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Outbreak Investigation

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OUTBREAK INVESTIGATION

Abstract

This report is based on a suspected case of Salmonella at Flinn Corporation after a

particular nurse noted that more employees get sick. In line with the CDC outbreak investigation

steps, interviews, an epidemic curve, and a retrospective cohort study are used in this study to

confirm the outbreak and identify its source. The methods employed in the analysis are statistical

and epidemiological to measure the frequency of diseases, signs, and causal objects that include

foods consumed in the corporate cafeteria. The results imply a point-source exposure with a

high-risk ratio associated with a particular food item. The measures which are given to avoid

similar circumstances in the future are improved measures of handling foods and training of all

personnel, as well as regular health and safety inspections. This study also calls for an efficient,

evidence-based response approach in corporations to reduce exposure risks and future

pandemics.
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Introduction

When many of the employees caught the flu, Flinn Corporation became concerned about

an epidemic, and a registered nurse currently working for the company had to go through the

process of interviewing employees and collecting samples. Having a suspicion of Salmonella as

the causative agent, the nurse enlisted the services of local epidemiological assistance. The food-

borne pathogen, Salmonella, is well associated with gastroenteritis symptoms, including fever,

diarrhea, and abdominal pain, as well as serious health complications in the absence of effective

control measures. Due to the contagious nature of the flu and other diseases that circulate in large

organizations where many people gather and often eat in the same canteens, it is essential to

establish the existence of the flu and determine its cause for remedial measures to be taken. This

report uses the CDC outbreak investigation process, examines factors, and analyzes patterns of

the disease occurrence in order to establish the presence of an outbreak and make

recommendations to protect the health of employees at Flinn Corporation.

Establishing the Outbreak

From the completed “Nurse’s Interview” sheet, it can be concluded that there are grounds

to assume that Flinn Corporation’s employees are affected by Salmonella. The nurse gathered

data in relation to the age, sex, any signs or symptoms experienced within the last two weeks,

and whether the employee had taken food in the cafeteria at the workplace before developing the

symptoms. Of the 20 employees reported, 12 employees had gastrointestinal-related illnesses,

fever being the most frequent symptom at 58.3% of the ill employees, diarrhea at 83.3%, and

abdominal cramps at 50%. The onset of the symptoms in the identified individuals is closely

clustered, with the onset of the first symptom in one of the affected persons reported to have

been on the 1st of February 2018, while the last symptom was reported on the 5th of February
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2018. The concentration of the onset date of the illness also enhances the possibility of the

outbreak coming from a single source when the onset is clustered within a few days. In addition,

among the twelve symptomatic employees, ten had dined at the corporate cafeteria, which

suggests that the likely etiology could have been associated with cafeteria food.

Breaking down the results according to individual symptoms reveals trends

corresponding to a Salmonella outbreak. For example, some of the signs that the affected

employees display are abdominal pain, fever, chills, and diarrhea, which are all consistent with

Salmonella (Krishnasamy et al., 2020). For instance, John, who ate at the cafeteria, and Sean had

many symptoms, like fever, chills, and diarrhea. Another diner from the cafeteria, Catherine,

complained of fever, abdominal cramps, diarrhea, and blood in stool, a condition that is

sometimes believed to have been caused by Salmonella. The similarities in symptom patterns

and the time interval between cases seen in cafeteria-goers indicate that the group has had a point

source exposure to tainted food, which could have propagated illness in the group.

The grouping of cases, the similar time that symptoms developed, and the index exposure

to the cafeteria all point to the need for more investigation into the possibility that the cafeteria is

the source of the outbreak. It becomes important to establish this as an outbreak because it

enables the corporation to implement prevention measures, such as examining the practices it has

on food handling and hygiene with a view to preventing the spread of the sickness. Determining

the specific food type involved will aid in the prevention of further occurrences and probable risk

reduction.

Verifying Diagnosis
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Salmonellosis, an infection caused by Salmonella bacteria, is a common foodborne

illness that typically manifests as gastroenteritis. As stated by the CDC, foods that are most

commonly linked to Salmonella are meats, poultry, eggs, dairy products, and fresh fruits and

vegetables. The signs of salmonellosis occur between 6 and 72 hours after consuming

contaminated food or water and manifest themselves in diarrhea, stomach cramps, fever, nausea,

and vomiting, which lasts for 4-7 days (CDC, 2024). The worst effects can lead to dehydration,

most commonly in groups who are most at risk, including children, the elderly, and

immunocompromised individuals (Popa & Papa, 2021). Although less common, complications

can include bacteremia, where the bacteria spread into the bloodstream, leading to potentially

life-threatening conditions if untreated (Dyda et al., 2020).

