A Multistate Outbreak of E. coli O157:H7 Infection

STUDENT’S VERSION

Original investigators: Thomas Breuer,1

 Denise H. Benkel,1,2 Roger L. Shapiro,1

 William N.

Hall,3

 Mary M. Winnett,4

 Mary Jean Linn,2

 Jakob Neimann,1

 Timothy Barrett,1

 Stephen

Dietrich,3 Francis P. Downes,

3

 Denise M. Toney,5 James L. Pearson,5 Henry Rolka,1 Laurence

Slutsker,1 and Patricia M. Griffin1

1Centers for Disease Control and Prevention, 2Virginia Department of Health, 3Michigan

Department of Community Health,

4Medical College of Virginia, 5Virginia Division of

Consolidated Laboratory Services

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

NOTE: This c ase study is based o n two re al-life outb reak inve stigation s underta ken in

Michigan and Virginia in 1997. Some aspects of the original outbreaks and

investigations have been altered, however, to assist in meeting the desired teaching

objective s and allow completion o f the case stu dy in less th an 3 ho urs. 

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

appro ach to fo odbor ne disea se outbre ak investig ation. Pr ocedur es and p olicies in

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

outbreak to outbreak.

It is anticipa ted that the epidem iologist inv estigating a foodb orne dise ase outb reak will

work within the framewo rk of an “investiga tion 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, th at outbre ak investig ations are successfully com pleted. 

Please send us your comments on this case study by visiting our website at

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

your commen ts.

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

A Multistate Outbreak of E. coli O157:H7 Infection

Learning objectives:

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

1. describe the unique role the laboratory can play in the detection and investigation of a

foodborne disease outbreak

2. perform in-depth interviews of selected case-patients to generate hypotheses about the

source of an outbreak and mode of transmission

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

the case definition and appropriate comparison group)

4. list three ways to select a comparison group for a study and the advantages and

disadvantages of each method

5. list detailed product information that will facilitate a traceback procedure 

6. discuss the relative merits of an intervention based on changes in product processing

(or design) versus changes in consumer or producer behaviors

PART I - OUTBREAK DETECTION

Escherichia coli O157:H7 was first identified as a human pathogen in 1982 in the United States

of America, following an outbreak of bloody diarrhea associated with contaminated hamburger

meat. Sporadic infections and outbreaks have since been reported from many parts of the world,

including North America, Western Europe, Australia, Asia, and Africa. Although other animals

are capable of carrying and transmitting the infection, cattle are the primary reservoir for E. coli

O157:H7. Implicated foods are typically those derived from cattle (e.g., beef, hamburger, raw

milk); however, the infection has also been transmitted through contact with infected persons,

contaminated water, and other contaminated food products. 

Infection with E. coli O157:H7 is diagnosed by detecting the bacterium in the stool. Most

laboratories that culture stool do not routinely test for E. coli O157:H7, but require a special

request from the health care provider. Only recently has E. coli O157:H7 infection become

nationally notifiable in the U.S. Outside the U.S., reporting is limited to a few but increasing

number of countries. 

In the last week of June 1997, the Michigan Department of Community Health (MDCH) noticed

an increase in laboratory reports of E. coli O157:H7 infection. Fifty-two infections had been

reported that month, compared with 18 in June of 1996. In preliminary investigations, no

obvious epidemiologic linkages between the patients were found. The increase in cases

continued into July.
A Multistate Outbreak of E. coli O157:H7 Infection

Studen t’s version - p. 2

Question 1A: What could account for the increase in cases reported to MDCH? 

Question 1B: What information might help determine which of these explanations is the most

likely cause of the increased numbers?
A Multistate Outbreak of E. coli O157:H7 Infection

Studen t’s version - p. 3

Laboratory subtyping can help determine if an increased number of isolates of the same bacterial

species results from a common source outbreak. Subtyping methods are based on selected

biologic and/or genetic characteristics of bacteria that tend to differ between isolates of the same

species. In a common source outbreak, however, isolates typically arise from the same parent

organism. These isolates will be similar to each other with respect to these biologic and genetic

characteristics and have similar subtyping results. 

