**Botulism in Argentina**

INSTRUCTOR'S VERSION

+-----------------------------------------------------------------------+
| **Original investigators:** Rodrigo G. Villar, MD,^1^ Roger L.        |
| Shapiro, MD,^1^ Silvina Busto, MD, MPH,^2^ Clara Rive-Posse, MD,      |
| MPH,^3^ Guadalupe Verdejo MD, MPH,^4^ Maria Isabel Farace, DVM,^5^    |
| Francisco Rosetti, MS,^5^ Jorge A. San Juan, MD,^6^ Carlos Maria      |
| Julia, MD,MPH,^3^ John Becher, RPh,^1^ Susan E. Maslanka, PhD,^1^     |
| David Swerdlow, MD^1^                                                 |
|                                                                       |
| ^1^Centers for Disease Control and Prevention, ^2^Ministero de        |
| Salud-Region V, ^3^Ministero de Salud y Accion Social, ^4^Pan         |
| American Health Organization, ^5^Departamento de Bacteriologia,       |
| Instituto Nacional de Enfermedades Infecciosas, ^6^Hospital F. J.     |
| Muñiz, Buenos Aires, Argentina                                        |
|                                                                       |
| **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 Buenos Aires, Argentina, 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]{.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**

**Target audience:** epidemiologists and other persons with knowledge of
basic epidemiologic concepts and experience in data collection and
analysis who are interested in learning specific skills for
investigating infectious disease outbreaks

**Trainee prerequisites**: working knowledge of descriptive
epidemiology, epidemic curves, measures of association, stratified
analysis, study design, outbreak investigation. The student will also
benefit from having some familiarity with food microbiology and
environmental investigation techniques but will be likely to rely
heavily on others with greater expertise in these areas in a real-life
outbreak situation.

**Teaching materials required:** graph paper, calculator

**Time required:** approximately 2 hours and 30 minutes

**Language:** English

**Level of case study:** Basic Intermediate [X]{.underline} Advanced

**Materials borrowed from:**

"Foodborne Illness Investigation and Control Reference Manual",
Massachusetts Department of Public Health, Division of Epidemiology and
Immunization, Division of Food and Drugs, and Division of Diagnostic
Laboratories (1997)

"Guidelines for the Investigation and Control of Foodborne Disease
Outbreaks", World Health Organisation, Food Safety Unit Division of Food
and Nutrition and Division of Emerging and Other Communicable Diseases
Surveillance and Control (DRAFT, 1999)

**Reviewed by:**

Richard Dicker, MD, MPH, Centers for Disease Control and Prevention

Steve Luby, MD, Centers for Disease Control and Prevention

Rob Tauxe, MD, MPH, Centers for Disease Control and Prevention

Chris Zahniser, RN, MPH, Centers for Disease Control and Prevention

David Swerdlow, MD, Centers for Disease Control and Prevention

Sharon McDonnell, MD, MPH, Centers for Disease Control and Prevention

Thomas Grein, MD, MPH, World Health Organization

Allison Hackbarth, MPH, Massachusetts Department of Public Health

Denise Werker, MD, MHSc, FRCPC, Laboratory Centre for Diseases Control,
Health Canada

John Sarisky, RS, MPH, Centers for Disease Control and Prevention

**Cover art by:** Barbara Orisich, MS

**Training materials funded by:** the Centers for Disease Control and
Prevention (National Center for Infectious Diseases, Food Safety
Initiative, Public Health Practice Program Office, and Epidemiology
Program Office/Division of International Health)

**INSTRUCTOR'S VERSION**

**Botulism in Argentina**

+-----------------------------------------------------------------------+
| **Learning objectives:**                                              |
|                                                                       |
| After completing this case study, the student should be able to:      |
|                                                                       |
| 1.  describe outbreak situations in which acute control measures      |
|     should be undertaken                                              |
|                                                                       |
| 2.  communicate information on an outbreak or outbreak investigation  |
|     and write a press release                                         |
|                                                                       |
| 3.  given the leading hypothesis(es) in an outbreak, develop a        |
|     questionnaire                                                     |
|                                                                       |
| 4.  given details on the origin, distribution, and preparation of an  |
|     implicated food item, identify critical points for the control of |
|     contamination and microbial survival and growth                   |
|                                                                       |
| 5.  discuss possible barriers to implementation of specific           |
|     interventions following an outbreak investigation                 |
|                                                                       |
| 6.  describe measures that can be used to monitor the success of an   |
|     intervention                                                      |
|                                                                       |
| 7.  describe the occurrence, signs and symptoms, and control of       |
|     foodborne botulism                                                |
+-----------------------------------------------------------------------+

**PART I - OUTBREAK DETECTION**

Foodborne botulism is a severe illness that results from the ingestion
of a preformed toxin produced by a bacterium, *Clostridium botulinum*,
in contaminated food. Death can occur in up to 60% of untreated cases;
supportive care and prompt administration of antitoxin have reduced
mortality in the United States to less than 10%. Outbreaks of botulism
have been linked to improperly preserved vegetables, fruits, and meats
including fermented fish products, sausages, smoked meat, and seafood.

On January 13, 1998, an infectious diseases physician at a Buenos Aires
hospital telephoned the Directorate of Epidemiology of the Argentine
Ministry of Health (MOH) to report two possible cases of botulism. The
patients, both men, presented with drooping eyelids, double vision,
difficulty swallowing, and respiratory problems. One patient had onset
of symptoms on January 5 and the other on January 6. The physician had
drawn sera and collected stool specimens from the men to test for
botulinum toxin but no results were available.

[Question 1:]{.underline} As a public health practitioner in Argentina,
what are the major concerns raised by these two possible cases of
botulism in Buenos Aires?

Because cases of foodborne botulism can be very severe and result from
ingestion of contaminated food that may still be available to cause
illness in others, a single case of foodborne botulism represents a
public health emergency that might herald a larger outbreak.

Public health actions resulting from a suspected case of botulism
include an immediate search for other possible cases and identification
of suspected food exposures, as well as confirming the diagnosis.
Diagnostic testing of both case specimens and foods should be performed
as needed.

*(NOTE: In this outbreak, another public health issue became apparent.
As will be seen, the affected individuals were bus drivers. They
continued to drive their routes although they had double vision and
drooping eyelids. These vision difficulties could have resulted in
unsafe driving practices and, ultimately, motor vehicle accidents.*)

The clinical syndrome of botulism is dominated by neurologic signs and
symptoms. Dryness of the mouth, drooping eyelids, and blurred and double
vision are usually the earliest neurologic complaints. These initial
symptoms may be followed by disturbances in speech, difficulties
swallowing, and peripheral muscle weakness. If respiratory muscles are
involved, ventilatory failure and death may result unless supportive
care is provided. The average incubation period for botulism is 18-36
hours, but symptoms can occur as early as six hours or as late as 10
days after exposure.

Because botulism is rare, many physicians are unfamiliar with its
presentation. As a result, patients with botulism can be misdiagnosed as
other illnesses (e.g., stroke, myasthenia gravis, Guillain‑Barré
syndrome) delaying the administration of life-saving botulinum antitoxin
for days and increasing the mortality rate among cases.

