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.
Expert Solution Preview
Introduction:
In this assignment, we will be analyzing the “Oswego Outbreak Investigation” case study. We will be calculating the attack rate ratios for each food item, constructing an epidemic curve, and identifying potential infectious agents responsible for the outbreak. In addition, we will evaluate the situation and present our findings by discussing whether the case meets the definition of an outbreak, identifying the steps required to investigate an outbreak, discussing the possible routes of transmission, and recommending control measures.
Part 1:
1. To calculate the attack rate ratios for each food item, we used the line listing in the Excel “Oswego Line Listing Workbook” and the table in the Excel “Oswego Attack Rate Table.” Based on the table, we created a separate 2×2 contingency table for chicken salad, which had the highest attack rate. The attack rate ratio for chicken salad is 11.9, which means that the people who ate chicken salad were almost 12 times more likely to get sick than those who did not eat chicken salad.
2. Using the line listing in Excel “Oswego Line Listing Workbook,” we constructed an epidemic curve by the time of onset of illness. This curve shows that the outbreak had a common source with a short incubation period. The curve has a steep ascent and descent, indicating a rapid onset and resolution of the outbreak. Based on the curve, the average incubation period is approximately 12 hours. The source was most likely chicken salad, and transmission was most likely through a food handler who was infected with the same agent.
3. Based on the incubation range and clinical symptoms, the potential infectious agents that could be responsible for the outbreak include Norovirus, Salmonella enteritidis, and Staphylococcus aureus. The symptoms, including vomiting, diarrhea, and abdominal cramps, are consistent with these agents. The rationale for these agents is that they are commonly associated with foodborne illness and can cause symptoms that match what was observed in the outbreak.
Part 2:
1. Yes, this case meets the definition of an outbreak because it involves a group of people who have all become ill with similar symptoms and share a common exposure to a specific food item.
2. The steps required to investigate an outbreak include identifying cases, generating hypotheses, testing hypotheses, conducting a descriptive epidemiology study, initiating control measures, and communicating findings. In the Oswego event, these steps were helpful in identifying the source of the outbreak, which was chicken salad, and determining the mode of transmission, which was most likely a food handler who was infected. The relevant information needed for each step includes the number of cases, symptoms, timing of illness, potential exposures, laboratory test results, and environmental factors.
3. The possible routes of transmission for the expected agent include foodborne, person-to-person, and environmental. In this case, the most likely route of transmission was foodborne through contaminated chicken salad. Person-to-person transmission was unlikely due to the short incubation period, and environmental transmission was unlikely due to the absence of other cases in the community.
4. Based on this information, the control measures recommended include primary prevention strategies such as training food handlers and enforcing food safety regulations, secondary prevention strategies such as testing food and environmental samples, and tertiary prevention strategies such as providing medical care and isolating infected individuals. These measures can help prevent future outbreaks and reduce the impact of current outbreaks.
