being ill in the last two weeks. Stool cultures

were requested from all cafeteria staff. 

Before dinner on March 12, the City Health Department closed the deli bar.

Question 14: Do you agree with the decision to close the deli bar? What actions would you take

now?
Gastroenteritis at a University in Texas

Student’s version - p. 13

PART V - DESIGNING AN EPIDEMIOLOGIC STUDY TO TEST THE HYPOTHESIS

(STUDY #1)

On the evening of March 12, about 36 hours after the initial call to the health department, TDH

staff conducted a matched case-control study among students at the university. Ill students

(reported from emergency rooms and the Student Health Center) who could be reached at their

dormitory rooms were enrolled as cases. Dormitory roommates who had not become ill were

asked to serve as matched control subjects. Investigators inquired about meals the students

might have eaten during March 5-10 and where the foods were eaten. All information was

collected over the telephone.

Question 15: What are the advantages and disadvantages of undertaking a case-control study

instead of a cohort study at this point in the investigation?

Question 16: How would you define a case for this study? 
Gastroenteritis at a University in Texas

Student’s version - p. 14

Twenty-nine cases and controls were interviewed over the telephone. Investigators tabulated the

most notable results in Table 1. 

Table 1. Risk factors for illness, matched case-control study, main cafeteria, University X, Texas, March

1998.

Exposure

Ill exposed/

Total ill* (%)

Well exposed/

Total well* (%)

Matched

Odds

Ratio**

95%

Confidence

Interval p-value

Ate at deli bar - lunch

on March 9

11/28 (39) 1/29 (3) 11.0 1.6-473 <0.01

Ate at deli bar -

dinner on March 9

7/27 (26) 2/29 (7) 6.0 0.73-275 0.06

Ate at deli bar - lunch

on March 10

8/29 (28) 1/28 (4) 8.0 1.1-354 0.02

Ate at deli bar -

dinner on March 10

2/29 (7) 2/28 (7) 1.0 0.01-79 0.75

Ate at deli bar - lunch

or dinner on March 9

or lunch on March 10

15/27 (56) 3/28 (11) 7.0 1.61-63.5 <0.01

*Denominator does not always total to 29 because several subjects could not remember where they ate the indicated

meal.

**The data pro vided for cases an d contro ls cannot b e used to calculate the m atched od ds ratio whic h is based o n an

analysis of discordant pairs.

Question 17A: How do you interpret these data?
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Student’s version - p. 15

Question 17B: What elements of this case-control study might affect the validity of the

measured association?
Gastroenteritis at a University in Texas

Student’s version - p. 16

Eating at the main cafeteria, in general, was not associated with illness; however eating from the

deli bar during lunch on March 9 or March 10 was significantly associated with illness. Because

such a small number of controls ate at the deli bar, individual food items from the deli bar could

not be examined.
Gastroenteritis at a University in Texas

Student’s version - p. 17

PART VI - DESIGNING AN EPIDEMIOLOGIC STUDY TO REFINE THE

HYPOTHESIS (STUDY #2)

By March 13, one hundred and twenty-five persons with vomiting or diarrhea had been reported

to TDH. TDH invited staff from the Centers for Disease Control and Prevention (CDC) to

participate in the ongoing investigation. CDC staff suggested submission of fresh stool

specimens from ill students for viral studies including reverse transcriptase-polymerase chain

reaction (RT-PCR). TDH and CDC staff decided to undertake an unmatched case-control study

to further explore the source of the outbreak.

Question 18: Who should be enrolled as subjects for this study?
Gastroenteritis at a University in Texas

Student’s version - p. 18

The case-control study was undertaken among students who ate at the main cafeteria. A case

was defined as vomiting or diarrhea ($3 loose bowel movements during a 24-hour period) with

onset on or after March 5, 1998, in a student who was a member of the university meal plan. 

Cases were selected from those reported to TDH by one of the local emergency rooms or the

Student Health Center. Controls were students enrolled in the university meal plan who did not

have nausea, vomiting, or diarrhea since March 5.

Forty cases were randomly selected from the 125 reported through March 13. One hundred and

sixty controls were randomly selected from the university meal plan database.

Question 19: Investigators considered collecting information for the case-control study through

face-to-face interviews, telephone interviews, or self-administered questionnaires. What are the

advantages and disadvantages of each method of data collection? Which method would you

recommend given the circumstances around the outbreak?
Gastroenteritis at a University in Texas

Student’s version - p. 19

The investigators administered the study questionnaire by telephone from March 15-23. 

Students selected for participation were called at their dormitory room or their home telephone

number as recorded in university records. If the student was not present at either location but

information on his/her whereabouts was available, additional phone calls were made to contact

the student. Students not reached during spring break were interviewed on their return to the

university. 