One subtyping method is DNA

"fingerprinting" by Pulsed Field Gel

Electrophoresis (PFGE). In DNA

fingerprinting, the bacterial DNA is cut into

pieces. The pieces are separated by placing

them in a jelly-like substance (i.e., the gel),

acting as a sieve, to which a pulsing electric

field is applied. The electric field drives the

DNA pieces across the gel over a period of

hours. The smaller pieces move through the

gel more quickly and the larger pieces more

slowly resulting in a separation of the DNA

into distinct bands. The bands are made to

fluoresce and are read under ultraviolet

illumination. This DNA “fingerprint”

resembles a bar code. (Figure 1) 

 

 

 

Figure 1. Typical DNA

banding p attern

resulting from PFGE.

Different DNA composition will result in different PFGE banding patterns. Bacteria descended

from the same original parent will have virtually identical DNA and their DNA fingerprints will

be indistinguishable. Identification of a cluster of isolates with the same PFGE pattern suggests

that they arose from the same parent and could be from the same source. 

Similar DNA fingerprints alone, however, are insufficient to establish a linkage between isolates

and a common source outbreak. An epidemiologic investigation is necessary to demonstrate that

there is a common source and to identify it. To be most useful, PFGE subtyping needs to be

performed on a routine basis, in real time, so that results are available (and reviewed) soon after a

case is first detected.
A Multistate Outbreak of E. coli O157:H7 Infection

Studen t’s version - p. 4

Question 2: Compare the DNA fingerprints in Figure 2 from seven of the Michigan E. coli

O157:H7 cases. Each isolate has its own vertical lane (i.e., column). Controls appear in lanes

#1, 5, and 10. Which Michigan isolates appear similar?

Figure 2. PFGE results on E. coli O157:H7 isolates from Michigan, June-July 1997.
A Multistate Outbreak of E. coli O157:H7 Infection

Studen t’s version - p. 5

DNA fingerprinting, performed in the MDCH State Laboratory during the second week of July

showed that 17 of the first 19 E. coli O157:H7 isolates from June-July were indistinguishable. 

They did not match any fingerprints from a convenience sample of isolates from patients with E.

coli O157:H7 infection before May.

Based on the PFGE findings, MDCH suspected the cases of E. coli O157:H7 infection resulted

from a common source. On July 15, MDCH initiated an investigation. The Centers for Disease

Control and Prevention (CDC) was asked to join the investigation.
A Multistate Outbreak of E. coli O157:H7 Infection

Studen t’s version - p. 6

PART II - DESCRIPTIVE EPIDEMIOLOGY AND HYPOTHESIS GENERATION

The incubation period for E. coli O157:H7 ranges from 3-8 days with a median of 3-4 days. The

infection often causes severe bloody diarrhea and abdominal cramps, but can also cause a

nonbloody diarrhea or result in no symptoms. In some persons, particularly children under 5

years of age and the elderly, the infection can cause a complication called hemolytic uremic

syndrome, in which the red blood cells are destroyed and the kidneys fail. About 2-7% of

infections lead to this complication.

For the outbreak investigation in Michigan, a case was defined as diarrhea ($3 loose bowel

movements a day) and/or abdominal cramps in a resident of Michigan with onset of symptoms

between June 15 and July 15 and a stool culture yielding E. coli O157:H7 with the outbreak

strain PFGE pattern.

Question 3: What are the advantages and disadvantages of this case definition? How might you

change it?
A Multistate Outbreak of E. coli O157:H7 Infection

Studen t’s version - p. 7

Of the initial 38 persons who met the case definition, 26 (68%) were female with a median age of

31 years. (Table 1)

Table 1. Age group and gender distribution for persons with E. coli O157:H7 infection and the outbreak

PFGE pattern, Michigan, June 15 - July 15, 1997. (N=38)

Age group

(years)

Gender

TOTAL

Male Female

0-9 2 (17%)* 2 (8%) 4 (11%)

10-19 2 (17%) 3 (12%) 5 (13%)

20-39 3 (25%) 9 (35%) 12 (32%)

40-59 2 (17%) 8 (31%) 10 (26%)

60+ 3 (25%) 4 (15%) 7 (18%)

TOTAL 12 (101%) 26 (101%) 38 (100%)

 * percentages refer to column totals.

