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?

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?

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?

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. The median age of patients was 19 years (range: 18-22 years), 69%

were freshman, and 62% were female. 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

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?