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ANSWER SHEETS DIVISION C

DISEASE DETECTIVES National Science Olympiad

This event includes 2 parts

University of Central Florida Orlando, FL

May 16 – 17, 2014

Developed by the Career Paths to Public Health Program

Division of Scientific Education and Professional Development Center for Surveillance, Epidemiology and Laboratory Services

Centers for Disease Control and Prevention (CDC)

p1 p2 p3 p4 p5 p6 p7 p8 p9 p10

p11 p12 p13 p14 p15 p16 p17 p18 p19 p20



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INSTRUCTIONS FOR 2014 DISEASE DETECTIVES EVENT

The scenarios presented in this event are both hypothetical but are based on actual outbreaks and public health

problems. The format for this event is similar to that used previously except there is a separate questions and

answer sheet. Competitors should write their names and team numbers on both and turn them in at the end of

the event. You may write on the question part but only answers on the answer sheet will be graded. Be sure to

transfer all answers and calculations (where called for) to the answer sheet.



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Division C

Part A: Asthma Outbreak after the Science Olympiad

1. (6 points) Give the definition for “public health surveillance”.

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

2. (15 points) Using the data in Table 1, provide the correct values for each lettered cell (A, B, C, D, E,

F). The data for Orlando are based on a single day, while the data for Florida are for the whole month.

Show your work and express rates with units.

A.

B.

C.

D.

E.

F.

3. (2 points) Which of the cells (A-F) you calculated values for represent(s) cause-specific rates? (enter

the letter for the cell(s))

______________________________________________________________________________



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4. (2 points) Which of the cells (A-F) you calculated values for represent age-specific rates? (enter the

letter for the cell(s))

______________________________________________________________________________

5. (5 points) The rates for Orlando are expressed as emergency department (ED) visits for asthma

/100000/day while those for Florida are expressed as emergency department (ED) visits for asthma

/100000/month. Because of this, they are not directly comparable. Make the overall rates comparable

and calculate the overall relative risk of emergency department (ED) visits for asthma among Orlando

residents as compared to Florida residents. Show your work.

6. (1 point) Based on the differences in the age-specific rates, among which group might there be an

outbreak?

______________________________________________________________________________

7. (3 points) Circle three reasons why is it important for Disease Detectives to confirm that an event is

unusual before proceeding with the next step.

a. To be sure they are dealing with a real problem

b. To be sure their research papers are published after the investigation

c. To make the most efficient use of limited resources

d. To support the need for additional public health funding and resources

e. To respond to public concerns

8. (6 points) One of the first steps Disease Detectives use in an investigation like this is to confirm the

existence of an outbreak or epidemic as opposed to a cluster. These three patterns differ in the number

of cases involved as well as if there are more cases than usual or expected. Fill in the below table,

writing “Yes” if the pattern involves a large number of cases and “No” if it does not and writing “Yes” if

the pattern involves a more cases than usual and “No” if it does not

Large number of cases More cases than usual

Cluster

Outbreak

Epidemic



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9. (6 points) Complete the below table. For each pattern, indicate if there is enough information to

support calling this situation a cluster, an outbreak, or an epidemic and justify your answer by listing

which of the above attributes (large number of cases or more than expected number of cases) is known

and which, if any, are missing..

Is there enough

information (yes/no)?

Supporting or missing attribute

Cluster (2pt)

Outbreak (2pt)

Epidemic (2pt)

10. (3 points) In the space provided, give three reasons why the problem of ED visits for asthma should

be investigated.

a. ___________________________________________________________________________

______________________________________________________________________________

b. ___________________________________________________________________________

______________________________________________________________________________

c. ____________________________________________________________________________

______________________________________________________________________________

11. (4 points) Disease Detectives frequently use a case definition to identify people with disease or

health conditions in an epidemiologic investigation. List the four basic elements of a case definition.

a. ___________________________________________________________________________

b. ___________________________________________________________________________

c. ___________________________________________________________________________

d. ___________________________________________________________________________

12. (4 points) Develop a case definition for this investigation.

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________



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13. (2 points) The review of ED records from three hospitals showed that 233 children and adults were

treated for asthma during May. Is this enough information to determine whether there is an epidemic?

Explain your answer.

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

14. (2 points) What two pieces of important information does Figure 1 provide?

a. ____________________________________________________________________________

b. ____________________________________________________________________________

15. (2 points) Do you have enough information to determine whether there is an epidemic of asthma?

Explain your answer.

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

16. (1 point) Disease Detectives often use data, such as in Table 2, to create a histogram or bar chart to

visualize cases over time. What is the common name of this histogram or bar chart?

______________________________________________________________________________

17. (1 point) Some of these diagrams may provide clues to only one characteristic of an outbreak, others

may provide clues to two, and still others may provide clues to three. However, these bar charts of

histograms almost never provide hints about which of the following characteristics? (circle the best

answer)

a. Time of exposure

b. Source of exposure

c. Characteristics of case patients

d. Chain of transmission



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18. (4 points) Data in Table 2 show a sharp increase (spike) in reported cases on May 16. Give two

possible explanations for this increase.

a. ___________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

b. ___________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

19. (6 points) Name the three categories of information regarding cases that Disease Detectives use

when applying principles of descriptive epidemiology. Give a specific example of each for this

investigation.

Information category Specific example

20. (2 points) The mean age of patients was 16.1 years. Name two other measures of central tendency

that could have been used to describe age.

a. ___________________________________________________________________________

b. ____________________________________________________________________________

21. (2 points) Calculate the proportions of males and females treated for asthma in an ED on May 16.



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22. (2 points) What do these descriptive statistics suggest about the age of those affected? The gender of

those affected?