Question 4: Compare the age and gender distribution of E. coli O157:H7 cases from the

Michigan outbreak and those reported from U.S. FoodNet sites in 1997. (see Appendix 1)
A Multistate Outbreak of E. coli O157:H7 Infection

Studen t’s version - p. 8

The 38 cases of E. coli O157:H7 infection meeting the investigation case definition were

reported from 10 counties in the lower peninsula of Michigan. Onset of illness occurred from

mid-June to mid-July, peaking on June 22. (Figure 3) 

Figure 3. Date of illness onset for persons with E. coli O157:H7 infection and the outbreak PFGE

pattern, Michigan, June 15 - July 15, 1997. (N=38)

From July 16 - 19, hypothesis-generating interviews were undertaken with seven patients. These

patients lived in four different counties and ranged in age from 5-69 years. Three of the patients

were female.
A Multistate Outbreak of E. coli O157:H7 Infection

Studen t’s version - p. 9

Question 5: What kinds of questions would you ask in the hypothesis-generating interviews? Be

sure to consider all possible modes of transmission of E. coli O157:H7. 

Question 6: Working in groups of 2-4 students, role play a hypothesis-generating interview of

one of the case-patients. One student should play the patient and will be given information about

that patient (see Appendix 2 “Patient #1" and “Patient #2"). Another student should play the

investigator and will interview the patient. Efforts should be made to simulate a real interview

based on the information provided. After 15 minutes, you will be asked to share your experience

in interviewing the patient. (If time permits, students can switch roles and a second “patient” can

be interviewed using material in Appendix 2.)
A Multistate Outbreak of E. coli O157:H7 Infection

Student’s version - p. 10

Hypothesis-generating interviews revealed that most cases had consumed lettuce and alfalfa

sprouts in the week before they became ill. No single restaurant or social event was identified in

common.

Question 7: Given your knowledge about E. coli O157:H7, the descriptive epidemiology of the

initial cases, and the results of hypothesis-generating interviews, outline the information available

at this point on the source of the outbreak and mode of transmission and state your leading

hypothesis.
A Multistate Outbreak of E. coli O157:H7 Infection

Student’s version - p. 11

PART III - DESIGNING AN EPIDEMIOLOGIC STUDY TO TEST THE HYPOTHESIS

To test the hypothesis on the source of the outbreak, MDCH and CDC conducted a case-control

study from July 21-27. Thirty-one of the initial 38 persons meeting the original case definition

(i.e., those not used in hypothesis generating interviews) were included as cases. It was decided

that two controls would be selected for every case and would be matched to the case by age

group (0-<2 years, 2-<5 years, 5-<12 years, 12-<18 years, 18-<60 years, and 60+ years) and

gender. 

Question 8A: How would you define controls for this study? 

Question 8B: Do you agree with the investigators’ decision to match on age group and gender? 

Why or why not?
A Multistate Outbreak of E. coli O157:H7 Infection

Student’s version - p. 12

Question 9: What methods might be used to identify controls? What are the advantages and

disadvantages of each method?

Question 10: Over what time period would you examine exposures to possible risk factors for

cases? For controls?
A Multistate Outbreak of E. coli O157:H7 Infection

Student’s version - p. 13

The investigators identified controls for the study using sequential digit dialing. Exposure

information among cases was collected for the 7 days before onset of illness. For controls,

exposure information was collected for the 7 days before the interview and for the 7 days before

the onset of illness in the matching case.

Twenty-seven case-control sets were interviewed; the remaining case-patients could not be

reached. 
A Multistate Outbreak of E. coli O157:H7 Infection

Student’s version - p. 14

PART IV - ANALYSIS AND INTERPRETATION OF EPIDEMIOLOGIC RESULTS

In the case-control study, 15 (56%) of 27 ill persons reported eating alfalfa sprouts in the 7 days

before onset of illness, but only three (6%) of 53 controls reported eating them in the 7 days

before the interview (matched odds ratio [MOR]: 27, 95% confidence interval 5-558.) When

controls were asked about alfalfa sprout consumption for the same 7-day interval as ill persons, a

similar association was observed; four of 53 controls reported eating sprouts (MOR 25, 95% CI

4-528.) No other food item was significantly associated with illness.

