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Science Olympiad » Disease Detectives Event » Sample Problems and Answer Keys
Problems: E. coli

Read the following articles on the E. coli O157:H7 outbreak in Milwaukee.

See Also...
Answer Key

Outbreak of Escherichia coli O157:H7 Infection Associated With Eating Fresh Cheese Curds  
Wisconsin, June 1998. Morbidity and Mortality Weekly Report. October 13, 2000. 49(40):911-913.

Epidemiologic Notes and Reports Isolation of E. coli O157:H7 from Sporadic Cases of Hemorrhagic Colitis  
United States Morbidity and Mortality Weekly Report. August 1, 1997. 46(30):700-704.


1. What was the odds ratio of persons who ate watermelon and becoming ill? (2 points). 

a. 8 
b. 15 
c. 800 
d. 62 

2. What is the term that means a pathogen is transferred from one food item to another food item? (3 points) 

a. sabotage 
b. cross-contamination 
c. incubation period 
d. mode of infection 
e. bio-terrorism 

3. Give two examples of the above. (2 points each) 


4. Why are antibiotics discouraged to treat E. coli O157:H7 infections in children? (2 points) 


5. One of the articles discusses confirmed cases, probable cases, and possible cases. Investigators determine these categories by defining: (2 points) 

a. the incubation period 
b. the source of exposure 
c. the mode of transmission 
d. the case-definition 

6. Write an example of this for confirmed case-patients that the investigators in this outbreak may have used. (5 points) 


7. What is the case-fatality rate of this outbreak, using the combined number of confirmed and probable case-patients. (4 points) 

a. 0.14% 
b. 0.18% 
c. 1.61% 
d. 0.16 % 

8. Calculate the odds ratio given the following data. (4 points) 


Ill Ate watermelon Did not eat watermelon Total
Yes 72 115 187
No 5 122 127
Total 77 237 314


a. 15.3 
b. 14.4 
c. 9.8 
d. 18.7

Answer Key


Match the disease with mode of transmission.

1. ___ Hepatitis A A. Tick-borne
2. ___ Hepatitis B B. Blood/sexual
3. ___ HIV C. Food-borne/fecal-oral
4. ___ E. coli O157:H7 D. Mosquito-borne
5. ___ West Nile Virus E. Unknown 
6. ___ Lyme Disease  
7. ___ Kawasaki Disease  
8. ___ Campylobacter  
9. ___ Rocky Mountain Spotted Fever  
10. ___ Malaria  

Answer Key

This page last reviewed April 24, 2007

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