Introduction To Epidemiology

Answer the following questions:

  1. A flu outbreak occurred in a military barracks that housed 20 soldiers. Case A was diagnosed on October 1 and Case B was diagnosed on October 2. After approximately 10 days, 12 additional cases occurred during approximately a 1 week time span. Military epidemiologists believe that this second group of 12 cases represented another generation of cases. None of the 20 soldiers was known to be immune to the disease. Calculate the secondary attack rate using the forgoing data.
  2. A local health department epidemiologist investigated an outbreak of gastrointestinal illness thought to be associated with a college cafeteria. There were many complaints about the quality of the cafeteria’s offerings, and it appeared that the student’s worst expectations were confirmed when several students visited the college’s infirmary during the middle of the night and the following day complaining of nausea, diarrhea, fever, vomiting, and cramps. The health department’s investigation revealed that 24 students had eaten in the cafeteria and the development of active symptoms ranged from 24 to 36 hours. A list of foods eaten, the number of persons eating the foods, and the tabulations of illness are presented. Fill in the attack rates where indicated. On the basis of your calculations answer the following questions:
    1. What food or foods would you suspect caused the problem?
    2. Based on the description of the clinical symptoms what agent(s) do you think was (were) responsible? ( Your best guess, no points will be deducted for wrong answers to this question)
    3. Calculate the rate of illness in those who ate the food and those who did not eat the food.

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Introduction To Epidemiology

Outbreak Investigation

Overview of exercise

In this exercise you will read a description, then answer questions in the space provided.

 

1. A flu outbreak occurred in a military barracks that housed 20 soldiers. Case A was diagnosed on October 1 and Case B was diagnosed on October 2. After approximately 10 days, 12 additional cases occurred during approximately a 1 week time span. Military epidemiologists believe that this second group of 12 cases represented another generation of cases. None of the 20 soldiers was known to be immune to the disease. Calculate the secondary attack rate using the forgoing data.

 

2. A local health department epidemiologist investigated an outbreak of gastrointestinal illness thought to be associated with a college cafeteria. There were many complaints about the quality of the cafeteria’s offerings, and it appeared that the student’s worst expectations were confirmed when several students visited the college’s infirmary during the middle of the night and the following day complaining of nausea, diarrhea, fever, vomiting, and cramps. The health department’s investigation revealed that 24 students had eaten in the cafeteria and the development of active symptoms ranged from 24 to 36 hours. A list of foods eaten, the number of persons eating the foods, and the tabulations of illness are presented.

 

a. First fill in the attack rates where indicated in table 1 located on page two.

b. Next, on the basis of your calculations answer questions on page two and three.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 1. Data from a Foodborne Illness Outbreak in a College Cafeteria

 

Number of Person who ate Number of Persons who did not eat
Food items served III Not III Total %III III Not III Total %III
Three Bean Salad 10 3 13   7 4 11  
Beef, rare 17 6 23   0 1 1  
Beef, specified well cooked 3 6 9   5 10 15  
Potatoe Salad 12 6 18   4 2 6  
Macaroni Salad 11 5 16   5 3 8  
Tuna Salad* 13 1 14   3 7 10  
Cold Cuts and

Cheese plate

10 6 16   5 3 8  
Rolls and Butter 13 4 17   4 3 7  

 

 

Note. The tuna salad was prepared from fresh ingredients approximately 1 hour before consumption and stored under refrigeration.

 

 

 

A. What food or foods would you suspect caused the problem? (Review table on page 2.)

 

 

 

B. Based on the description of the clinical symptoms what agent(s) do you think was (were) responsible? ( Your best guess, no points will be deducted for wrong answers to this question)

 

 

 

C. Calculate the rate of illness in those who ate the food and those who did not eat the food.

 

 

 

D. Calculate the rate differences. The Rate Difference is the rate of disease in the exposed or ill population minus the rate of disease in the unexposed or well population.

 

 

 

E. Staff then decided to perform a case control study to determine the risk associated with eating at cafeteria. In addition to the 24 individuals who had eaten in the cafeteria and who presented ill in the college’s infirmary, staff identified an additional 6 individuals who were also seen in the infirmary with similar symptoms but who had not eaten in the cafeteria. Staff began interviewing additional students that were the same gender, and within + 5 years of the age of the cases. Staff identified 76 individuals who were not sick and who also had eaten in the cafeteria on the day in question and 94 students who also were not ill and who had not eaten in the cafeteria on the day in question. What is the risk of become ill from eating in the cafeteria?

 

 

 

F. Calculate the odds ratio; that is the risk of becoming ill from eating in the cafeteria.

 

 

 

3

 
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