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Clostridium Perfringens Outbreak at a Workplace Party, Cheat Sheet of Epidemiology

A detailed case study of a gastrointestinal illness outbreak that occurred at a workplace holiday party. The investigation, conducted by the rockaway township division of health, involved a thorough epidemiologic analysis, including interviews with attendees, food histories, and laboratory testing. The study identified clostridium perfringens as the causative pathogen, highlighting the importance of proper food handling practices, particularly for potentially hazardous foods. Valuable insights into outbreak investigation methodologies, food safety protocols, and the role of public health agencies in preventing and controlling foodborne illnesses.

Typology: Cheat Sheet

2023/2024

Uploaded on 10/24/2024

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INTRODUCTION
At 6:16am on December 17, the Health Officer received a text message from an employee,
advising that he had been up much of the night with abdominal cramps and diarrhea. A second
employee, who participated in the same text exchange, advised at 6:18am that he, too, had
been up most of the night with identical symptoms. At approximately 7:00am, a third employee
also advised that she was up during the night with the same symptoms. All three employees
confirmed that they would not report to work. While commuting to work at 7:05am, the Health
Officer called the certified public health laboratory with which the Rockaway Township Division
of Health maintains a contract, and arranged for an afternoon pickup of food samples for
microbiological analysis. The Health Officer arrived at work at approximately 7:30am and
immediately launched an epidemiologic investigation.
BACKGROUND
The Rockaway Township administrative workforce held a holiday lunch party at the Rockaway
Township Municipal Building on Wednesday, December 16. The party lasted from
approximately 11:45am through 2:00pm, and food was prepared for display/service before
11:45am. Several foods were purchased at a local Costco store, other foods were catered by
Joey’s Jubilations in Boonton Township, and two food items were home-prepared by
employees. In addition, bagels and spreads were purchased from Bagelicious, Rockaway
Borough, for service between 8:30am and 11:00am.
The party was attended by about 50 people, 47 of whom were interviewed. Of those who ate,
31 (66%) became ill and were defined as cases. Food items served at the buffet lunch included
meatballs, chicken wings, chicken Francese, sausage and peppers, shrimp, penne pasta, fresh
mozzarella and tomatoes, spinach dip, salad, cheese/pepperoni platter, fresh fruit and other
items.
METHODS
Epidemiologic Investigation
A. Case Definition: A case was defined as any person experiencing diarrhea and/or
abdominal cramps within 20 hours after eating at the December 17, 2015 holiday party.
B. Case Ascertainment
A list including each party attendee and contact information was obtained from
administrative staff. Forty-seven (47) individuals were interviewed by December 19, 2015.
C. Survey
Each party attendee was interviewed either in person or via telephone, and the
following information was ascertained:
Age and gender
Symptoms of illness
Date and time of onset
Duration of illness
Food items consumed
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INTRODUCTION

At 6:16am on December 17, the Health Officer received a text message from an employee,

advising that he had been up much of the night with abdominal cramps and diarrhea. A second

employee, who participated in the same text exchange, advised at 6:18am that he, too, had

been up most of the night with identical symptoms. At approximately 7:00am, a third employee

also advised that she was up during the night with the same symptoms. All three employees

confirmed that they would not report to work. While commuting to work at 7:05am, the Health

Officer called the certified public health laboratory with which the Rockaway Township Division

of Health maintains a contract, and arranged for an afternoon pickup of food samples for

microbiological analysis. The Health Officer arrived at work at approximately 7:30am and

immediately launched an epidemiologic investigation.

BACKGROUND

The Rockaway Township administrative workforce held a holiday lunch party at the Rockaway

Township Municipal Building on Wednesday, December 16. The party lasted from

approximately 11:45am through 2:00pm, and food was prepared for display/service before

11:45am. Several foods were purchased at a local Costco store, other foods were catered by

Joey’s Jubilations in Boonton Township, and two food items were home-prepared by

employees. In addition, bagels and spreads were purchased from Bagelicious, Rockaway

Borough, for service between 8:30am and 11:00am.

The party was attended by about 50 people, 47 of whom were interviewed. Of those who ate,

31 (66%) became ill and were defined as cases. Food items served at the buffet lunch included

meatballs, chicken wings, chicken Francese, sausage and peppers, shrimp, penne pasta, fresh

mozzarella and tomatoes, spinach dip, salad, cheese/pepperoni platter, fresh fruit and other

items.

METHODS

Epidemiologic Investigation

A. Case Definition: A case was defined as any person experiencing diarrhea and/or

abdominal cramps within 20 hours after eating at the December 17, 2015 holiday party.

B. Case Ascertainment

A list including each party attendee and contact information was obtained from

administrative staff. Forty-seven (47) individuals were interviewed by December 19, 2015.

C. Survey

Each party attendee was interviewed either in person or via telephone, and the

following information was ascertained:

• Age and gender

• Symptoms of illness

• Date and time of onset

• Duration of illness

• Food items consumed

D. Analysis

Attack rate and relative risk were calculated for each food item served and statistical

significance was tested using chi-square or Fisher’s exact test as indicated. A p-value

<0.5 was considered significant. Small sample size provided for wide confidence

intervals in assessing statistical significance.

