Epidemiology Case 3

MEASURES OF ASSOCIATION

As an epidemiologist for the County Disease Control Office, you are investigating an outbreak that occurred at a restaurant. The predominant symptoms included vomiting (81%), nausea (76%), and diarrhea (76%). The average incubation period was five hours with an average duration of 19 hours. Items consumed among the ill included prime rib, baked potato with butter, and green salad with dressing.

Figure 1:

FOOD ITEMS	PERSONS WHO ATE SPECIFIED FOOD	PERSONS WHO DID NOT EAT SPECIFIED FOOD
	Ill	Not Ill	Total	Ill	Not Ill	Total
Prime Rib	18	3	21	3	5	8
Baked Potato	19	4	23	2	4	6
Green Salad	18	9	27	1	1	2

Figure 2:

Food Item	95% Confidence Interval
Prime Rib	1.4 - 65.7
Baked Potato	1.6 -218.5
Green Salad	.10 - 42.9

Case Assignment

Your task for this Case Assignment is to answer these questions:

1. What type of study was used for this investigation? Explain.

2. What would be the appropriate measure of association for this study?

3. Calculate the food-specific attack rates and calculate the measure of association between illness and each food item.

4. What does a confidence interval mean, and which 95% confidence intervals are statistically significant?

5. What do the results indicate regarding the likely source of exposure?

Assignment Expectations

Length: Case assignments should be at least 5 pages (1250 words) in length.

Required Reading/Useful Resources:

Centers for Disease Control and Prevention. (2012). Lesson one: Introduction to epidemiology: Lesson 3 Section 5: Measure of Association. Principles of Epidemiology in Public Health Practice, 3rd Edition. Retrieved May 1, 2019, from  https://www.cdc.gov/csels/dsepd/ss1978/lesson3/section5.html

Centers for Disease Control and Prevention. (2009). Outbreak of Salmonella serotype Saintpaul infections associated with eating alfalfa sprouts - United States, 2009. Morbidity and Mortality Weekly Report, 58(18), 500-503. Retrieved on May 22, 2012, from  http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5818a4.htm

Meirik O. (n.d.). Cohort and case-control studies. Retrieved May 1, 2019, from  http://www.gfmer.ch/Books/Reproductive_health/Cohort_and_case_control_studies.html

Thiese, M. S. (2014). Observational and interventional study design types; an overview. Biochemia Medica, 24(2), 199. Available via EBSCOHOST