Thirty-six cases and 144 controls were contacted. Cases included in the study were similar to all

cases with respect to gender, age, and year in college. Their dates of onset of illness had a

distribution similar to that seen in Figure 1. 

Results from the unmatched case-control study were tabulated by TDH and CDC

epidemiologists. Only persons who ate at the main cafeteria for the specified period were

included in the meal-specific analyses. (Table 2)

Table 2. Risk factors for illness among persons eating at the main cafeteria, unmatched case-control

study, University X, Texas, March 9-10, 1998.

Exposure Ill exposed/

Total ill 

Well exposed/

Total we ll

Measure of

association p-value

Ate at salad bar -

lunch March 9

9/30 36/100

Ate at salad bar -

dinner March 9

5/18 15/59

Ate at salad bar -

lunch March 10

6/28 23/96

Ate at salad bar -

dinner March 10

6/15 12/44

Ate at salad bar* 13/19 49/69

Ate at deli bar -

 lunch March 9

18/30 12/101

Ate at deli bar -

 dinner March 9

7/18 5/61

Ate at deli bar - 

lunch March 10

13/29 12/96

Ate at deli bar - 

dinner March 10

4/16 4/44
Gastroenteritis at a University in Texas

Student’s version - p. 20

Ate at deli bar* 28/36 20/116

*for lunch or dinner March 9 or lunch March 10

Question 20: Calculate the appropriate measure of association for these exposures. Interpret the

results.
Gastroenteritis at a University in Texas

Student’s version - p. 21

To identify the specific item(s) at the deli bar causing the outbreak, investigators reanalyzed

study data from only cases and controls who ate at the deli bar during March 9-10. (Table 3)

Table 3. Food items eaten by students who ate at deli bar during implicated meals, unmatched casecontrol study, University X, Texas, March 9-10, 1998.*

Exposure

Ill exposed/

Total ill (%)

Well exposed/

Total well (%) Odds Ratio

95% Confidence

Interval p-value

American

cheese

13/28 (46) 4/20 (20) 3.4 0.80-17.5 0.06

Swiss cheese 8/28 (29) 8/20 (40) 0.61 0.15-2.4 0.30

Ham 11/28 (39) 6/20 (30) 1.5 0.38-6.3 0.36

Turkey 15/28 (54) 11/20 (55) 0.95 0.26-3.5 0.57

Shredded lettuce 13/28 (46) 10/20 (50) 0.87 0.24-3.2 0.52

Tomato 7/28 (25) 6/20 (30) 0.78 0.18-3.5 0.50

Pickles 7/28 (25) 7/20 (35) 0.63 0.15-2.6 0.63

Mayonnaise 20/28 (71) 9/20 (45) 3.1 0.78-12.4 0.06

Mustard 10/28 (36) 9/20 (45) 0.68 0.18-2.6 0.52

*includes lunch and dinner on March 9 and lunch on March 10

Question 21: Interpret the results in Table 3.
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Student’s version - p. 22

PART VII - ADDITIONAL INVESTIGATIONS

Water and ice samples obtained from the cafeteria on March 12 were negative for fecal

coliforms. Stool cultures and rectal swabs from the 23 foodhandlers were negative for bacteria. 

The staff member who initially refused to be interviewed worked primarily at the deli bar. 

When she finally agreed to be interviewed on March 23, she reported slicing ham on March 9,

for use at the deli bar during lunch and dinner that day, and lunch the following day. She also

prepared and served sandwiches for these same meals. She reported that she had worn gloves

while slicing the ham and while serving sandwiches at the deli bar. She denied any

gastrointestinal illness during the outbreak period but reported that her infant had been sick with

watery diarrhea since March 7, two days before she prepared items for the implicated meals. 

Because the foodhandler wore gloves during food preparation and serving, she did not feel that

handwashing was an important activity.

Of the 18 fresh stool specimens sent on ill students to CDC, 9 (50%) had evidence of Norwalklike virus (NLV) by RT-PCR. Of the four deli foods available from the implicated meals, only

the ham sample, from March 9, was positive by RT-PCR for the presence of NLV RNA. NLV

was also detected by RT-PCR in a stool sample from the ill infant of the foodhandler who

prepared the deli sandwiches on March 9. The sequence of the amplified product was identical

to those products from the ill students and the deli ham.

Question 22: Do you think the evidence implicates the foodhandler as the source of the

outbreak? Explain.
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Student’s version - p. 23

PART VIII - CONTROL

Spring break at the university ended on March 23. The chief of the campus food service called

TDH to find out what must be done to reopen the deli bar. 

Question 23: Which of the following actions would you recommend? What are the pros and

cons of each?