Table 1: Symptoms Reported by Cases

Symptom # Reporting Symptom (N = 31)

Diarrhea 31 (100%)

Abdominal Pain 26 (84%)

Chills 12 (39%)

Nausea 11 (35%)

Headache 5 (16%)

Muscle Ache 4 (13%)

Vomiting 2 (6%)

Fever 0 (0%)

Human Microbiology

The public health investigation team spoke to each ill person on the morning of Thursday,

December 16, and requested/recommended that each sick individual visit with their personal

physician and ask that a stool specimen be collected. Despite the Division of Health’s request,

no specimens were submitted/obtained and no pathogen was clinically isolated.

Environmental Investigation

The Health Officer and two Registered Environmental Health Specialists conducted an environmental

investigation by inspecting the premises of the event and interviewing the party coordinators upon initial

notification of illnesses. It was reported by several individuals that a meatball dish, which was to be held

and served hot, was served cold to lukewarm. It was further reported that someone had turned off the

power to the crockpot in which the meatballs were to be reheated and stored/displayed. Upon

examination of two leftover meatballs, the internal color appeared slightly pink, though there was no

evidence to confirm that the meatballs were not cooked adequately when initially prepared at home.

Based on symptoms, incubation periods, foods served and food handling practices ascertained

during interviews, 15 foods were packaged, tagged and provided with chains of custody by the

Registered Environmental Health Specialists and Health Officer. The food specimens were picked up

at approximately 1:00pm on Friday, December 17 by the health department’s contractual certified

public health laboratory. All food samples were tested for general E. coli, B. cereus, C. perfringens,

and some for Salmonella and Staphylococcus Aureus. The meatballs were also tested for E. coli

Sausage & Peppers 18 6 24 75% 13 10 23 56.5% 1. Chicken Francese 25 5 30 83% 6 11 17 35% 2. Penne Pasta 21 5 26 80% 10 10 20 50% 0. Salad 15 10 25 60% 16 6 22 72.7% 0. Pepperoni & Cheese 10 1 11 90% 21 15 36 58% 1. String Beans 18 3 21 85. %

Mozzarella & Tomatoes 15 8 23 65% 18 8 26 69% 0. Spinach & Artichoke Dip 9 4 13 69% 20 9 29 68.9% 1. Bagels 17 9 26 65% 14 7 21 66% 0. Cream Cheese 12 5 17 70% 19 12 31 61% 1. Butter 6 6 12 50% 23 9 32 71.8% 0. Olive Platter 6 2 8 75% 20 6 26 76.9 0. Strawberries & Grapes 13 7 20 65% 18 9 27 66% 0. Caramel Cake 5 1 6 83% 21 7 28 75% 1. Almond Cake 12 2 14 85. %

Apple Pie 2 0 2 100% 8 0 8 100% 1 Chocolate Cake 6 4 10 60% 20 5 25 80% 2. Assorted Cookies 15 10 25 60% 16 6 22 72% 0.

DISCUSSION

The epidemic curve suggests a common/point source outbreak. The epidemiologic evidence

points to several possible sources, including the chicken wings (RR = 1.74, p = .01), chicken

Francese (RR = 2.36, p <.001), string beans (RR = 1.86, p <.01) and penne pasta (RR = 1.62,

p<.03), but the most significant relative risk and p value was associated with a homemade

meatball dish (RR = 3.48, p = .00002).

Epidemiologic evidence therefore strongly suggests that the meatballs were the vehicle of

infection. In addition, very high levels of Clostridium perfringens were found in samples of the

meatballs, which were submitted to a certified public health laboratory for analysis. Several

individuals reported that the meatball dish was served cold to lukewarm, with the meatballs

reportedly held at room temperature for several hours prior to consumption, and this could

explain pathogen growth. The symptoms, incubation periods, ingredients and food handling

practices all support the presence and growth of C. perfringens.

CONTROL MEASURES

1. All employees contacted via phone with symptoms meeting the case definition were

excluded from work. Those meeting the case definition who appeared for work were

sent home and advised not to report to work until they were free of symptoms.

2. All holiday party attendees with symptoms meeting the case definition were advised to

consider seeing their primary care physician, and to request that a stool sample be

obtained.

3. All holiday party foods that were not submitted for laboratory analysis were discarded.

4. The entire area used for the holiday party was cleaned thoroughly by staff.

5. Proper food preparation, heating, cooling, reheating and hot-holding practices were

reviewed with appropriate party attendees. Emphasis was placed on the sensitivities

and risks involving homemade potentially hazardous foods served for group

consumption.

OUTCOME

No additional cases of gastrointestinal illness were reported to the local health department

after December 17.

SUMMARY

An outbreak of gastrointestinal illness occurred among a group of employees attending a

workplace holiday party. Based on laboratory data, symptoms, food handling practices and

incubation periods ascertained during interviews, Clostridium perfringens was implicated as the

causative pathogen. C. perfringens was isolated from food samples of a meatball dish, and party

attendees noted that the meatballs were not adequately heated when served/consumed.