The chain of infection for salmonellosis involves several vital stages: the pathogen

(Salmonella bacteria), the source or reservoir (frequently animals or food products), and how the

pathogen got to the susceptible host and the host. The bacteria that cause salmonellosis mainly

inhabit the gastrointestinal tracts of animals and can infect foods during processing (Canning et

al., 2023). The mode of transmission involves the spread through the fecal-oral route, which may

be done by taking contaminated food products or drinking water. In this case, the corporate

cafeteria likely serves as the source, where improper food handling practices may have

introduced the bacteria into the food consumed by employees. Once ingested, Salmonella

bacteria pass through the stomach to the intestines, where they can multiply, causing infection

and associated gastrointestinal symptoms. The spread of infection can be minimized by

controlling each link in the chain, mainly through safe food handling and personal hygiene

practices to reduce contamination risk (Lund et al., 2022). From among the ill employees,

symptoms such as diarrhea, fever, stomach cramps, and nausea manifesting the known signs of
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salmonellosis support the possibility that Salmonella is responsible for the outbreak (Latash,

2020). Further testing is necessary to confirm the diagnosis, yet the alignment of symptoms,

combined with likely exposure at a single food source, suggests a strong probability of

Salmonella infection.

Working Case Definition

To best characterize the outbreak, one has to ascertain what portion of infected employees

display each particular sign. “In this step, one has to examine the symptoms as they relate to the

12 employees of the Flinn Corporation and the percentage distribution of each symptom. A

review of each symptom and the proportion of employees’ sicknesses is as follows.

Table 1: Symptoms and Affected Employees with Percentages

Corresponding

Number of Percentage of Ill

Symptoms Code Employees Employees

Nausea N 3 25.00%

Vomiting V 3 25.00%

Abdominal cramps Ac 6 50.00%

Diarrhea D 8 66.67%

Fever F 8 66.67%

Chills C 8 66.67%

Headache H 8 66.67%

Blood in the stool Bs 1 8.33%

Total Number of Ill Employees 12

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These percentages indicate the probability of any of the symptoms of the disease to

develop in the employees they infected as their risk factors. These observable signs observed on

the employees of Flinn Corporation resemble signs of salmonellosis. Therefore, table 1 depicts

how each of the individuals was affected by different symptoms of Salmonella bacteria.

Descriptive Epidemiology
Descriptive epidemiology is also valuable for practical work since it can operationalize

epidemiological data comparatively quickly, making it possible to define the characteristics of

the affected population that are necessary to build. This step is vital in identifying trends and

risk-easing factors and the likely source of the upcoming outbreak (Popa & Papa, 2021). Thus,

the analysis will focus on three key components: person, place, and time.

Person

Table 2: Gender Distribution

Category Number of Percentage
Employees

Ill Male Employees 7 58.33%

Ill Female Employees 5 41.67%

Total Employees 12 100%

Mean Age

Table 3: Mean Age of Ill Employees

Name Age

John 55

Nancy 38

Kate 32

William 25
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Catherine 36

Sean 31

Rodney 41

Graham 60

Peter 33

Chelsea 45

Joan 44

Colleen 48

Average 40.67

Age

Table 2 shows the percentage of male and female workers to show the differences by

gender of the affected employees. The number of infected employees, which is found in Table 3,

offers a clue about the effect of the outbreak on employees according to their age since the table

contains the average age of the sick employees. The study revealed that the employees' illnesses

are mostly male employees whose ages are, on average, 40.67. Therefore, the data analysis is

helpful in identifying the population likely to be impacted or at risk of the outbreak.

Place

Table 4: Ill Employees Who Ate at the Cafeteria

Number of Employees 11

Total number of ill employees 12

Percentage of ill employees at the cafeteria 91.67%

Table 5: Healthy Employees Who Ate at the Cafeteria

Number of Employees 1
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Total number of healthy employees 8

Percentage of employees at the cafeteria 12.50%

The study found that the Flinn Corporation’s cafeteria was a source of the infection.

Therefore, the hypothesis is confirmed by performing data analysis, as shown in Tables 4

and 5. As per the survey, 91.67% of people suffering from that disease used the cafeteria facility,

in comparison to the 12.50% of employees who did not have any disease. Accordingly, this

evidence is consistent with the hypothesis that the cafeteria is the cause of the illness spread.

Time
Epidemic Curve

Epidemic Curve of Salmonellosis Outbreak Cases at Flinn

Corporation
3.5

2.5

1.5

0.5

0
29-Jan 30-Jan 31-Jan 1-Feb 2-Feb 3-Feb 4-Feb 5-Feb 6-Feb 7-Feb

The epidemic curve presented here shows that it is a point-source epidemic. Such a curve

is described as rapid ascendance with a slow descent within a unique incubation period (CDC,

2024). Hence, this distribution suggests that people most probably acquired the infection from a

common source at the same time.