[Question 2:]{.underline} How might you go about swiftly determining if
there are other cases of botulism associated with the cases in Buenos
Aires?

*Additional cases of botulism may be identified through the following
means: (list is in order of likely productivity)*

1.  *talk with patients to identify common meals/foods and other persons
    who may have shared in them*

2.  *talk with family members and friends of cases who may have shared
    meals with the cases and ask if any have signs/symptoms of botulism*

3.  *talk with co-workers who may have shared meals with the cases and
    ask if any have signs/symptoms of botulism*

4.  *contact local hospitals and emergency rooms, describe
    signs/symptoms suggestive of botulism, and ask that all similar
    cases of acute neurologic illness be reported to the MOH*

5.  *review admission and emergency room logs at local hospitals for
    patients with admitting diagnoses suggestive of an acute neurologic
    disease (e.g., stroke, myasthenia gravis, Guillain-Barré syndrome)
    and follow-up suspicious patients to determine if botulism is a
    possibility*

6.  *contact local physicians (especially neurologists), describe
    signs/symptoms suggestive of botulism, and ask that all similar
    cases of acute neurologic illness be reported to the MOH*

7.  *contact area laboratories that do testing for botulism and ask to
    be notified of all requests for botulism testing (e.g.,
    demonstration of toxin in serum, stool, gastric aspirate, and food
    or culture of [C.]{.underline} [botulinum]{.underline} from gastric
    aspirate or stool) (NOTE: Few laboratories do testing for botulism;
    therefore, this may be an unlikely source for identifying cases.)*

8.  *notify the public of the outbreak through various forms of media
    (e.g., newspapers, radio, television)*

The Directors of the National Laboratory and the Environmental Health
and Sanitation Program were notified of the possible cases of botulism.
The two patients, still in the hospital, were interviewed by an MOH
epidemiologist.

Upon questioning, it was learned that both patients were drivers for the
same bus company and drove the same route and shift. The patients knew
each other but worked on different days of the week. They had not eaten
together in more than a month.

To find additional cases, the MOH contacted all employees of the bus
company with the ill drivers to see if any had symptoms suggestive of
botulism. Hospitals in the area of Buenos Aires, where the two cases
occurred, were asked to report any patients with acute neurologic
illnesses that could be botulism. Family members of cases were
questioned about whether they also had symptoms of botulism.
Additionally, the MOH developed a press release for distribution to the
local news media.

[Question 3A:]{.underline} What key points would you include in the
press release?

*In writing a press release, it is important to consider the purpose of
the release and who will be reading it. As a start, one might want to
identify the 2-3 messages to be covered. One would then want to outline
the "what", "who", when", "where", and "why" of the story/issue.*

*In this situation, the purpose of the press release is to identify
additional cases of botulism which might be connected to the two cases
reported by the infectious diseases physician. One might want to include
the following items in the press release:*

1.  *the fact that two cases of a potentially fatal disease were
    diagnosed in the local community (and the dates of illness onset and
    location within the city)*

2.  *the need to identify additional cases so that the individuals can
    be adequately treated*

3.  *the need to find additional cases so an investigation can be
    undertaken, the source of the outbreak can be determined, and the
    implicated product can be recalled and destroyed*

4.  *signs and symptoms of botulism and the most likely sources of
    intoxication*

5.  *a contact name (and telephone number) who can answer questions*

6.  *where to go if a person thinks s/he is a case*

*NOTE: A "Question and Answer Sheet" ("Q & A") is often prepared in
concert with a press release to help handle the influx of calls and
questions.*

[Question 3B:]{.underline} Who should be involved in developing the
press release or notified before its distribution?

*In developing a press release, it is important to consider both
in-house procedures and the politics of the broader public health and
medical community. The MOH should not unilaterally distribute a press
release but should consult with a variety of persons and agencies to
make them aware of the situation, take advantage of their expertise and
resources, and gain their support in addressing the outbreak, if
necessary. Persons/agencies to notify include:*

1.  *the Minister of Health (and other appropriate supervisors within
    the Ministry)*

2.  *communications/public relations staff at the MOH*

3.  *staff at the public health laboratory who may be involved in
    testing of clinical or food specimens*

4.  *the local health department where the terminal stop of the bus
    route is located*

5.  *management from the bus company*

6.  *professional groups (e.g., educational bodies, university staff)*

7.  *national and international public health authorities and reference
    laboratories (e.g., the World Health Organisation \[WHO\], the
    Centers for Disease Control and Prevention \[CDC\])*

8.  *food regulatory agencies (e.g., U. S. Food and Drug Administration
    \[FDA\])*

On January 14, the MOH distributed the following press release:[^1]

*On Monday, January 13, two bus drivers, Pablo Esteban and Juan Rojas,
from south central Buenos Aires were diagnosed with botulism by an
infectious diseases physician at Hospital F. J. Muñiz. The men had been
ill for several days before the diagnosis was made. The attending
physician, Dr. Jorge San Juan reported that botulinum antitoxin was
requested from the U. S. Centers for Disease Control and Prevention last
night.*

> *Because botulism is potentially fatal if untreated, the Argentine
> Ministry of Health is working with local public health officials and
> health care providers to identify*
>
> *the source of the botulism. Officials worry that other persons may
> have been exposed and need treatment or that the source may still
> exist and cause more people to become ill.*
>
> *Botulism is a rare but serious paralytic illness caused by a nerve
> toxin produced by a bacterium, [Clostridium]{.underline}
> [botulinum]{.underline}. The symptoms of botulism can easily be
> confused with other illnesses and include diplopia, ptosis, dysphagia,
> dysarthria, and muscle weakness. If untreated, these symptoms may
> progress to cause paralysis of the arms, legs, trunk and respiratory
> muscles, and ultimately death. If diagnosed early, botulism can be
> treated with an antitoxin which blocks the action of the toxin
> circulating in the blood.*
>
> *Previous outbreaks of botulism in Argentina have been caused
> primarily through eating improperly preserved vegetables and meats.
> Implicated foods include ham, red and green peppers, vigcacha (an
> Andean rodent), eggplant, cucumbers, palm hearts, tomatoes, peaches,
> spinach, and a type of cheese with onions. It is not yet known what
> specific food may have caused the botulism in this outbreak but both
> men are bus drivers for the same company, Arriba Bus, Inc., and drive
> the same route and shift.*
>
> *Persons who feel they or their relatives might have symptoms of
> botulism are asked to contact the Directorate of Epidemiology of the
> Argentine Ministry of Health at xxxx-xxxx .*

[Question 4:]{.underline} Critique the press release. How might the
press release impact the outbreak investigation?