Question 11: What are possible explanations for the association between illness and sprouts?

Question 12: How might you explain the 12 ill persons in the study who did not report eating

alfalfa sprouts in the 7 days before they became ill?
A Multistate Outbreak of E. coli O157:H7 Infection

Student’s version - p. 15

Question 13: What control measures might you consider at this point? What further studies

might you suggest? (See Appendix 3 for a description of alfalfa sprouts and the typical sprouting

procedure.)
A Multistate Outbreak of E. coli O157:H7 Infection

Student’s version - p. 16

PART V - OTHER INVESTIGATIONS

Tracebacks of food are often necessary to identify sources of contamination and quickly limit a

public health threat by removing these sources. One purpose of a traceback is to ascertain the

distribution and production chain for a food product so that an effective recall can be undertaken. 

Tracebacks can also clarify the point or points at which the implicated food was likely to have

become contaminated and help determine how to prevent similar outbreaks in the future. 

Epidemiologic tracebacks can accomplish each of these goals, but are different from the more

detailed, regulatory tracebacks which follow rules of legal evidence.

An epidemiologic traceback usually begins with the information available at the time of purchase

of the implicated food item and extends back to the very beginning of its production. All

production steps, from harvest to consumption, are examined. 

Full tracebacks leading to formal product recalls can be time-consuming and result in many deadends. Pertinent information and records are often missing or poorly maintained. Traceback

efforts may require hundreds of hours of tedious work and may extend to other states and

countries.

Question 14: What criteria should be considered before deciding to undertake a traceback

procedure? Would you consider doing a traceback in the Michigan outbreak? 
A Multistate Outbreak of E. coli O157:H7 Infection

Student’s version - p. 17

MDCH and CDC decided to do an epidemiologic traceback of the alfalfa sprouts implicated in

the Michigan outbreak.

Question 15: What information on the implicated food item might facilitate the traceback

process?
A Multistate Outbreak of E. coli O157:H7 Infection

Student’s version - p. 18

Of the 16 patients who ate sprouts for whom the source of the sprouts could be traced, 15 led to a

single sprouting facility, facility A in Michigan; in the remaining traceback, the patient could

have eaten sprouts from either facility A or facility B in Michigan. (Figure 4) Facility A and B

were the only facilities that sprouted alfalfa seed in the state. Sprouts grown by facility A at the

time of the outbreak came from two lots of seed: one from Idaho and one from Australia.

At this point, the investigators became aware of a concurrent outbreak of E. coli O157:H7

infection in Virginia. CDC subtyped the strains from Virginia and identified the same PFGE

pattern as in the Michigan outbreak. A case-control study conducted by the Virginia Department

of Health (VDH) linked the concurrent outbreak of O157:H7 infections to alfalfa sprouts. 

In Virginia, the source of sprouts could be traced for 13 patients; all led to one sprouting

company in Virginia. (Figure 4) The Virginia sprouting company was using a single lot of seed

harvested in Idaho -- the same lot as the one used at facility A in Michigan. Traceback of the

seed to the distributor identified it as part of a 17,000 pound lot of which 6,000 pounds still

remained.

Figure 4. Traceback results of the E. coli O157:H7 investigation of alfalfa sprouts in Michigan (MI) and

Virginia (VA), 1997.
A Multistate Outbreak of E. coli O157:H7 Infection

Student’s version - p. 19

Question 16: Given the results of the Michigan and Virginia traceback investigations, where is

the most likely point of contamination in the production of the sprouts?
A Multistate Outbreak of E. coli O157:H7 Infection

Student’s version - p. 20

The implicated seed lot was a blend of 5 lots from fields of four farmers and was harvested

between 1984 and 1996. The seed processor and the farmers were located in Idaho. 