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Hypothesis testing in a retrospective cohort study

Since the study is a retrospective cohort study, one is in a position to establish a

relationship between the cafeteria food items served and the outbreak. To achieve this test, the

risk ratio and attack rates of the foods that employees take at the cafeteria are determined. The

attack rates are helpful in quantifying the number of people who had their meal at the cafeteria

and took a particular food product (Tan et al., 2022). Therefore, the risk ratio measures the

probability of contracting the illness of those who consumed the particular food product against

those who did not.

a. Attack Rates

b. Risk ratio

Results from the Retrospective Cohort Study

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Table 6: Attack Rate and Risk Ratio Calculation

Analysis of Each Food Risk Ratio

Based on the present study findings, it was established that a higher number of people

who had consumed baked chicken contracted the illness, thus having a 4.14 relative risk of

contracting the illness compared to people who did not consume the food product. This suggests

a significant likelihood connected with baked chicken consumption regarding the outbreak (Tan

et al., 2022). Further, the study showed that persons who used mashed potatoes exposed

themselves to a 1.64-fold increased risk of illness in comparison to their counterparts who

shunned it but presented a lower risk than baked chicken. The spinach consumers had 1.29 times

the probability of getting sick; therefore, the association with the disease was relatively low. In

this study, a risk ratio of 1.15 was also observed for the fruit salad, which is most probably owing

to the natural sugars in fruits; thus, the association with the illness is negligible.
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This, coupled with a reasonably acceptable risk ratio of 1.00, implies that there is no

difference in the epidemiology of the chosen illness between consumers and non-consumers of

chocolate ice cream. They went to self-suspicion, and this food cannot cause the disease. The

foods have a 0.82 risk ratio, which means that consuming the foods has a smaller risk of getting

ill than not consuming them. It is, perhaps, unlikely that any of these foods played a role in the

outbreak. Moreover, this analysis revealed that the relative risk of all items ranging from water,

milk, vanilla ice cream, and cake to coffee was 0.27 to 0.75. Therefore, these foods could not

readily infect people and may not either cause or prevent the disease.

Prevention and Control Measures in the Cafeteria

The findings of the retrospective cohort study show that the baked chicken bought from

the cafeteria in Flinn Corporation most probably caused the spread of Salmonella. With the

attack rate and risk ratio this high, it was probably the baked chicken salad that caused the high

rate of sickness among the employees. Therefore, in order to avoid similar occurrences and

protect the foods that are offered in the cafeteria, the following prevention and control measures

considering the principles of the well-organized food safety regime should be used in the future.

Remove Hazardous Food

One rule is to ensure the cafeteria restocks baked chicken as soon as possible while other

food items that present similar symptoms must be removed, and all unsalted parts must be

discarded as well. Thus, if the specific supplier is the source of the contamination of a particular

ingredient in a flavored food, it is necessary to let them know so that they can help pull out the

toxic food from the market for the welfare of the people. Hence, the need to influence the staff to
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wash and disinfect all the food preparation and handling tools that are in contact with poisonous

food.

The Implementation of Food Handling and Preparation Protocols

It is recommended that the cafeteria should adopt practices on food handling and

preparation such as the Hazard Analysis Critical Control Points (HACCP). The HACCP protocol

indicates that many administrative controls should be followed within a food business when

handling and preparing food. The managers and the other staff members check and guarantee

that goods such as eggs, poultry, and prepared salads get to the required internal temperature to

neutralize all the dangerous bacteria. Heat kills germs, and therefore, one could serve hot foods at

140 F or 60 C and avoid serving cold foods at above 40 F or four °C (CDC, 2024). Thus, to help

eliminate the risks of bacterial contamination, it is imperative to handle food properly.

Food Safety Training and Orientation

Before serving food, all cafeteria workers are instructed to take food safety training,

which includes best practices regarding food handling, cooking, and storage. Some of the

training topics should include cross-contamination, temperature control, proper cleaning and

sanitation of tools, trolleys, and other utensils, and other relevant prohibited practices. Measures

of Hygiene in food include hand hygiene, appropriate dress code, and the use of gloves when

handling food (Wessels & Gouws, 2021). Further, infection control measures require employees

to undergo screening for the existence of food-borne pathogens among employees.

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Inspections and Monitoring of Food Storage

Another critical factor is the need for regular inspections and monitoring to ensure that

high standards of food hygiene are maintained. This involves timely monitoring of the

temperatures in food storage areas, monitoring cleanliness and cross-contamination hazards

within storage and preparation areas, and managing the sanitation arrangements for common

cafeteria areas (Wessels & Gouws, 2021).” Moreover, routine microbiological examination of

foods, especially the crops popular with outbreaks like salads and RTE items, underlines these

dangers and, in advance, decreases their likelihood and effects.