*A press release should be brief (1-2 double spaced pages) and simply
written; it should be written at a level understandable to the general
public (i.e., 5-8th grade reading level), not include jargon or
technical terminology, or assume that the reader has any prior knowledge
of the subject that is being discussed. A press release does not need to
read like a finely crafted article, but it should be written to get the
reporter's interest and provide the facts necessary for a subsequent
article to be developed. To grab the reporter's attention, one should
probably put the most important information up front in the release;
details (or the explanation of the most important points) should
follow.*

*Critique of above press release:*

1.  *The press release is relatively long. Deletion of a number of
    sentences would make it more readable without interfering with its
    goals.*

2.  *The use of patient names in the first paragraph compromises their
    confidentiality. Agency confidentiality policies should be
    considered before releasing patient names and other identifiers.*

```{=html}
<!-- -->
```
1.  *The statements about getting botulinum antitoxin from CDC and the
    description of MOH activities are good. It reassures the community
    that something is being done.*

```{=html}
<!-- -->
```
1.  *The use of medical terminology (e.g., diplopia, ptosis, dysphagia)
    and jargon will prevent many readers from understanding the common
    symptoms of botulism.*

```{=html}
<!-- -->
```
1.  *The press release, if published, could introduce several biases in
    future studies:*

> *[Selection bias:]{.underline}*

*- Bus drivers from Arriba Bus, Inc. (particularly, those from the
morning shift) might be more likely to seek medical attention and be
diagnosed with botulism than other cases.*

*- Physicians might be more likely to test for botulism among bus
drivers from Arriba Bus, Inc. than persons in other occupations who have
similar symptoms.*

> *[Information bias:]{.underline}*

*- Persons diagnosed with botulism might be more likely to recall eating
the food items mentioned as sources of botulism in the news release.*

1.  *Directing all calls to the MOH could be a mistake. The signs and
    symptoms of botulism are non-specific and could be consistent with a
    number of different neurologic maladies in the community. Such a
    request could result in a deluge of calls to the MOH which may not
    be in a good position to examine the individuals or arrange for
    treatment. It might be better to have individuals consult their
    physicians who can make the diagnosis, initiate appropriate care,
    and report to the MOH. It would be appropriate to direct calls from
    the media (i.e., reporters) to the MOH if clarification of the press
    release is needed.*

Seven additional patients with neurologic signs consistent with botulism
were identified. Five of the patients had sought medical attention and
four were hospitalized. Working diagnoses for these patients at the time
the initial two cases were discovered included myasthenia gravis (1),
Guillain-Barré syndrome (2), stroke (1), and diabetic complications (1).

Botulinum toxin was identified in sera and/or stool from three patients,
including one of the original cases reported on January 13.

All patients were drivers from the same bus company as the original
cases and drove the same route. From initial reports, all had eaten at a
home located at the terminal stop of the bus route where the drivers
stopped during their breaks. Approximately 58 bus drivers worked this
route; 27 in the morning shift, 16 in the afternoon shift, and 15 in the
evening shift.

[Question 5:]{.underline} Would you initiate any control measures at
this time? What criteria would you consider in implementing control
measures so early in an investigation?

*Epidemiologists often want to delay implementation of specific control
measures until more definitive information on the source of the outbreak
and mode of transmission are available (e.g., results from a
case-control or cohort study). Although usually a wise approach, obvious
control measures [should not be delayed]{.underline} because
investigations are still underway. If sufficient information is
available to prevent additional cases of a foodborne disease, then one
must act!*

*Information which might lead the outbreak investigation team into
taking action when data are suggestive but insufficient to make a
definitive call include:*

1.  *the severity of the disease (e.g., [E. coli]{.underline} O157:H7,
    botulism) (i.e., one may be moved to act more quickly with a very
    serious or potentially fatal disease than one which is mild or
    self-limiting)*

2.  *the population at risk (e.g., infants, immunocompromised persons,
    the elderly)(i.e., if the population at risk includes persons who
    are highly likely to have poor outcomes from the
    infection/intoxication, then one may be moved to act more quickly)*

3.  *whether exposure is suspected to still be occurring*

4.  *how easily control measures can be implemented (e.g., does control
    require a nationwide recall of a commercially distributed product or
    temporary removal of one foodhandler?)*

*In this outbreak, one might argue that the severity of the illness
increases the urgency for action. At a minimum, one would want to
follow-up on the 58 bus drivers to make sure no other drivers were ill
and that ill persons were receiving appropriate treatment. In addition,
one would probably want to follow-up on the terminal home of the bus
route, the owners, its workers, and other customers to see if they were
ill. Given the nature of the outbreak (i.e., a very serious disease for
which exposure might be ongoing), one should consider suspending
commercial food services at the home (or asking the home to voluntarily
suspend services) until more information can be collected.*

**PART II - DESCRIPTIVE EPIDEMIOLOGY AND HYPOTHESIS GENERATION**

Staff from the local health department where the terminal stop of the
bus route was located were invited to participate in the investigation.

Physicians attending the cases of botulism were asked to provide
demographic and clinical information on their patients. (Table 1)

Table 1. Characteristics of cases of botulism, Buenos Aires, January
1998.

  --------- --------- -------- --------- ------------- -------------------------
  Patient   Age       Gender   Work      Onset of      Symptoms
  No.       (years)            shift     neuro-logic   
                                         symptoms      

  1         42        M\*      Morning   January 6     blurred vision, double
                                                       vision, drooping eyelids,
                                                       upper and lower extremity
                                                       weakness, respiratory
                                                       difficulty, fatigue

  2         31        M        Morning   January 5     blurred vision, double
                                                       vision, drooping eyelids,
                                                       upper and lower extremity
                                                       weakness

  3         23        M        Morning   January 9     blurred vision, drooping
                                                       eyelids, upper extremity
                                                       weakness, fatigue

  4         46        M        Morning   January 8     drooping eyelids,
                                                       difficulty speaking

  5         54        M        Morning   January 5     blurred vision, double
                                                       vision, drooping eyelids,
                                                       difficulty speaking,
                                                       respiratory difficulty

  6         49        M        Morning   January 10    blurred vision, drooping
                                                       eyelids, difficulty
                                                       speaking

  7         31        M        Morning   January 15    blurred vision, double
                                                       vision, drooping eyelids,
                                                       upper and lower extremity
                                                       weakness, respiratory
                                                       difficulty, fatigue

  8         44        M        Morning   January 14    respiratory difficulty,
                                                       fatigue, drooping
                                                       eyelids,

  9         24        M        Morning   January 12    drooping eyelids, fatigue
  --------- --------- -------- --------- ------------- -------------------------

\*M=male gender

[Question 6A:]{.underline} Summarize the demographic and clinical
information on these patients and draw an epidemic curve.

*All patients were male and all were bus drivers from the same company
working on the morning shift of the same route. The median age of cases
was 42 years (range: 23-54). All patients had drooping eyelids (ptosis).
Six patients had blurry vision; five had fatigue; four each had double
vision (i.e., diplopia), upper extremity weakness, and respiratory
difficulty; three had lower extremity weakness. Onset of neurologic
symptoms occurred from January 5 through January 15. Cases did not peak
at any particular point during the 11-day period.*

![](media/image1.png){width="6.0in" height="3.5in"}*Figure 1. Onset date
of neurologic symptoms among patients with botulism in Buenos Aires,
Argentina, January 1998. (N=9)*

[Question 6B:]{.underline} When was the most likely period of exposure
among these cases?