A) throw away all leftover deli bar foods and ingredients

B) clean and disinfect all equipment and surfaces in the deli bar

C) require all foodhandlers to submit a stool specimen before allowing them to return to

work

D) educate foodhandlers on proper foodhandling procedures including handwashing and

appropriate hot-holding and cold-holding temperatures

E) develop a sick foodhandlers policy
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Student’s version - p. 24

Question 24: Who might you consult in developing actions/policies for the campus food service

to prevent a recurrence of this problem in the future? Why?
Gastroenteritis at a University in Texas

Student’s version - APPENDICES

APPENDIX 1

 STATE DEPARTMENT OF HEALTH

Date: 03/11/97

 #: 97-076

PERSON COMPLETING INFORMATION

Name: Xavier Onassis F : ( 512) 555 - 1234

Affiliation: 9 Local BOH (town): ______________ : State DPH (division): Epi 9

Other:_____________

REPORTER / COMPLAINANT

Name: Refused to provide F : ( ) _______ - ___________

Affiliation: : Consumer specify: 

 9 Laboratory division, ___________________________________________

 9 Local BOH facility,

 9 Medical Provider address, ____________________________________________

 9 State DPH town, etc.

 9 Other ____________________________________________

ILLNESS INFORMATION

# Persons ill: 2 

Symptoms: (% reporting)

: Diarrhea (both) : Vomiting (both) : Nausea (both) 9 Abdominal cramps 

: Fever (only one) 9 Bloody stool : Headache (only one) 9 Muscle aches

9 Chills 9 Loss of appetite : Fatigue (both) 9 Dizziness

9 Burning in mouth 9 Other symptoms: None 

Onset: Earliest Date: 03/10/97 Time: 11:30 9 AM :PM

 Latest (if $ 2 ill) Date: 03/11/97 Time: 2:30 : AM 9 PM

Duration: 9 Less than 24 Hours 9 24-48 Hours 9 More than 48 Hours : Ongoin g 9 Unknown

Ill Persons: Age

 Name Address/Town F (yrs) Occupation Med. Provider/ F

1 : same as reporter University X refused 18 student none

2 refused University X refused 19 student none

3

4

Medic al attention received (by anyone)? 9 Yes : No 9 Unknown Y If Yes, specify above: 

Stool specimens submitted (by anyone)? 9 Yes : No 9 Unknown Y To SLI 1

? 9 Yes 9 No 9

Unknown

Medical diagnosis reported?

Foodborne Illness Complaint Worksheet
Gastroenteritis at a University in Texas

Student’s version - APPENDICES

FOOD HISTORY

Y Obtain history back 72 hours prior to symptoms, or, if organism identified, use min and ma x incubation periods

(see p.3)

Y If $2 ill, follow above time frame for common meals (foods) only 

 # Restaurant / store where

 Date & Time 2

 Exp3

 Food(s) consumed purchased (name, town) Place consumed

 9B

March 8 9 L

 9 D

Univers ity cafeteria 9 Same (as left) 

9 Home

9 Other (specify):

 9 B

March 9 9 L

 9

Univers ity cafeteria 9 Same (as left) 

9 Home

9 Other (specify):

 9 B

March 10 9 L

 :

Anchovy pizz a and beer Local pizzeria 9 Same (as left) 

9 Home

: Other (specify):

 9 B

 9 L

 9

9 Same (as left) 

9 Home

9 Other (specify):

 9 B

 9 L

 9 D

9 Same (as left) 

9 Home

9 Other (specify):

 9 B

 9 L

 9 D

9 Same (as left) 

9 Home

9 Other (specify):

NOTES

Student refused to provide food history beyond foods eaten at local pizzeria. He reported that he and his roommate

shared no other meals in the last 72 hours; they ate separately at the University cafeteria.
Gastroenteritis at a University in Texas

Student’s version - APPENDICES

FOOD TESTING

Food(s) available for testing? 9 Yes 9 No : Unknown Sent to SLI 1? 9 Yes 9 No 9 Unknown

If Yes, specify food(s) & sources:

Product and Manufacturer Information for Commercially-Processed Food(s)

Product name: ____________________________________________ Code/lot #______________________

Expiration date: _____ /_____ /_____ Package size/type: ________________________________________

Manufacturer: __________________________________________________ F: ( ) ______ - __________

Address: 

Incubation Periods for Selected Organisms

 Min Max Min Max Min Max

B. cereus (short) 1 hr 6 hrs E. coli O157:H7 3 days 8 Staph. aureus 30 min 8 hrs

B. cereus (long) 6 hrs 24 hrs Hepatitis A 15 days 50 days Shigella 12 hrs 96 hrs

Campylobacter 1 day 10 days Salmonella (non-typhi) 6 hrs 5 days Vibrio cholerae few hrs 5 days

