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, MD1

1Centers for Disease Control and Prevention, 2Ministero de Salud-Region V, 3Ministero de

Salud y Accion Social, 4Pan American Health Organization, 5Departamento de Bacteriologia,

Instituto Nacional de Enfermedades Infecciosas, 6Hospital F. J. Muñiz, Buenos Aires, Argentina

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

NOTE: This case study is base d on a rea l-life outbrea k investigatio n underta ken 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 tha n 3 hours. 

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

approac h to foodborne disea se outbrea k investigatio n. Procedu res and po licies in

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

outbreak to outbreak.

It is anticipate d that the ep idemiolo gist investiga ting a foodb orne disea se outbrea k will

work within the framework of a n “investig ation team” which inclu des perso ns 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 investiga tions are successfully com pleted. 

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

http://www.phppo.cdc.gov/phtn/casestud . . Please inc ies lude 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 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: 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. 
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Instructo r’s version - p. 2

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: 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)

• talk with patients to identify common meals/foods and other persons who may have

shared in them

• 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

• talk with co-workers who may have shared meals with the cases and ask if any have

signs/symptoms of botulism

• 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

• 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
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Instructo r’s version - p. 3

• 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 

• 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. botulinum from gastric aspirate or stool) (NOTE: Few

laboratories do testing for botulism; therefore, this may be an unlikely source for

identifying cases.)

• 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: 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:

• 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)

• the need to identify additional cases so that the individuals can be adequately treated

• 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

• signs and symptoms of botulism and the most likely sources of intoxication
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Instructo r’s version - p. 4

*

This is not the p ress release distributed by the Min istry of Health but was developed spe cifically for this 

 exercise.

• a contact name (and telephone number) who can answer questions

• 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: 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: 

• the Minister of Health (and other appropriate supervisors within the Ministry)

• communications/public relations staff at the MOH

• staff at the public health laboratory who may be involved in testing of clinical or food

specimens

• the local health department where the terminal stop of the bus route is located

• management from the bus company

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

• national and international public health authorities and reference laboratories (e.g., the

World Health Organisation [WHO], the Centers for Disease Control and Prevention

[CDC])

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

On January 14, the MOH distributed the following press release:*

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
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Instructo r’s version - p. 5

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 botulinum. 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: 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:

• The press release is relatively long. Deletion of a number of sentences would make it

more readable without interfering with its goals.
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Instructo r’s version - p. 6

• 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. 

• 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.

• The use of medical terminology (e.g., diplopia, ptosis, dysphagia) and jargon will

prevent many readers from understanding the common symptoms of botulism. 

• The press release, if published, could introduce several biases in future studies:

Selection bias:

- 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:

- Persons diagnosed with botulism might be more likely to recall eating the food

items mentioned as sources of botulism in the news release.

• 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.
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Instructo r’s version - p. 7

Question 5: 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 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: 

• the severity of the disease (e.g., E. coli 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)

• 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)

• whether exposure is suspected to still be occurring

• 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. 
Botulism in Argentina

Instructo r’s version - p. 8

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

No. 

Age

(years) Gender

Work

shift

Onset of neurologic symptoms Symptoms

1 42 M* Morning January 6 blurred vision, double vision,

drooping eyelids, upper and lower

extremity weakness, respirato ry

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 ey elids, difficulty

speaking

5 54 M Morning January 5 blurred vision, double vision,

drooping ey elids, difficulty

speaking, resp iratory difficu lty

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, respirato ry

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
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Instructo r’s version - p. 9

Question 6A: 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.

Figure 1. Onset date of neurologic symptoms among patients with botulism in Buenos Aires, Argentina,

January 1998. (N=9)

Question 6B: 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: 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
Botulism in Argentina

Instructor’s version - p. 10

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: 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: 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. 
Botulism in Argentina

Instructor’s version - p. 11

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: What general types of information would you include in the questionnaire?

• Identifying information (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.

• Demographic information (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.

• Clinical information (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.

• Risk factor information (e.g., foods eaten, underlying medical illnesses, routine

medications). This information allows one to explore the source of the outbreak.