Question 17: In inspecting the alfalfa fields and harvesting process, what possible points of

contamination should you consider?
A Multistate Outbreak of E. coli O157:H7 Infection

Student’s version - p. 21

Inspection of the alfalfa fields revealed three possible sources of contamination: cattle manure,

irrigation water, and deer feces. Although manure is not normally applied to alfalfa fields in

Idaho, cattle feed lots were common in this area and the alfalfa fields of one farmer were adjacent

to a feed lot. Manure may have leaked or been illegally dumped onto the alfalfa fields or run-off

water from neighboring fields, contaminated by manure, may have been used to irrigate the

alfalfa fields. In addition, three of four farmers occasionally saw deer in their fields and one field

was situated next to a wildlife refuge.

The seed from each of the farmers was harvested and mechanically cleaned at the same seed

processing plant. The seeds were then placed in 50 lb. bags. No further processing occurred. 

Most of the seed was produced to plant alfalfa fields (e.g., to produce hay for livestock feed); the

relatively small amount of seed used for sprouting was not handled any differently than the raw

agricultural commodity seed. 

Question 18: What interventions/control measures would you suggest at this point?
A Multistate Outbreak of E. coli O157:H7 Infection

Student’s version - p. 22

PART VI - CONTROL

The implicated seed lot was not distributed to any other sprouting companies in or outside the

United States. The remaining 6,000 lbs. of seed was immediately removed from the marketplace. 

A sample of 500 grams of seed was cultured directly, and the same amount was sprouted and

then cultured; neither yielded E. coli O157:H7.

The Idaho Division of Food and Drugs held meetings at which public health officials explained

to seed growers the need to protect alfalfa and other seeds used in sprouting from contamination

during growing, harvesting, and packing. Both MDCH and the VDH made public television and

radio announcements about the risk of contaminated sprouting seeds and recommended that

persons at high risk for complications from E. coli O157:H7 infection not eat sprouts.

The Center for Food Safety and Quality Enhancement began working with the sprout industry to

identify ways to make sprouts safer for human consumption. In tests with artificially inoculated

seed, treating the seed by soaking it in a chlorine solution* (2000 ppm hypochlorite in 57-60°C

water) at the time of sprouting reduced the level of contamination by a thousand-fold. Irradiation

has also been tested and appears to work well in decontaminating sprout seeds. However, this

treatment leads to diminished sprouting ability and has not been approved by the FDA. 

Question 19: What type of intervention is likely to be most effective against the problem of

sprout contamination: education of producers, education of consumers, or changes in methods of

product processing? Why?

*Chemical treatment with a hypochlorite solution is a U.S. Food and Drug Administration (FDA) approved

treatment of foods.
A Multistate Outbreak of E. coli O157:H7 Infection

Student’s version - p. 23

EPILOGUE

In Michigan, demographic characteristics differed among cases reporting consumption of alfalfa

sprouts and those who did not. The median age of non-sprout eaters was 12 years compared with

38 years for sprout eaters. Onset of illness among non-sprout eaters occurred between June 30

and July 13, with most sprout-related cases occurring in June. 

On interview, it was revealed that seven of the non-sprout eating cases, all children, had swum in

the same man-made lake during the July Fourth holiday weekend or the weekend before. 

Because E. coli O157:H7 can survive for weeks in lake water and has a very low infectious dose,

the outbreak investigators hypothesized that the lake was contaminated by feces from a patient

with illness from sprouts. Children could have acquired illness by swallowing water while

swimming or some other exposure that occurred among persons swimming at the lake (e.g.,

concessions, person-to-person). Testing of the lake water on June 24 and July 7 did not reveal

elevated levels of E. coli.

This outbreak illustrates several important concepts in the investigation of foodborne diseases:

1) The finding of a second mode of transmission among patients with the same DNA

fingerprint emphasizes that new subtyping methods such as PFGE are tools to improve

investigations but cannot substitute for a thorough epidemiologic workup. 

2) Secondary spread of the outbreak strain of E. coli O157:H7 through recreational waters

(or some associated activity) illustrates how a foodborne disease outbreak can extend into

the community and affect those who do not consume the contaminated food.

3) The discovery of a new vehicle for the transmission of E. coli O157:H7 demonstrates

how changes in the food industry have made the control of foodborne diseases more

complex and challenging. New food products are not always accompanied by practices to

ensure their safety. 