Cyclospora 1 day 14 days Salmonella typh i 1 wk 3 wks Viral GI 12 hrs 48 hrs

C. perfringens 6 hrs 24 hrs Shellfish poisoning min few hrs Yersinia 3 days 7 days

1 State L abora tory Institute

2 Always record Time if possible; otherwise, choose B=brea kfast, L=lunc h, D=dinner 

3 Total # perso ns (both ill and well) wh o consu med in dicated f ood(s)
Gastroenteritis at a University in Texas

Student’s version - APPENDICES

APPENDIX 2. Causative agents for acute enteric illness

INFECTIOUS

Bacteria

Aeromonas (not proven)

Bacillus cereus

Campylobacter 

Clostridium perfringens

Escherichia coli

 Shiga Toxin producing E. coli (STEC)

 Enterotoxin producing E. coli (ETEC)

 Enteroinvasive E. coli (EIEC)

 Enteropathogenic E. coli (EPEC)

Plesiomonas (not proven)

Salmonella, non-typhoid

Salmonella Typhi

Shigella

Vibrio

Yersinia enterocolitica

Viruses

Norwalk and Norwalk-like agents (caliciviruses) 

Rotavirus

Hepatitis A

Parasites

Cryptosporidium parvum

Cyclospora

Entamoeba histolytica

Giardia lamblia

TOXINS

Bacillus cereus

Staphylococcus aureus

Clostridium perfringens

Clostridium botulinum

heavy metals (cadmium, copper, zinc, tin)

mushroom toxins

fish and shellfish toxins (scombroid,

ciguatera)

insecticides

drugs

boric acid

OTHER

psychogenic

radiation
Gastroenteritis at a University in Texas

Student’s version - APPENDICES

APPENDIX 3. Recommendations for Collection of Stool Specimens for Laboratory

Examination (from the Morbidity and Mortality Weekly Report: Recommendations and Reports

1990;30 [No. RR-14])

Specimen collection is critical in identifying the causative agent in an outbreak of

gastroenteritis. Bacteria, viruses, and parasites each require different specimens and methods of

storage and transport for optimal diagnosis. When the causative agent is unknown, one should

consider plausible pathogens based on predominant signs and symptoms and other outbreak

information. 

For bacterial pathogens

Rectal swabs or swabs of fresh stools should be placed in refrigerated Cary-Blair transport

medium. If the specimens are likely to be examined within 48 hours after collection, they can be

refrigerated at 4°C until shipping. Specimens should be enclosed in a secure container and

placed in a waterproof bag. Specimens should be packed with ice or frozen refrigerant packs in

an insulated box.

If specimens must be held longer than 48 hours, they should be frozen as soon as possible after

collection. Although storage in an ultra-low freezer (-70°C) is preferable, storage in a hometype freezer (if it is properly set at -20°C) is acceptable for short periods. So that the specimens 

remain frozen, they should be shipped on dry ice. Sufficient dry ice should be used to keep

specimens frozen until the laboratory processes them (i.e., enough dry ice to fill one-third to onehalf of the shipping container). Glass tubes should not be in direct contact with the dry ice; a

layer of paper or other material should be placed between the tubes and the dry ice. To prevent

excess exposure to carbon dioxide (from the dry ice), screw caps should be tightened and sealed

with electrical tape or specimens should be sealed in a plastic bag within the container of dry

ice.

For viral pathogens

Collect as large a quantity of diarrheal stool as can be obtained (at least 10 cc). Place in a leakproof, clean, dry container, and refrigerate immediately at 4°C. DO NOT FREEZE

SPECIMENS IF ELECTRON MICROSCOPY EXAMINATION IS ANTICIPATED. The use of

rectal swabs to detect viral causes of gastroenteritis is discouraged because the sensitivity of

detection compared to bulk stool is suspected to be low.

For parasites

Mix fresh bulk stool specimens thoroughly with each of two preservatives, 10% formalin and

polyvinyl alcohol fixative, at a ratio of one part of stool to 3 parts of preservative. If there is any

delay in obtaining the preservatives, refrigerate untreated stool specimens at 4°C for up to 48

hours. For routine microscopy, DO NOT FREEZE. Once preserved, the specimens can be stored

and transported at room temperature or refrigerated. Note, it is now possible to do genotyping

on many parasites, but this may require different preservatives. If parasites are considered a

likely etiology, contact a lab that has the capacity to conduct genetic testing and ask for specific

instructions. Currently recommended preservatives for genetic analysis include freezing the

specimen or preserving it in ethanol or potassium dichromate.