**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.     |
| Griffin^1^                                                            |
|                                                                       |
| ^1^Centers for Disease Control and Prevention, ^2^Virginia Department |
| of Health, ^3^Michigan Department of Community Health**,** ^4^Medical |
| College of Virginia, ^5^Virginia Division of Consolidated Laboratory  |
| Services                                                              |
|                                                                       |
| **Case study and instructor's guide created by:** Jeanette K.         |
| Stehr-Green, MD                                                       |
+-----------------------------------------------------------------------+

> NOTE: This case study is based on two real-life outbreak
> investigations undertaken 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 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]{.underline}. 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**

**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.

[Question 1A:]{.underline} What could account for the increase in cases
reported to MDCH?

[Question 1B]{.underline}: What information might help determine which
of these explanations is the most likely cause of the increased numbers?

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)

![](media/image1.png){width="0.5in" height="3.0in"}

Figure 1. Typical DNA

banding pattern

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.

[Question 2:]{.underline} 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.

![](media/image2.jpeg){width="4.5in" height="4.559722222222222in"}

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.

**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:]{.underline} What are the advantages and disadvantages of
this case definition? How might you change it?

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:]{.underline} 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)

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)

![](media/image3.png){width="5.986111111111111in"
height="3.9444444444444446in"}

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.

[Question 5:]{.underline} 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:]{.underline} 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.)

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:]{.underline} 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.

**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:]{.underline} How would you define controls for this study?

[Question 8B:]{.underline} Do you agree with the investigators' decision
to match on age group and gender? Why or why not?

[Question 9:]{.underline} What methods might be used to identify
controls? What are the advantages and disadvantages of each method?

[Question 10:]{.underline} Over what time period would you examine
exposures to possible risk factors for cases? For controls?

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.

**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:]{.underline} What are possible explanations for the
association between illness and sprouts?

[Question 12:]{.underline} 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?

[Question 13:]{.underline} 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.)

**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 dead-ends. 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:]{.underline} What criteria should be considered before
deciding to undertake a traceback procedure? Would you consider doing a
traceback in the Michigan outbreak?

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

[Question 15:]{.underline} What information on the implicated food item
might facilitate the traceback process?

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.

![](media/image4.png){width="6.0in" height="2.888888888888889in"}

[Question 16:]{.underline} Given the results of the Michigan and
Virginia traceback investigations, where is the most likely point of
contamination in the production of the sprouts?

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:]{.underline} In inspecting the alfalfa fields and
harvesting process, what possible points of contamination should you
consider?

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:]{.underline} What interventions/control measures would you
suggest at this point?

**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:]{.underline} 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.

**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.

**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.

**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. Department of Agriculture
> (USDA), the Food and Drug Administration (FDA), and selected state and
> local health departments. In 1997, FoodNet conducted population‑based
> active surveillance for confirmed cases of *Campylobacter*,
> *Escherichia coli* O157, *Listeria*, *Salmonella*, *Shigella*,
> *Vibrio*, and *Yersinia* infections in Minnesota, Oregon, and selected
> counties in California, Connecticut, and Georgia (total population:
> 16.1 million).

**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]{.underline}

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]{.underline}

No antibiotics in two weeks before illness

No antacids in two weeks before illness

No chronic illness

[EXPOSURES IN 7 DAYS BEFORE ILLNESS:]{.underline}

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:]{.underline}

High risk foods:

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

[6/15 (Sunday)]{.underline}

Breakfast: coffee with cream

Lunch: yogurt, diet coke

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

[6/16 (Monday)]{.underline}

Breakfast: coffee with cream

Lunch: yogurt, diet coke

Dinner: oriental vegetables with beef, rice, iced tea

[6/17 (Tuesday)]{.underline}

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)]{.underline}

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)]{.underline}

Breakfast: coffee with cream

Lunch: bean burrito, diet coke

Dinner: pasta with shrimp and snow peas, iced tea

[6/20 (Friday)]{.underline}

Breakfast: coffee with cream

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

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

Party: variety of cheese and crackers, white wine

[6/21 (Saturday)]{.underline}

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:]{.underline}

5^th^ Street Diner City: 35

[USUAL STORES OR MARKETS:]{.underline} (does own shopping)

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

[STORES OR MARKETS FOR PRODUCE:]{.underline}

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

[OTHER SPECIAL EVENTS:]{.underline} party at friends on 6/20

[OTHER ILL PERSONS:]{.underline} no family members or acquaintances ill

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]{.underline}

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]{.underline}

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:]{.underline}

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:]{.underline}

High risk foods:

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

[6/18 (Wednesday)]{.underline}

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)]{.underline}

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

[6/20 (Friday)]{.underline}

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)]{.underline}

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)]{.underline}

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)]{.underline}

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)]{.underline}

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:]{.underline} did not eat out

[USUAL STORES OR MARKETS:]{.underline} (wife does all of the shopping)

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

[STORES OR MARKETS FOR PRODUCE:]{.underline}

Store: 5 (City: 49)

[OTHER SPECIAL EVENTS:]{.underline} square dancing at senior citizens
center (no food served)

[OTHER ILL PERSONS]{.underline}: wife and mother-in-law not feeling
well, loose stools and abdominal cramps

**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.

Photograph 1. Alfalfa sprouts 5 days after germination.

![](media/image5.jpeg){width="3.1902777777777778in" height="3.39375in"}

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.