Quality of Food Supplied

In the food supply system, there is a necessity for the betterment of supply chain

management where high-risk foods such as eggs, dairy, fruits, and vegetables need attention for

proper safety. This may involve checking the authenticity of suppliers, asking for evidence of

safe preparation, and purchasing from suppliers who ensure safe methods (CDC, 2024). Also,

systems for traceability are crucial since firms can detect which batch was affected to form

contingency plans to contain the spread of the illness through the removal of the offending items

from circulation.

Reporting to Authorities

This collaboration aspect is also very crucial in reporting procedures in matters

concerning public health. If the investigation is still underway, report the outbreak to the local

public health department; where the report is available, the department can give further

assistance, pamphlets, and details of how to combat the epidemic or to avoid its recurrence
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(Wessels & Gouws, 2021). Therefore, examining and analyzing cafeteria food safety procedures

and policies regarding the outcomes that come from the occurrence discussed above and

advancement in food safety research will help enhance the cumulative process of avoiding food-

borne diseases.

Conclusion

The findings suggest that Flinn Corporation had an actual epidemic break out, as 60% of

the workers got sick from suspected salmonellosis. The clinical manifestations that the affected

workers developed, including abdominal pain, diarrhea, and fever, are typical of salmonellosis.

Descriptive epidemiology supported by results of retrospective cohort analysis indicates that

cafeteria food items were the source of the outbreak. The following measures to reduce the risk

of contamination and improve the nursery's food safety must be implemented: the company has

to ensure very high standards of hygiene are adopted by the people that handle foods, such as

through frequent washing of hands and other requirements in the preparation process. For safety

to be enhanced, there is a need to check the temperature of the foods stored quite often. The

cafeteria staff needs to be trained on the guidelines of food safety. In addition, the action plan for

the essential actions should include inspections that should be carried out from time to time to

check on the implementation of food safety adoptions. Therefore, if Flinn Corporation

implements these preventive measures, it can prevent further occurrences, demonstrating care for

employees’ wellbeing.
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References

Canning, M., Birhane, M. G., Dewey-Mattia, D., Lawinger, H., Cote, A., Gieraltowski, L., ... &

Marshall, K. E. (2023). Salmonella outbreaks linked to beef, United States, 2012

2019. Journal of food protection, 86(5), 100071.

Dyda, A., Nguyen, P. Y., Chughtai, A. A., & MacIntyre, C. R. (2020). Changing epidemiology

of Salmonella outbreaks associated with cucumbers and other fruits and

vegetables. Global Biosecurity, p. 2.

Popa, G. L., & Papa, M. I. (2021). Salmonella spp. Infection-a continuous threat

worldwide. Germs, 11(1), 88. https://doi.org/10.18683/germs.2021.1244

Krishnasamy, V. P., Marshall, K., Dewey-Mattia, D., & Wise, M. (2020). Outbreak

characteristics and epidemic curves for multistate outbreaks of Salmonella infections

associated with produce: United States, 2009–2015. Foodborne pathogens and

disease, 17(1), 15–22.https://doi.org/10.1089/fpd.2019.2711

Latash, J. (2020). Salmonellosis outbreak detected by automated spatiotemporal analysis—New

York City, May–June 2019. MMWR. Morbidity and Mortality Weekly Report, p. 69.

https://doi.org/10.15585/mmwr.mm6926a2

Lund, S., Tahir, M., Vohra, L. I., Hamdana, A. H., & Ahmad, S. (2022). Outbreak of

monophasic Salmonella Typhimurium Sequence Type 34 linked to chocolate

products. Annals of Medicine and Surgery, 82.

https://doi.org/10.1016/j.amsu.2022.104597

Tan, S. J., Nordin, S., Esah, E. M., & Tan, S. J., Nordin, S., Esah, E. M., & Mahror, N. (2022).

Salmonella spp. in chicken: prevalence, antimicrobial resistance, and detection

methods. Microbiology Research, 13(4), 691-705.

https://doi.org/10.3390/microbiolres13040050
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Wessels, K., Rip, D., & Gouws, P. (2021). Salmonella in chicken meat: Consumption, outbreaks,

characteristics, current control methods and the potential of bacteriophage

use. Foods, 10(8), 1742. https://doi.org/10.3390/foods1008174

CDC. (2024, May 13). Introduction to epidemiology. Public Health 101 Series.

https://www.cdc.gov/training-publichealth101/php/training/introduction-to-

epidemiology.html

CDC. (2024, June 20). Steps in a Multistate foodborne outbreak investigation. Foodborne

outbreaks. https://www.cdc.gov/foodborne-outbreaks/investigation-steps/index.html