Oswego Outbreak

Oswego Outbreak Case Study

Read the “Oswego Outbreak Investigation” located in the Topic Materials.

Part 1

Complete the following:

Using the line listing in the Excel “Oswego Line Listing Workbook,” calculate the attack rate ratios for each food item using the table in the Excel “Oswego Attack Rate Table.” Create a separate 2×2 table for the food item you think is responsible for the outbreak and interpret the attack rate ratio for this food item. Refer to the “Creating a 2×2 Contingency Table” resource for guidance.

Using the line listing in Excel “Oswego Line Listing Workbook,” construct an epidemic curve by the time of onset of illness. What does this curve tell you regarding the average incubation period, source, and transmission?

Using the incubation range and clinical symptoms, identify potential infectious agents that could be responsible for the outbreak (refer to the Topic Material, “Compendium of Acute Foodborne and Waterborne Diseases”). Discuss your rationale.

Part 2

In a 500-750 word paper, evaluate the situation and present your findings. Including the following:

Does this case meet the definition of an “outbreak?” Why or why not?

Identify the steps required to investigate an outbreak. How did these steps help in investigating the Oswego event? Include the relevant information needed for each step to be successful.

Discuss the possible routes of transmission for the expected agent.

Based on this information, what control measures would you recommend? State whether they are primary, secondary, or tertiary prevention strategies.

Prepare this assignment according to the guidelines found in the APA Style Guide, located in the Student Success Center. An abstract is not required.

Oswego Case Study

2*2 Contingency Table for Vanilla Ice Creme

 Sick (Ill)Not Sick (Ill)Total
Food Exposure431154
No Exposure31821

The highest attack rate ratio for the food taken is the vanilla ice creme, which was at 5.71%, hence making it the culpable contaminated food. Moreover, it should be investigated for contaminants. A total of 54 people ate the vanilla ice creme with 43 of them falling ill while 11 did not have acute gastroenteritis. Moreover, three people did not partake of the vanilla ice creme but fell ill while 18 did not take it and were not sick. As such thee total number of people investigated from the supper in Oswego county was 75 with all of them having eaten at the party with 46 of them (61.33%) of them falling ill while 29 (38.67%) not falling sick. A small number of the attendees (3) ate the vanilla ice creme but did not exhibit signs of acute gastroenteritis.

Epidemic Curve

The epidemic curve described as a graphical representation of the time of taking the suspected contaminated vanilla ice creme and the time that the clinical signs and symptoms of acute gastroenteritis. Additionally, it also provides information on the outliers, which are the earliest case reported after ingestion and the last case to be reported. The magnitude and pattern of the spread of the outbreak can be detonated from the graphs. The following graph shows the range of incubation and the number of cases reported in the duration.

Range/Incubation Duration Table

IDTime of MealTime of OnsetRange/ Incubation duration
28:00 PM12:30 AM4.5
36:30 PM12:30 AM6
46:30 PM12:30 AM6
67:30 PM10:30 PM3
77:30 PM10:30 PM3
87:30 PM2:00 AM6.5
910:00 PM1:00 AM3
107:00 PM11:00 PM4
147:30 PM2:00 AM6.5
2110:00 PM1:00 AM3
2710:00 PM1:00 AM3
3210:00 PM1:00 AM3
3310:00 PM1:00 AM3
3910:00 PM1:00 AM3
487:00 PM1:00 AM6
5211:00 AM3:00 PM4
5810:00 PM1:00 AM3
597:30 PM2:30 AM7
607:30 PM11:30 PM4
6510:00 PM1:00 AM3
717:30 PM1:00 AM5.5
727:30 PM12:00 AM4.5

Epidemic Curve Oswego Outbreak

Staphylococcal Food Contamination

The incubation period and the clinical sign exhibited by the attendees of the church in Oswego County resembled that of the staphylococcal contamination in food at its ingestion by the church members. Staphylococcus is a common bacterial and causes food poisoning through the production of toxins, and hence, there is the need to ensure that meals are heated before serving to denature the toxins. The incubation period for the disease is between 30 minutes to 8 hours (Hennekinne, De Buyser, & Dragacei, 2012). In Oswego County, the incubation periods had an outlier at three hours and the other at seven hours with the average range being 4 hours. Moreover, the clinical signs dissipated after 24 hours with no fatality recorded. The suspected foodstuffs that could have been consumed to lead to the infection was vanilla ice creme which has a high content of milk and eggs which could also have been contaminated by staphylococcal species which would, in turn, produce toxins causing gastroenteritis.

Definition of an Outbreak and if it qualifies in Oswego County

An outbreak is defined as the occurrence of an infection, disease, or condition localized at a particular location and time and affect a group of individuals.  Foodborne diseases quality as outbreaks as they increase the number of people affected by an infectious pathogen. In Oswego, the people affected had a meal in a church setup and fell ill after consumption of foods and drinks the previous evening. It led to a high number of reported acute gastroenteritis, which led to an outbreak (Ameli, 2015). Moreover, it qualifies to be an epidemic as the number of cases reported in 24 hours was higher than the expected rate in a given community. Therefore, it is an outbreak of an epidemic in a communal setup with 45 people out of the 80 that attended the supper being infected.