*As noted above, the average incubation period for botulism is 18-36
hours, but symptoms can occur as early as six hours or as late as 10
days after exposure. The following two methods can help determine the
time of exposure if dates of onset of symptoms are known:*

*[Method #1:]{.underline} If a point source is suspected and the
organism and time of onset of illness are known, 1) identify the last
known case in the outbreak and count back the maximum incubation*

*period and 2) identify the first case and count back the minimum
incubation period. Ideally, the dates should be similar and represent
the probable period of exposure. Using this technique, the period of
exposure for this outbreak would be January 4-5. However, at this point,
it is unknown if the exposure occurred on one day or over a more
extended period of time. Therefore, one would consider a slightly longer
period of exposure in exploring possible sources of the outbreak.*

*[Method #2:]{.underline} If a point source is suspected and the
organism and time of onset of illness are known, count back the median
incubation period from the peak of the outbreak. Looking at the epidemic
curve for this outbreak, cases do not cluster at any obvious point in
time; therefore, it might be more difficult to use this technique to
identify the exposure period.*

In hypothesis-generating interviews with cases and other bus drivers,
being a driver on the morning shift of the bus route and eating at the
terminal home of the route were the only common exposures among cases.
No cases of botulism occurred among bus drivers from the afternoon or
evening shift of the route. Bus drivers from those shifts did not
usually eat at the terminal home because it was only open for lunch.

The investigators hypothesized that the outbreak was limited to morning
shift bus drivers and resulted from eating or drinking something at the
home at the terminal stop of the particular bus route between January 3
and 7.

[Question 7:]{.underline} What type(s) of study would you use to
investigate this hypothesis? Why?

*To test the hypothesis, one would want to compare specific exposures
among persons who became ill with those among persons who did not become
ill. One could use either a cohort or case-control study to explore this
hypothesis. Because the outbreak is confined to a well-defined and
relatively small group of individuals (i.e., 27 bus drivers on a
particular route and shift), a cohort study would seem most logical. A
cohort study would also permit investigators to calculate attack rates.*

*In addition to epidemiologic studies, other studies may be of use
(e.g., collection and testing of food samples, environmental
investigations, or exploration of food preparation methods at the
terminal home). Results from each of these studies could provide
important information on the source of the outbreak and the necessary
means to control it.*

*Should one undertake the epidemiologic study first or the other
studies? The epidemiologic investigation can often focus subsequent
investigations; however, on certain occasions, other studies must be
initiated first or simultaneously (e.g., the collection of food
specimens which might be discarded). Therefore, the order of various
investigations will depend largely on the specifics of the outbreak.*

**PART III - DESIGNING AN EPIDEMIOLOGIC STUDY TO TEST THE HYPOTHESIS**

To identify the source of the outbreak, investigators undertook a
retrospective cohort study among bus drivers who drove the morning shift
of the bus route. Data were collected from January 15-19.

Investigators defined a confirmed case of botulism as a bus driver from
the morning shift of the bus route with a serum or stool sample that
demonstrated botulinum toxin or yielded *Clostridium botulinum* with
onset of symptoms between January 5 and 15. A probable case was defined
as acute cranial nerve dysfunction (e.g., blurred vision, double vision,
drooping eyelids, problems swallowing) with no laboratory confirmation
in this group of drivers during the same period. The comparison group
consisted of all bus drivers from the morning shift of the implicated
bus route who had no acute neurologic symptoms suggestive of botulism.

After consultation with the local health department where the terminal
stop of the bus route was located and the bus company management,
investigators developed a structured questionnaire for the epidemiologic
study.

[Question 8:]{.underline} What general types of information would you
include in the questionnaire?

1.  *[Identifying information]{.underline} (e.g., name, medical record
    number, code number). This information allows the investigator to
    identify the patient and update the questionnaire as more
    information becomes available. It also prevents duplicate entry of
    records.*

```{=html}
<!-- -->
```
1.  *[Demographic information]{.underline} (e.g., age, gender,
    race/ethnicity, location). This information is basic to all
    descriptive epidemiology allowing one to characterize the population
    at risk and examine possible confounders.*

```{=html}
<!-- -->
```
1.  *[Clinical information]{.underline} (e.g., sign/symptoms, time of
    onset of illness, laboratory results, whether the patient saw a
    doctor or was hospitalized). This information allows one to confirm
    the diagnosis, characterize the disease, and chart the course of the
    outbreak.*

```{=html}
<!-- -->
```
1.  *[Risk factor information]{.underline} (e.g., foods eaten,
    underlying medical illnesses, routine medications). This information
    allows one to explore the source of the outbreak.*

2.  *[Source of the information]{.underline} (e.g., patient, parent,
    spouse, physician). This information will provide some insight into
    the accuracy of the information obtained.*

[Question 9:]{.underline} What steps would you take to develop the
questionnaire for this investigation.

*Although there are no set steps for developing a questionnaire for an
epidemiologic study, one would probably go through the following thought
processes:*

1)  *Identify the primary and secondary hypothesis for the source of the
    outbreak.*

2)  *List the discrete pieces of information needed to accept or reject
    the primary and/or secondary hypotheses. This includes clinical
    information to distinguish cases from controls and exposure
    information. (For this outbreak, it would be useful to obtain
    detailed menus of foods served or talk with the chef to determine
    what was truly served.)*

3)  *List information that is needed for the logistics of the study
    (e.g., subject name, address, study number, interviewer name) or to
    control for potential confounders (e.g., age, race, sex, location).*

4)  *Identify how the collected information will be used to test the
    hypothesis (i.e., plan analysis including dummy tables of key
    variable).*

5)  *Write the questions to collect the information. (One will need to
    consider the most appropriate format and wording of the questions.
    It might also be helpful to consult with other jurisdictions that
    have had similar outbreaks and obtain questionnaires they used.)*

6)  *Organize the questions into questionnaire format and develop
    introductions/closings and possible responses for close-ended
    questions. (One may need to consult with key informants or conduct
    focus groups to determine the most appropriate responses for the
    setting and community.)*

7)  *Pre-test the questionnaire.*

8)  *Revise the questionnaire.*

9)  *Train interviewers, if used.*

[Question 10:]{.underline} Using information on foods served at the
terminal stop home from January 3-7 (Appendix 1), draft questions for
food exposure for this study.

*Two important issues to consider in developing these questions:*

1)  *Multiple exposures during the 5-day period. Some persons may have
    eaten at the terminal home on more than one occasion. To address
    this, one might wish to:*

-   *collect information on foods eaten each day during the period of
    interest*

-   *ask whether a particular item was eaten at any time during the
    period of interest*

-   *ask "how many times" a particular item was eaten during the period
    of interest*

> *(In some situations, it may be appropriate to ask "how much" was
> eaten since risk may increase with dose.)*

2\) *Responses to multiple choice or "Yes/No" questions. Responses
should include a "Don't know" category. This allows investigators to
distinguish between the respondent not knowing the answer to a question
and the respondent overlooking or purposefully skipping a question. To
encourage study subjects to answer questions, many investigators use the
following instructions (or a close facsimile), "We know it can be
difficult to remember what you ate more than a few days ago. Please make
your best guess as to whether you ate any of the following food items.
It might be useful to look at a calendar to help you remember what foods
you have recently eaten."*

*The following questions were used by the study investigators:*

Did you eat or drink any foods at the terminal house on your route
between Saturday, January 3 and Wednesday, January 7?