4) The multistate nature of this outbreak, indicative of the wide distribution of food products

in today’s market, shows how foodborne disease outbreaks can affect persons

simultaneously in widely separated locations. This means not only foodhandling

practices but disease and outbreak investigation efforts in one part of the world can

readily affect persons in another part.

5) And, finally, the lengthy genesis and conclusion to this outbreak (i.e., cases were first

recognized in June, 1997 and continued to occur as late as September, 1997) suggest the

need for improved investigation of foodborne diseases. Among other things, more

reliable case reporting, routine performance of PFGE on E. coli O157:H7 isolates, and the

examination and comparison of results in real-time will increase the rate of response to

foodborne diseases and decrease the number of people affected by them.
A Multistate Outbreak of E. coli O157:H7 Infection

Student’s version - p. 24

REFERENCES

1. Breuer T, Benkel DH, Shapiro RL, et al. A multistate outbreak of diarrhea and hemolytic

uremic syndrome from Escherichia coli O157:H7 infections linked to consumption of

alfalfa sprouts grown from contaminated seeds. Submitted to Journal of the American

Medical Association (1999).

2. Mahon BE, Pönkä A, Hall WN, et al. An international outbreak of Salmonella infections

caused by alfalfa sprouts grown from contaminated seeds. J Infect Dis 1997;175:876-82.

3. Van Beneden CA, Keene WE, Strang RA, et al. Multinational outbreak of Salmonella

enterica Serotype Newport infections due to contaminated alfalfa sprouts. J Am Med

Assoc 1999:281:158-162.

4. Michino H, Araki K, Minami S, et al. Massive outbreak of Escherichia coli O157:H7

infection in school children in Sakai City, Japan, associated with consumption of white

radish sprouts. Am J Epidemiol 1999;150:787-96.

5. Taormina PJ, Beuchat LR, Slutsker L. Infections associated with eating seed sprouts: an

international concern. Emerg Infect Dis 1999;5:626-34. 
A Multistate Outbreak of E. coli O157:H7 Infection

Student’s version - APPENDICES

APPENDIX 1. Distribution of E. coli O 157:H7 cases reported to FoodNet Sites* by age group

and gender, United States, 1997. (N=340)

Age group

(years)

Gender

TOTAL

Male Female

0-<1 5 (3%) 5 (3%) 10 (3%)

1-9 77 (48%) 77 (43%) 154 (45%)

10-19 36 (22%) 18 (10%) 54 (16%)

20-29 10 (6%) 20 (11%) 30 (9%)

30-39 6 (4%) 12 (7%) 18 (5%)

40-49 7 (4%) 5 (3%) 12 (4%)

50-59 7 (4%) 17 (10%) 24 (7%)

60+ 14 (9%) 24 (13%) 38 (11%)

TOTAL 162 (100%) 178 (100%) 340 (100%)

*Foodborne Diseases Active Surveillance Network (FoodNet) is a collaborative project between

CDC, the U.S. Departmen t of Agriculture (USDA), the Food and D rug Administration (FDA),

and selected state and local health departments. In 1997, FoodNet conducted population-based

active su rveillanc e for confirm ed cases of Campylobacter, Escherichia coli O157 , Listeria,

Salmone lla, Shigella, Vibrio, and Yersinia infections in Minnesota, Oregon, and selected counties

in Califor nia, Con necticut, a nd Geo rgia (total po pulation : 16.1 million). 
A Multistate Outbreak of E. coli O157:H7 Infection

Student’s version - APPENDICES

APPENDIX 2. Background information for role-playing interviews of patients (see Question 6)

PATIENT #1: Helen Dresher

Age: 25 years Sex: Female

Address: City: 35 County: 12

Phone number: (248) 555-0991 (home) (248) 555-1423 (work)

works as office manager for local legal firm, lives in apartment by herself

ILLNESS

Onset of symptoms: 6/22/97

Symptoms: bloody diarrhea, abdominal cramps, vomiting, (no fever)