• Source of the information (e.g., patient, parent, spouse, physician). This information will

provide some insight into the accuracy of the information obtained.
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Instructor’s version - p. 12

Question 9: 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: 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.)
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Instructor’s version - p. 13

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.
Botulism in Argentina

Instructor’s version - p. 14

Investigators conducted interviews with each of the drivers of the morning shift of the bus route

to complete the questionnaires.

Question 11: 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:

• The wording of each question should be easily understood and free of technical words or

jargon. 

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

• 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.

• 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). 

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

• 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.
Botulism in Argentina

Instructor’s version - p. 15

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 e aten by ill and well bus d rivers at the home at the terminal bus stop, Ja nuary 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

*Matamb re is a traditio nal meat roll in Arge ntina. 

**Mate is green tea.

Question 12: 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
Botulism in Argentina

Instructor’s version - p. 16

relative = attack rate among persons who ate item 

risk attack rate among persons who did not eat the item

 = # of ill persons who ate item/total # of persons who ate item 

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

 = a/(a + b)

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)

O

2 = t(*ad-bc* - t/2)2

 

(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.
Botulism in Argentina

Instructor’s version - p. 17

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

Food item

Ate item Did not eat item

Relative

Risk

p-value

Ill Well Attack

Rate

Ill Well Attack

Rate

Bologna 1 0 100% 8 12 40% 2.5 0.43

Hot dog 1 1 50% 8 11 42% 1.2 1.0

Matambre 9 2 82% 0 10 0% undefined 0.0002

Mate 4 4 50% 5 3 63% 0.8 1.0

Processed Ham 2 3 40% 7 9 44% 0.9 1.0

Sauce 7 2 78% 2 10 17% 4.6 0.009

Salami 1 1 50% 8 11 42% 1.2 1.0

Solid ham 2 3 40% 7 9 44% 0.9 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: 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
Botulism in Argentina

Instructor’s version - p. 18

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.
Botulism in Argentina

Instructor’s version - p. 19

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 contaminated

infected foodhandler

unclean equipment

cross-contamination

contaminated foods eaten

 raw or lightly cooked

inappropriate container for food

unsafe sources

added po isonous ch emicals

natural toxicant

poor dry-storage practices

inadequate cooking

inadequate reheating

inadequate acidification

inadequate refrigeration

improper cooling

inadequate hot-holding

preparation too far in advance

 of serving

use of leftover foods

inadequate acidification

high water content

inadequa te curing salt 

environment that provides

 favorable conditions for

 pathogen (e. g., anaerobic

 packaging)
Botulism in Argentina

Instructor’s version - p. 20

Question 14: 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:

• Describe the matambre (e.g., all raw materials and ingredients used, source of

ingredients, physical and chemical characteristics such as pH, intended use).

• 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).

• 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. 

• 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).

• 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.

• Collect appropriate specimens (e.g., leftover samples of the implicated food, samples of

the ingredients, environmental testing of food preparation surfaces or equipment).

• 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.
Botulism in Argentina

Instructor’s version - p. 21

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: 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, the following factors will put one at higher risk for botulism:

• inadequate cooking

• inadequate reheating

• long storage time between preparation and consumption

• anaerobic packaging

• low acid and high water content
Botulism in Argentina

Instructor’s version - p. 22

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.

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: 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
Botulism in Argentina

Instructor’s version - p. 23

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:

• 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). 

• 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. 

• 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.
Botulism in Argentina

Instructor’s version - p. 24

• 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.
Botulism in Argentina

Instructor’s version - p. 25

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: 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. 
Botulism in Argentina

Instructor’s version - p. 26

Question 18: 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: 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:

• number of cases of botulism

• number of cases of botulism for which a food is implicated

• average number of cases associated with each implicated food item

• number of cases associated with commercially prepared foods

• time from diagnosis to administration of antitoxin

• sequella and complications among cases

• case-fatality rate

• 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)
Botulism in Argentina

Instructor’s version - p. 27

Figure 3. Onset date of symptoms among patients with Botulism in Buenos Aires, Argentina, December

1997 - January 1998. (N=9)
Botulism in Argentina

Instructor’s version - p. 28

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/in2). 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.
Botulism in Argentina

Instructor’s version - p. 29

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.
Botulism in Argentina

Instructor’s version

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 an d served in sandwich es, usually

with a spicy sauce.

**Mate is green tea.