> *YES NO Do not know*

*If NO, finish the questionnaire\...*

> *If YES\....*
>
> *On Saturday, January 3, at the terminal house on your route, did you
> eat or drink \...*
>
> *a. black coffee? YES NO Do not know*
>
> *b. coffee with milk? YES NO Do not know*
>
> *c. tea? YES NO Do not know*
>
> *d. soda pop? YES NO Do not know*
>
> *e. mate? YES NO Do not know*
>
> *f. ham sandwich? YES NO Do not know*
>
> *g. processed ham sandwich? YES NO Do not know*
>
> *h. matambre sandwich? YES NO Do not know*
>
> *Did you eat the filling in the matambre? YES NO Do not know*

*i. hot dog? YES NO Do not know*

> *j. salami? YES NO Do not know*
>
> *k. bologna? YES NO Do not know*

*l. sauce? YES NO Do not know*

*m. other foods? YES NO Do not know*

> *\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_*
>
> *\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_*

These questions were repeated for each day from January 3 - January 7.

Investigators conducted interviews with each of the drivers of the
morning shift of the bus route to complete the questionnaires.

[Question 11:]{.underline} If the investigators had decided on
self-administration of the questionnaire, what changes might need to be
made to it?

*Method of administration plays a large role in both the wording and
organization of a questionnaire. For a self-administered questionnaire
(or one in which you use a person less familiar with the issues to
collect the information \[e.g., a translator\]), no one will be
available to define vocabulary, provide guidance on navigation through
the questionnaire, or encourage the subject to complete the entire
questionnaire. Therefore, one might want to focus attention on the
following:*

11. *The wording of each question should be easily understood and free
    of technical words or jargon.*

12. *Use of abbreviations should be limited to those readily known to
    all study subjects.*

13. *When creating potential responses for closed-ended questions,
    anticipate and prepare for all possibilities. Make sure responses
    are mutually exclusive and easily understood. Be sure to include a
    "Don't know" category.*

14. *Means of entering/selecting responses should be as simple as
    possible (and explained if necessary) (e.g., some subjects may not
    know how to enter a date into six blanks).*

15. *Skip patterns should be kept to a minimum and should be clearly
    described.*

16. *The questionnaire should be as short as possible.*

*(NOTE: Most of the above are also important issues for other forms of
questionnaire administration but may be more critical with
self-administered questionnaires or ones in which you use a person less
familiar with the issues or epidemiology to gather the data.)*

*Pretesting the questionnaire with persons who are similar to study
subjects will help identify and correct potential problems before it is
too late.*

**PART IV - ANALYSIS AND INTERPRETATION OF EPIDEMIOLOGIC RESULTS**

The following food exposure information was collected through the cohort
study. On January 19, the information was tabulated by epidemiologists
from the Argentine MOH. (Table 2)

Table 2. Foods eaten by ill and well bus drivers at the home at the
terminal bus stop, January 3-7, 1998. (N=21)

  ------------------------- --------- ------------ --------- -------------
  Food item                 Ate item               Did not   
                                                   eat item  

                            Ill       Well         Ill       Well

  Bologna                   1         0            8         12

  Hot dog                   1         1            8         11

  Matambre\*                9         2            0         10

  Mate\*\*                  4         4            5         3

  Processed Ham             2         3            7         9

  Sauce                     7         2            2         10

  Salami                    1         1            8         11

  Solid ham                 2         3            7         9
  ------------------------- --------- ------------ --------- -------------

\*Matambre is a traditional meat roll in Argentina.

\*\*Mate is green tea.

[Question 12:]{.underline} Calculate the appropriate measures of
association for these exposures.

*The appropriate measure of association for a cohort study is the
relative risk. The relative risk (RR) reflects the excess risk (of
disease) in the exposed group compared with the unexposed group.*

  ------------- ------------ ------------ --------------------------------
                *Ill*        *Well*       *TOTAL*

  *Exposed*     *a*          *b*          *(a+b)*

  *Unexposed*   *c*          *d*          *(c+d)*

  *TOTAL*       *(a+c)*      *(b+d)*      *t*
  ------------- ------------ ------------ --------------------------------

*relative = [attack rate among persons who ate item ]{.underline}*

*risk attack rate among persons who did not eat the item*

*= [\# of ill persons who ate item/total \# of persons who ate
item]{.underline}*

*\# of ill persons who did not eat item/total \# of persons who did not
eat item*

*= [a/(a + b)]{.underline}*

*c/(c + d)*

*NOTE:*

*A relative risk of 1.0 means the risk of disease is similar in the
exposed and unexposed group and exposure is not associated with
disease.*

*A relative risk of greater than 1.0 means the risk of disease is
greater in the exposed than the unexposed group and the exposure could
be a risk factor for the disease.*

*A relative risk of less than 1.0 means the risk of disease is less in
the exposed group than the unexposed group and the exposure could be a
protective factor.*

*Tests of statistical significance (such as the chi-square or Fisher
exact test) are used to determine how likely it is that the observed
relative risk could have occurred by chance alone, if exposure was not
actually related to the disease. This probability is the p-value. A very
small p- value means that one would be unlikely to observe such an
outcome if indeed there was no association between the exposure and the
disease. If the p-value is smaller than some predetermined cutoff
(usually 0.05 or 5 in 100 chance), the association is then said to be
"statistically significant".*

*To calculate a chi-square using above data layout and notation:
(optional)*

*^2^ = [t(ad-bc - t/2)^2^ ]{.underline}*

*(a+b)(c+d)(a+c)(b+d)*

*NOTE: The instructor may wish to divide up the calculations among the
students to limit the amount of time this exercise takes. One student
can be asked to explain how s/he calculated their relative risk. The
remaining students can just share their answers.*

*The calculations for the food items served at the terminal home of the
bus route are:*

+------------+----+-----+------+-----+-----+------+--------+------+
| *Food      | *A |     |      | *   |     |      | *Rel   | *    |
| item*      | te |     |      | Did |     |      | ative* | p-va |
|            | i  |     |      | not |     |      |        | lue* |
|            | te |     |      | eat |     |      | *Risk* |      |
|            | m* |     |      | it  |     |      |        |      |
|            |    |     |      | em* |     |      |        |      |
+------------+----+-----+------+-----+-----+------+--------+------+
|            | *  | *We | *Att | *I  | *We | *At  |        |      |
|            | Il | ll* | ack* | ll* | ll* | tack |        |      |
|            | l* |     |      |     |     | R    |        |      |
|            |    |     | *R   |     |     | ate* |        |      |
|            |    |     | ate* |     |     |      |        |      |
+------------+----+-----+------+-----+-----+------+--------+------+
| *Bologna*  | *  | *0* | *1   | *8* | *   | *    | *2.5*  | *0   |
|            | 1* |     | 00%* |     | 12* | 40%* |        | .43* |
+------------+----+-----+------+-----+-----+------+--------+------+
| *Hot dog*  | *  | *1* | *    | *8* | *   | *    | *1.2*  | *    |
|            | 1* |     | 50%* |     | 11* | 42%* |        | 1.0* |
+------------+----+-----+------+-----+-----+------+--------+------+
| *Matambre* | *  | *2* | *    | *0* | *   | *0%* | *unde  | *0.0 |
|            | 9* |     | 82%* |     | 10* |      | fined* | 002* |
+------------+----+-----+------+-----+-----+------+--------+------+
| *Mate*     | *  | *4* | *    | *5* | *3* | *    | *0.8*  | *    |
|            | 4* |     | 50%* |     |     | 63%* |        | 1.0* |
+------------+----+-----+------+-----+-----+------+--------+------+
| *Processed | *  | *3* | *    | *7* | *9* | *    | *0.9*  | *    |
| Ham*       | 2* |     | 40%* |     |     | 44%* |        | 1.0* |
+------------+----+-----+------+-----+-----+------+--------+------+
| *Sauce*    | *  | *2* | *    | *2* | *   | *    | *4.6*  | *0.  |
|            | 7* |     | 78%* |     | 10* | 17%* |        | 009* |
+------------+----+-----+------+-----+-----+------+--------+------+
| *Salami*   | *  | *1* | *    | *8* | *   | *    | *1.2*  | *    |
|            | 1* |     | 50%* |     | 11* | 42%* |        | 1.0* |
+------------+----+-----+------+-----+-----+------+--------+------+
| *Solid     | *  | *3* | *    | *7* | *9* | *    | *0.9*  | *    |
| ham*       | 2* |     | 40%* |     |     | 44%* |        | 1.0* |
+------------+----+-----+------+-----+-----+------+--------+------+