Duration of symptoms: 5 days

Initially treated with Pepto-Bismal and Imodium AD

Visited Dr. Locke on 6/25/97

Treatment received: ciprofloxacin

PAST MEDICAL HISTORY

No antibiotics in two weeks before illness

No antacids in two weeks before illness

No chronic illness

EXPOSURES IN 7 DAYS BEFORE ILLNESS:

No travel outside Michigan

No swimming or wading in recreation areas

Did not drink water from a private well

No contact with animals

FOOD HISTORY FOR 7 DAYS BEFORE BECOMING ILL:

High risk foods:

Hamburgers: NEG Ground beef: NEG Raw or unpasteurized milk: NEG

6/15 (Sunday)

Breakfast: coffee with cream

Lunch: yogurt, diet coke

Dinner: baked chicken, potatoes, salad with lettuce, cucumbers, carrots, green peppers

6/16 (Monday)

Breakfast: coffee with cream

Lunch: yogurt, diet coke

Dinner: oriental vegetables with beef, rice, iced tea
A Multistate Outbreak of E. coli O157:H7 Infection

Student’s version - APPENDICES

6/17 (Tuesday)

Breakfast: coffee with cream

Lunch: left-over baked chicken, pita bread, sprouts (alfalfa), cucumbers, diet coke

Dinner: noodles in cream sauce, green beans, iced tea

6/18 (Wednesday)

Breakfast: English muffin, coffee with cream

Lunch: yogurt, diet coke

Dinner: salad (lettuce, cherry tomatoes, celery, cheese chunks), crackers, diet ranch salad

dressing 

6/19 (Thursday)

Breakfast: coffee with cream

Lunch: bean burrito, diet coke

Dinner: pasta with shrimp and snow peas, iced tea

6/20 (Friday)

Breakfast: coffee with cream

Lunch: chicken salad sandwich, tomato, sprouts (alfalfa), pickle spear, diet coke (5th Street Diner)

Dinner: broiled fish, rice, salad (lettuce, spinach, carrots), vinaigrette dressing

Party: variety of cheese and crackers, white wine

6/21 (Saturday)

Breakfast: coffee with cream

Lunch: bagel, cream cheese, potato chips, oreos, ding dongs, dove bar, potato chips, M&Ms, diet

coke

Dinner: skip

NAMES AND LOCATIONS OF RESTAURANTS OR CAFETERIA’S WHERE ATE IN THE

7 DAYS BEFORE ILLNESS:

5

th Street Diner City: 35

USUAL STORES OR MARKETS: (does own shopping)

Store: 1 (City: 35) Store: 2 (City: 35) Store: 3 (City: 35)

STORES OR MARKETS FOR PRODUCE:

Store: 1 (City: 35) Store: 2 (City: 35)

OTHER SPECIAL EVENTS: party at friends on 6/20

OTHER ILL PERSONS: no family members or acquaintances ill
A Multistate Outbreak of E. coli O157:H7 Infection

Student’s version - APPENDICES

PATIENT #2: G. Warren Wilson

Age: 69 years Sex: Male

Address: City: 5 County: 5

Phone number: (616) 555-1547 (home)

lives with wife and elderly mother-in-law, retired tire salesman, wife prepares all the food

ILLNESS

Onset of symptoms: 6/25/97

Symptoms: bloody diarrhea, abdominal cramps, (no vomiting or fever)

Duration of symptoms: 7 days

No antidiarrheal medications

Visited Dr. Smith on 6/29/97 (concerned about perforated diverticulum), hospitalized for 4 days

Treatment received: antibiotics, intravenous fluids, transfusion 

PAST MEDICAL HISTORY

No antibiotics in two weeks before illness

No antacids in two weeks before illness

Diverticulitis, gastric ulcer disease, smokes

EXPOSURES IN 7 DAYS BEFORE ILLNESS:

No travel outside Michigan

No swimming or wading in recreation areas

Drinks water from private well (source of water for home)

No contact with animals (wife has 7 cats which do not come into house)

FOOD HISTORY FOR 7 DAYS BEFORE BECOMING ILL:

High risk foods:

Hamburgers: NEG Ground beef: NEG Raw or unpasteurized milk: NEG

6/18 (Wednesday)

Breakfast: fried eggs, bacon, toast, coffee (Sanka), preserves

Lunch: vegetable soup, bread, oatmeal cookies, coffee (Sanka)