Steps for Investigation of an Outbreak

An outbreak is investigated by an epidemiologist as part of a public health team to determine the origin of an infection in a community, the risk factors, transmission, susceptible persons, and the mitigation factors which are implemented to minimize its spread and the prevention measures aimed at ensuring no new cases are reported (Robinson, Walker, & Pallen, 2013).  The first step in investigating an outbreak is the identification of the existence of an outbreak. The epidemiologist must note the number of cases reported as being abnormally high for the disease at that particular location and time as some diseases may be seasonal with increased incidence rates at specific times or seasons in a year.

Secondly, the public health personnel charges with the investigation verify the diagnosis and formulate a case definition which includes the location and the community affected while mapping out the spread of the disease from information gathered from hospitals, health centers, and other healthcare facilities (Kearney, 2018). Thirdly, he develops a hypothesis which will be used to drive the investigation of the case to assess and define the cause and transmission of the condition. Once the data is analyzed, the hypothesis is improved to expound on the data and scope of the study (Giesecke, 2014). Forth, the epidemiologist uses assessment results to develop the prevention and intervention strategies which are implemented in the community and then evaluated for effectiveness and then released to the rest of society to protect them from the infection outbreak.

Possible Routes

In Oswego County, the possible route for the outbreak was through ingestion of the pathogens. The sick individuals ate supper in church and complained of acute gastroenteritis. Hence the main route of transmission was through ingestion of contaminated foodstuffs (Kearney, 2018). Moreover, there was a small number that did not report to the health facility, which meant that they probably did not ingest the specific foodstuff, which was the culprit in the spread of the infectious agent. Furthermore, there was a need to collect samples of the leftovers for analysis to verify the specific foodstuff eaten.

Moreover, the samples collected from the affected individuals upon laboratory analysis will reveal the type of pathogen, and therefore the definitive diagnosis of the outbreak will be revealed, As such the epidemiologist through the case, definition and plan will be in a position to implement preventative and mitigation measures in the community (Kearney, 2018). Additionally, the source of the contaminated food is important as it ensures that the elimination of the risk factors protects the rest of society in a designated location. Consequently, determining the route of transmission aids in the execution of effective mitigations factors.

Control Measures and Recommendations

An epidemiologist investigating a case study in a community is charged with the responsibility of making recommendations and implementing mitigation factors based on their findings and results. In Oswego County, the source of the enteritis was a foodborne contagion due to the ingestion of contaminated food. The main transmission route was through infected person’s contact with foodstuffs and hence there is need to ensure that the individuals who are infected do not handle food even during the latent phase of the infection after treatment (Jackson & Meah, 2018). Ultimately, it would minimize the risk of transmission of the infection to the healthy population in the community and institute as a primary prevention strategy. Moreover, there should be through cleaning of the foodstuff for preparation and ensuring that it is handled in hygienic condition. The kitchen should be clean with protective clothing worn by the handlers to minimize contact with the already cleaned food.

Additionally, everyone in the community should be encouraged to wash their hands after visiting the lavatories with soap and disinfect their hands before handling any food. The eateries and other food service centers should be disinfected to reduce the pathogen load and hence prevent its spreads in the community as a secondary prevention intervention (Cody & Stretch, 2014). Health facilities should also be prepared with an adequate supply of rehydration fluids and medication. There should be isolation wards to prevent the spread of contagion in the institutions where the infected are admitted for treatment and rehydration therapy and observation as the tertiary prevention measures. Consequently, it will provide adequate safety measures for other patients in the facilities as they are already vulnerable due to immunosuppression.


Ameli, J. (2015). Communicable diseases and outbreak control. Turkish Journal of Emergency Medicine, 15(suppl 1), 20-26. doi:10.5505/1304.7361.2015.19970

Cody, M. M., & Stretch, T. (2014). Position of the academy of nutrition and Dietetics: Food and water safety. Journal of the Academy of Nutrition and Dietetics, 114(11), 1819-1829. doi:10.1016/j.jand.2014.08.023

Giesecke, J. (2014). Primary and index cases. The Lancet, 384(9959), P2024.

Hennekinne, J.-A., De Buyser, M.-L., & Dragacei, S. (2012). Staphylococcus aureus and its food poisoning toxins: Characterization and outbreak investigation. FEMS Microbiology Reviews, 36(4), 815-836.

Jackson, P., & Meah, A. (2018). Re-assessing vulnerability to foodborne illness: Pathways and practices. Critical Public Health, 28(1), 81-93.

Kearney, G. D. (2018). Introduction to foodborne illness outbreak investigations. In Environmental Public Health: The Practitioner’s Guide (pp. 315-355). APHA Press.

Robinson, E. R., Walker, T. M., & Pallen, M. J. (2013). Genomics and outbreak investigation: From sequence to consequence. Genome Medicine, 5(4), 36.