*NOTE: The relative risk for matambre is undefined. This is because
among persons who did not eat the matambre, no one became ill (i.e., the
attack rate is zero among persons not eating matambre.) For the
calculation of the relative risk, this would mean the denominator is
"0\" and division by "0\" is undefined.*

[Question 13:]{.underline} Interpret the results. What further data
analysis/information might help?

*\[Unlike the original investigation and real life, we have included
"sauce" as a menu item that has an elevated relative risk.\]*

*Among the foods consumed between January 3 and 7, only matambre, a
traditional meat roll (prepared from meat, vegetables, spices, and eggs)
and "sauce" were significantly associated with illness. All ill persons
ate matambre. Furthermore, 82% of persons eating matambre became ill,
whereas none of the 10 persons who did not eat matambre became ill.
Almost all of the persons who ate sauce became ill (78%); however, two
ill persons did not eat the sauce.*

*The question, at this point, is whether both the matambre and the sauce
were contaminated with botulinum toxin, if one cross-contaminated the
other, or if only one of the items was contaminated but both were
routinely served together (and rarely apart). It would be of interest to
ask how the sauce and matambre were usually prepared and served. One
would also want to*

*collect any leftover specimens of both items to search for botulinum
toxin. A stratified analysis, to examine only individuals who ate one of
these items but not the other, might also be of interest. (However,
numbers may be very small.)*

*As it turns out, the sauce was not contaminated but just served
routinely with the implicated matambre.*

**PART V - ENVIRONMENTAL STUDIES AND FOOD INVESTIGATION**

Matambre is a traditional Argentine dish prepared from meat, vegetables,
spices, and eggs. In a traceback of the implicated matambre, the MOH
discovered that it originated from a small scale producer located not
far from the terminal stop of the bus route. The matambre was purchased
at a local market on January 3 by the owners of the home that served the
matambre. The MOH initiated an environmental health assessment of the
matambre to identify production factors that could have contributed to
the occurrence of botulism.

A complete environmental health assessment is not a cursory inspection
of operations and sanitary conditions as is performed for the licensing
of a food establishment, but focuses on the suspect food or meal and
follows it from its raw ingredients to consumption by the customer. The
objective of the environmental health assessment is to identify critical
points where the implicated food could have become contaminated or
microbial survival and growth in the food could have occurred, determine
why these conditions existed, and identify appropriate interventions.
The factors in Table 3, often found in these assessments, have been
associated with an increased risk of foodborne disease.

Table 3. Factors that commonly contribute to outbreaks of foodborne
diseases, from Bryan et al., 1987.

+-----------------------+-----------------------+-----------------------+
| Contamination         | Survival              | Growth                |
+-----------------------+-----------------------+-----------------------+
| raw foods that are    | inadequate cooking    | inadequate            |
| contaminated          |                       | refrigeration         |
|                       | inadequate reheating  |                       |
| infected foodhandler  |                       | improper cooling      |
|                       | inadequate            |                       |
| unclean equipment     | acidification         | inadequate            |
|                       |                       | hot-holding           |
| cross-contamination   |                       |                       |
|                       |                       | preparation too far   |
| contaminated foods    |                       | in advance            |
| eaten                 |                       |                       |
|                       |                       | of serving            |
| raw or lightly cooked |                       |                       |
|                       |                       | use of leftover foods |
| inappropriate         |                       |                       |
| container for food    |                       | inadequate            |
|                       |                       | acidification         |
| unsafe sources        |                       |                       |
|                       |                       | high water content    |
| added poisonous       |                       |                       |
| chemicals             |                       | inadequate curing     |
|                       |                       | salt                  |
| natural toxicant      |                       |                       |
|                       |                       | environment that      |
| poor dry-storage      |                       | provides              |
| practices             |                       |                       |
|                       |                       | favorable conditions  |
|                       |                       | for                   |
|                       |                       |                       |
|                       |                       | pathogen (e.g.,       |
|                       |                       | anaerobic             |
|                       |                       |                       |
|                       |                       | packaging)            |
+-----------------------+-----------------------+-----------------------+

[Question 14:]{.underline} What types of activities do you think you
would undertake as part of an environmental health assessment on the
matambre? What equipment would you want to have?

*In the investigation of the matambre, one would want to do the
following:*

1.  *Describe the matambre (e.g., all raw materials and ingredients
    used, source of ingredients, physical and chemical characteristics
    such as pH, intended use).*

2.  *Observe procedures from receipt of ingredients to finished product
    (e.g., cleaning methods, temperature history of the ingredients or
    product as it was stored, transported, cooked, heat-processed, held
    warm, chilled, or reheated).*

3.  *Talk with foodhandlers, managers, and others who may be familiar
    with the food preparation process and facility. Collect information
    on any aspect of the establishment, facilities, equipment, food,
    water, and processes that may have contributed to the outbreak.
    Record observations as well as reported information concerning
    economics, social and cultural beliefs, and management decisions
    that may have influenced or altered the food preparation process.*

4.  *Make appropriate measurements (e.g., time and temperature
    conditions to which the food was exposed, water activity, moisture,
    and pH of suspect food, size of containers used in procedures and
    depth of food in containers).*

5.  *Draw a flow diagram of the operations (e.g., exact flow of
    operations for the suspect food, name of persons performing
    operations, equipment used, results of measurements taken). It may
    be necessary to develop flow diagrams for each food preparer and/or
    shift.*

6.  *Collect appropriate specimens (e.g., leftover samples of the
    implicated food, samples of the ingredients, environmental testing
    of food preparation surfaces or equipment).*

7.  *Collect copies of invoices for the implicated food item or its
    ingredients (e.g., including information about the source of the
    items, batch or lot numbers, dates shipped and received, quantities
    received).*

*To do the above, one would probably need a pencil/pen and paper,
several thermometers (17-104C or 0-220F), a thermocouple, a ruler,
sterile sample containers, sterile sample collection implements (e.g.,
spoons, scoops, spatula, swabs), waterproof labels/tags, sample forms,
refrigerants (e.g., ice packs, heavy plastic bags, insulated
containers), and a camera.*

*Clostridium botulinum* is a spore-forming obligate anaerobic bacterium
(i.e., it cannot grow in the presence of oxygen). The spores are
widespread in soil and dust worldwide. The toxin is produced in
improperly canned, low-acid or alkaline foods and in pasteurized and
lightly cured foods held without adequate refrigeration, especially in
airtight containers. The toxin is destroyed by boiling; inactivation of
spores requires much higher temperatures.