Dinner: baked ham, scalloped potatoes, green beans, spinach salad, rolls, butter, ice cream

6/19 (Thursday)

Breakfast: fried eggs, bacon, toast, coffee (Sanka), preserves

Lunch: ham sandwich with Swiss cheese and mustard, corn chips, oatmeal cookies, coffee

(Sanka) 

Dinner: fried chicken, mashed potatoes, lettuce and tomato salad, corn-on-the cob, canned

peaches, rolls, butter, ice cream
A Multistate Outbreak of E. coli O157:H7 Infection

Student’s version - APPENDICES

6/20 (Friday)

Breakfast: fried eggs, bacon, toast, coffee (Sanka), preserves

Lunch: tuna salad sandwich with mayonnaise, sprouts (alfalfa), tomato, pickle, potato chips,

oatmeal cookies, coffee (Sanka)

Dinner: broiled steak, French fries, salad (lettuce, tomato, carrots, celery, red cabbage,

mushrooms), thousand islands salad dressing, bread, butter, ice cream

6/21 (Saturday)

Breakfast: fried eggs, bacon, toast, hash brown potatoes, coffee (Sanka), preserves

Lunch: ham sandwich, coleslaw, chocolate chip cookies, coffee (Sanka)

Dinner: pan fried pork chops, mashed potatoes, green beans, rolls, butter, ice cream

6/22 (Sunday)

Breakfast: waffles, syrup, sausage, coffee (Sanka)

Dinner: pot roast with roasted potatoes and vegetables, apple sauce, bread, butter, peach pie, ice

cream

6/23 (Monday)

Breakfast: fried eggs, bacon, toast, coffee (Sanka), preserves

Lunch: roast beef sandwich with mayonnaise and sprouts (alfalfa), corn chips, peanut butter

cookies, coffee (Sanka)

Dinner: round steak, parsley potatoes, zucchini, bread, butter, ice cream

6/24 (Tuesday)

Breakfast: fried eggs, bacon, toast, coffee (Sanka), preserves

Lunch: roast beef sandwich with Swiss cheese and horse radish, coleslaw, chocolate chip

cookies, coffee (Sanka)

Dinner: chicken and rice casserole, green beans, fruit cocktail, bread, butter, ice cream

NAMES AND LOCATIONS OF RESTAURANTS OR CAFETERIA’S WHERE ATE IN THE

7 DAYS BEFORE ILLNESS: did not eat out

USUAL STORES OR MARKETS: (wife does all of the shopping)

Store: 5 (City: 49) Store: 24 (City: 49) Store: 2 (City: 49)

STORES OR MARKETS FOR PRODUCE:

Store: 5 (City: 49)

OTHER SPECIAL EVENTS: square dancing at senior citizens center (no food served)

OTHER ILL PERSONS: wife and mother-in-law not feeling well, loose stools and abdominal

cramps
A Multistate Outbreak of E. coli O157:H7 Infection

Student’s version - APPENDICES

APPENDIX 3. Alfalfa sprouts

Alfalfa sprouts are produced for human consumption through the germination of alfalfa seeds in

a moist, non-soil environment. Like sprouts from many other seeds, alfalfa sprouts are not

cooked and are consumed within a few days of sprouting. Alfalfa sprouts are more delicate than

other seed sprouts and are used in salads and as a garnish, often to add texture and moisture.

Photog raph 1. A lfalfa spro uts 5 days after germin ation. 

The following method (or a facsimile) is used to sprout alfalfa seeds both commercially and by

private individuals:

1) The seeds are rinsed in water. (Many producers use a solution of water and household

chlorine.)

2) The seeds are covered with water and allowed to soak over night (for about 12 hours).

3) The water is drained and the seeds are placed in sprouting trays (or a jar) where they

continue to drain. 

4) The seeds are rinsed (or misted) with water twice daily until they sprout and reach the

desired length (approximately 2-5 days).

5) After reaching the desired length, the sprouts are removed and rinsed. 

6) Excess moisture is removed.

7) The sprouts are placed in a container, covered, and stored in the refrigerator.