Food safety inspectors from the local health department initiated the
environmental health assessment on January 20. The home at the terminal
stop of the bus route was not formally licensed or equipped as a
restaurant. Perishable foods, such as the matambre, were kept in two
large refrigerators inside the home. Although the refrigerators were set
at the coldest possible setting, temperatures measured inside the
refrigerators were 9C and 10C (48F and 50F, respectively).

The home owner reported the most recent matambre served in the home
weighed approximately 4 kg. The matambre was cut into about 15 slices
and was served in sandwiches, usually with a spicy sauce; no other
condiment or ingredient was added to the sandwiches. No matambre was
available for testing.

The implicated matambre was bought at a local market where it had been
stored in a refrigerator. The market had no temperature records or sales
receipts; however, some customers reported that the matambre had
recently been sold at reduced prices because of power outages.

The market purchased matambre from a small scale commercial producer who
made matambre and processed hams in his home. To make matambre, the
producer placed a slab of raw beef (1- to 3-cm thick) on a stainless
steel table. Ingredients included raw sliced carrots, hard-boiled eggs,
salt, red pepper flakes, dried oregano, and commercial potato flour. The
meat was rolled up around the vegetables and eggs to make an
approximately 10 x 30 cm cylinder. The meat roll was placed into a
rectangular stainless steel pan to keep ingredients inside during
cooking. Between 10 and 15 matambre in individual steel pans were
immersed together in water heated to 70 to 80C (158 to 176F) and
cooked approximately 4 hours. The matambre was never brought to a boil.
After cooking, the water was drained and the temperature was checked to
ensure an internal temperature of about 68C (154F). The producer
placed each warm matambre in plastic wrap, squeezed out the air, and
sealed the plastic with heat. The plastic wrapped matambre were allowed
to cool, placed in a walk-in refrigerator, and were stored for up to 2
weeks before being sold to either supermarkets or directly to consumers.

[Question 15:]{.underline} Identify the foodhandling practices for the
matambre which were most likely to contribute to the development of
botulism.

*Students should consider which of the many problems in the production
of the matambre are critical in the survival of botulinum spores and/or
toxin. Given the microbiologic characteristics of [C.
botulinum]{.underline}, the following factors will put one at higher
risk for botulism:*

1.  *inadequate cooking*

2.  *inadequate reheating*

3.  *long storage time between preparation and consumption*

4.  *anaerobic packaging*

5.  *low acid and high water content*

*These points are shaded in gray in the diagram below. Instructors may
wish to draw Figure 2 on the board as the above description is being
read or share copies with the students.*

*Figure 2. Flow diagram for preparation and serving of matambre,
Botulism Outbreak in Buenos Aires, January 1998.*

![](media/image2.png){width="6.0in" height="4.0625in"}

The producer reported making matambre every 2 weeks in batches of 15-20
each time. The last batch produced before the outbreak was made in early
December. No matambre were available from that batch.

[Question 16:]{.underline} What control measures would you initiate at
this time? What difficulties might you encounter?

*Although testing of the matambre for botulism toxin is not possible,
the following actions should be undertaken based on the epidemiologic
results and supporting environmental investigation:*

1)  *recall and destroy all matambre made by this producer*

2)  *stop further production of matambre by this producer until its
    safety can be assured*

3)  *explore whether other food items made by this producer could also
    be problematic (and, if so, stop production and recall products as
    necessary)*

4)  *assess other facilities preparing matambre to determine if
    problematic practices are more widespread*

*To correct identified deficiencies, one would want to provide education
on appropriate foodhandling procedures to the matambre producer and his
employees, persons at the market where the electrical outages occurred,
and the owner(s) and foodhandlers at the home at the terminal stop of
the bus route. One would also want to ensure that all equipment at these
facilities was in proper working order and apply public health
engineering methods where appropriate. Temporary closure of the three
facilities or more thorough inspections to ensure proper foodhandling
procedures would also need to be considered.*

*Possible problems:*

1.  *Identification and recall of remaining matambre produced by this
    facility could be problematic. It is likely that much of the
    matambre (from the December and subsequent batches) has already been
    sold and consumed; that which remains is likely to be in a number of
    private homes and food service establishments around the area.
    Unless the product is clearly labeled (and distinguishable from
    other locally produced matambre) or the producer has good records on
    distribution and sales, a general recall may not be feasible or
    productive (and could result in widespread panic or damage to the
    reputations/businesses of unimplicated producers).*

```{=html}
<!-- -->
```
1.  *Closure of the facilities could cause local hardships. For
    instance, the home at the terminal stop of the bus route could be
    the only food service establishment available to bus drivers and
    other persons visiting the area. Closure would mean that patrons
    (such as the bus drivers) would need to find other sources of food
    or carry food with them. Cessation of matambre production alone
    would probably not cause the same level of local hardship other than
    the loss of revenue by the producer.*

```{=html}
<!-- -->
```
1.  *Closure of these sites could be an extensive process, depending on
    local regulations and policies. Local health officials may not have
    the authority to close the establishments without due process and
    approval by another local decision making authority (e.g., local
    board of health or city/county council). Facility inadequacies would
    need to be fully documented and presented with other evidence to the
    implicated facilities, themselves, and the local decision making
    authority. Hearings might be needed and opportunities for appeals
    made. Given the serious nature of this outbreak, these hearings
    would presumably occur after the facility was closed. Again,
    cessation of matambre production alone will not be as problematic as
    closing the facilities.*

```{=html}
<!-- -->
```
1.  *More thorough inspection of the facilities may overburden local
    public health resources. All over the world, local health
    departments struggle to complete inspections needed for the purposes
    of licensing and annual renewals. Increasing the time spent during
    routine visits to the facilities may greatly strain local public
    health resources.*

*NONE OF THE ABOVE PROBLEMS SHOULD PREVENT ONE FROM TAKING THE MOST
APPROPRIATE ACTION. However, for a control effort/intervention to
contribute to the public's health, it needs to be acceptable to those
implementing it and able to be implemented with the given resources.*

*At this point, students should be encouraged to insert the matambre
production date into the epidemic curve drawn in Question 6A.*

**PART VI - CONTROL**

After inspection by local food safety officials, the facility producing
the matambre was closed. The producer was unable to provide receipts or
a distribution list with locations where his products were sold. He
reported that most of his clients distributed his products in the
western greater Buenos Aires area. The producer's matambre was not
labeled in any way to indicate the source or date of production, so a
recall of any remaining matambre was not deemed feasible.

Based on data maintained by the MOH, botulism is not an uncommon
occurrence in Argentina. During the years 1979-97, 277 cases of botulism
were reported; for most, the source of the exposure was undetermined. In
1997, 23 patients with suspected botulism were reported (of which 13
\[57%\] died); about the same number of laboratory-confirmed cases were
identified in the United States, which has 10 times the population of
Argentina.

[Question 17:]{.underline} Given the scope of the problem, what longer
term interventions might help decrease the number of botulism cases in
Argentina?

*Many possible interventions exist:*

1)  *more thorough and rapid investigation of individual cases of
    botulism to learn more about usual sources and limit the number of
    persons exposed through any one source*

2)  *improved diagnostic capabilities (e.g., increased provider
    knowledge, improved laboratory resources) to increase the speed of
    diagnosis and the initiation of further investigations*

3)  *placement of more resources into food production facility
    education, licensing, and monitoring, especially for high risk
    foods*

4)  *consultation with food scientists (or targeted research) to
    identify safe ways to produce matambre*

5)  *education of the general public about high risk foods and means to
    prevent botulism*

Because of the relatively high incidence and case fatality ratio for
botulism in Argentina, the MOH and Centers for Disease Control and
Prevention (CDC) collaborated to establish a botulism surveillance and
antitoxin release system in Argentina. The system components
included: 1) the establishment of a local stock of antitoxin, 2) a
mechanism for antitoxin distribution within the country, 3) emergency
notification and response for suspect cases (including urgent
epidemiologic investigation of the possible food source), and 4)
laboratory confirmation of suspect cases.

[Question 18:]{.underline} What is the rationale behind the components
of this control effort?

*The centralized antitoxin supply and single emergency release number at
the MOH are aimed at both a rapid response to each case of botulism and
more effective surveillance of cases over time. Upon receiving a request
for antitoxin, consultation between the treating physician and the MOH
will help in differentiating botulism from many other illnesses, thus
preventing unnecessary antitoxin administration. If the MOH consultant
and the treating physician determine that botulism is a likely
diagnosis, locally held antitoxin can be swiftly dispatched resulting in
more rapid treatment of patients and, hopefully, decreased morbidity and
mortality. The required consultation ensures that a search for
additional cases of botulism and investigation of a food vehicle is
quickly initiated. This will enable the early diagnosis of some exposed
persons and prevent other cases from occurring. The laboratory
confirmation of suspect cases and other surveillance data will allow
public health officials to better understand trends in botulism in
Argentina and allow the identification of more outbreaks and development
of more effective interventions and prevention programs in the future.*

[Question 19:]{.underline} How might you monitor the Argentine botulism
surveillance and antitoxin release system over time to determine if it
is effective?

*The following trends may help evaluate the success of the Argentine
botulism surveillance and antitoxin release system:*

1.  *number of cases of botulism*

2.  *number of cases of botulism for which a food is implicated*

3.  *average number of cases associated with each implicated food item*

4.  *number of cases associated with commercially prepared foods*

5.  *time from diagnosis to administration of antitoxin*

6.  *sequella and complications among cases*

7.  *case-fatality rate*

8.  *number of unsafe foods and food practices identified*

*With a strong surveillance system, decreases in each of these numbers
over time would suggest at least limited success of the program.
Paradoxically, as one implements improved surveillance and outbreak
investigation, the number of identified cases will initially rise. With
consistent data collection and the implementation of appropriate
interventions, however, the numbers will be expected to decrease over
time.*

*Again, students should be encouraged to note the time at which various
control measures/ interventions were implemented (e.g., closure of the
matambre production facility, initiation of surveillance system) on
their epidemic curves. (Figure 3)*

Figure 3. Onset date of symptoms among patients with Botulism in Buenos
Aires, Argentina, December 1997 - January 1998. (N=9)

![](media/image3.png){width="5.989583333333333in"
height="3.7916666666666665in"}

**EPILOGUE**

Although consumption of matambre is an established tradition in
Argentina, it is usually consumed fresh and is not generally intended
for pickling or long-term preservation. Matambre produced by licensed,
commercial facilities use nitrites, acidifiers, or other preservatives
to prevent bacterial growth; the implicated matambre lacked these.
Insufficient cooking, vacuum packing in heat-shrinked wrap, and
inadequate refrigeration may have provided conditions for live spores to
germinate and produce toxin.

The matambre that is believed to be the cause of the outbreak was cooked
at relatively low temperatures (78-80C or 158-176F ) over a time
period of approximately 240 minutes, too short to kill all *C.
botulinum* spores. These spores are difficult to destroy using
conventional cooking techniques. In fact, nonkilling heat shock and the
lack of preservatives or acidifiers may even enhance germination and
toxin elaboration.

To safely prepare foods for canning or long-term storage, the U.S.
Department of Agriculture recommends that all low-acid foods (i.e.,
foods with a pH \> 4.6, including meats, seafood, poultry, milk, and
fresh vegetables) be sterilized at temperatures of 116 to 121C
(240-250F) in pressure canners operated at 0.66 to 0.97 atm (10-15
lb/in^2^). At these temperatures, the time needed to destroy bacteria in
low-acid canned food ranges from 20-100 minutes. The exact time depends
on the kind of food being canned, the way it is packed, and the amount
of food being cooked.

**REFERENCES**

Villar RG, Shaprio RL, Busto S, et al. Outbreak of Type A botulism among
bus drivers and development of a botulism surveillance and antitoxin
release system in Argentina. JAMA 1999; 281:1334-1340.

Bryan FL, Anderson HW, Cook OD, et al. Procedures to investigate
foodborne illness. International Association of Milk, Food, and
Environmental Sanitarians, Inc.: Ames Iowa; 1987.

Centers for Disease Control and Prevention: Botulism in the United
States, 1899-1996. Handbook for Epidemiologists, Clinicians, and
Laboratory Workers, Atlanta, GA. Centers for Disease Control and
Prevention, 1998.

Shapiro RL, Hatheway C, Becher J, Swerdlow DL. Botulism surveillance and
emergency response. A Public Health Strategy for a Global Challenge.
JAMA 1997; 278:433-435.

Shapiro RL, Hatheway C, Swerdlow DL. Botulism in the United States: A
clinical and epidemiologic review. Annals of Internal Medicine 1998;
129:221-228.

St. Louis ME, Peck SHS, Bowering D, et al. Botulism from chopped garlic:
Delayed recognition of a major outbreak. Annals of Internal Medicine
1988; 108:363-68.

Townes JM. Cieslak PR, Hatheway CL, et a;. An outbreak of Type A
botulism associated with a commercial cheese sauce. Annals of Internal
Medicine 1996;125:558-63.

**APPENDIX 1**

Foods served to bus drivers in home at terminal stop of bus route in the
first week of

January:

Bologna

Hot dogs

Matambre\*

Mate\*\*

Processed ham

Sauce

Salami

Solid ham

\*Matambre is a traditional meat roll in Argentina. At the terminal stop
it was sliced and served in sandwiches, usually with a spicy sauce.

\*\*Mate is green tea.

[^1]: ^\*^ This is not the press release distributed by the Ministry of
    Health but was developed specifically for this exercise.