Age __________________________________________________________________________

______________________________________________________________________________

Gender _______________________________________________________________________

______________________________________________________________________________

23. (1 point) What term do Disease Detectives use to refer to the type of map in Figure 2?

______________________________________________________________________________

24. (1 point) The geographic distribution of cases in Figure 2 suggests which of the following

hypotheses? (circle the correct answer)

a. Asthma attacks might have been linked to proximity to major roadways.

b. Asthma attacks might have been caused by something near the water.

c. Something might have happened near the grain elevator that caused the attacks.

d. Whatever caused the attacks was spread out evenly across all of Orlando.

25. (2 points) Label each axis of the chart in Figure 3.

X-axis ________________________________________________________________

Y-axis ________________________________________________________________

26. (1 point) Which of the below hypotheses are suggested by this time distribution? (circle the best

answer)

a. The causal exposure was continuous and ongoing.

b. Person-to-person transmission played a role.

c. The causal exposure was acute and represented a point source.

d. The causal exposure involved a long incubation or latency period.

e. None of the above.

27. (1 point) What conclusion(s) about time can you draw from the information in Figure 4?

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________



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28. (1 point) Data from Table 4 can be used to investigate the problem further by identifying links

between each product and asthma epidemic days. Name the specific measure of association Disease

Detectives would use to compare risk in this case.

______________________________________________________________________________

29. (10 points) Calculate the association of each product with asthma epidemic days using information

from Table 4. Then, identify the product with the highest association with asthma epidemic days.

Cement: (2 points)

Wheat: (2 points)

Coffee: (2 points)

Soybeans: (2 points)

Product(s) with the highest association with asthma epidemic days: (2 points)

______________________________________________________________________________

30. (8 Points) The below table includes a number of study design characteristics. Put an X in the

column of the study design for which each characteristic applies. Some apply to both and some apply to

neither design.

Characteristic

Study Design

Case Control Cohort

Start with illness status and look for exposures

Start with exposures and determine illness status

Odds ratio used as measure of risk

May go forward or backward in time

Participants are randomly chosen for exposure

Good for rare illnesses

Good for rare exposures

Relative risk used as a measure of risk



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31. (1 Point) Which of the below groups would you select to serve as controls if you were to do a case-

control study looking for risk factors associated with being seen in an Orlando ED for asthma during the

time period in question? (select best answer)

a. Residents of a local nursing home.

b. Age-matched neighbors who had no history of asthma.

c. Age-matched asthmatics from Miami.

d. Age-matched Orlando residents who had a previous history of asthma but did not need to go

to the ED during the period in question.

e. None of the above.

32. (4 points) The Disease Detectives calculated a test of statistical significance (chi-square) for the

product with the strongest association with epidemic days, with a pre-established cutoff of p = 0.05. The

corresponding p value for the test was p = .007. (4 points) The Disease Detectives calculated a test of

statistical significance (chi-square) for the product with the strongest association with epidemic days,

with a pre-established cutoff of p = 0.05. The corresponding p value for the test was p = .007. Write a 1-

2 sentence explanation for these results that you would give to the press.

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________



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33. (8 points) In investigations such as this, Disease Detectives draw conclusions about cause-and-effect

relationships based on several criteria. List four of these criteria in the table on your answer sheet. For

each criterion, indicate whether and how the criterion was addressed by the information presented in this

Science Olympiad problem. (Hint: You may have heard of these criteria called Hill’s Criteria of

Causation.)

Criterion

Was It

Addressed?

(Yes or No) If Yes, How?

1.

2.

3.

4.

34. (2 points) What are two recommendations Disease Detectives would make to the City of Orlando

and the local school system to help control or prevent future asthma epidemic days among children?

a. ___________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

b. ____________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________



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Part B: Fun at the Child Care Center

1. (1 point) Which of the following represents a key component of the definition of an outbreak? (circle best

answer)

a. It happens suddenly.

b. It involves a lot of people.

c. Some of the people are hospitalized or die.

d. There are more cases than expected.

e. It is caused by an infectious agent.

f. It is widespread.

2. (1 point) Give one more piece of information you need to determine if this is an outbreak.

____________________________________________________________________________________

3. (1 point) Which of the two main branches of epidemiology (descriptive or analytic) are you applying at this

stage of the investigation?

____________________________________________________________________________________

4. (1 point) Which of the following is the most important question you would ask about the children with

diarrhea to address place? (circle best answer)

a. Where do they live?

b. What classroom are they in?

c. Have they traveled out of the area?

d. What other exposures did they have in the week before they became ill?

5. (1 point) Which of the following is the most important question you would ask about the children with

diarrhea to address time? (circle best answer)

a. When was the last day they were at the center?

b. What time of day did they become ill?

c. When did they first attend the center?

d. What day did they become ill?

6. (3 points) Calculate incidence of diarrhea per child-year over weeks 29–36 in 2013.

7. (2 points) Determine the relative risk for diarrhea in 2013 compared with 2012.



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8. (1 point) Which of the below statistical tests would you use to determine the statistical significance of the

difference in rates? (circle best answer)

a. T-test

b. Fishers exact

c. Paired T-test

d. Chi square statistic

9. (1 point) Which part of the descriptive epidemiology triad are you addressing by looking at the data

by classroom?

____________________________________________________________________________________

10. (2 points) List two steps of an outbreak investigation that were addressed in the previous paragraph.

a. __________________________________________________________________________________

b. __________________________________________________________________________________

11. (1 point) What is the APHA recognized mode of transmission for most diarrheal diseases? (Note: fecal –oral

is not one of the APHA recognized modes of transmission)

____________________________________________________________________________________

12. (2 points) Which of the classrooms in Table 2 include children who are not toilet trained (assume all

3-year-olds are toilet trained)?

____________________________________________________________________________________

13. (2 points) If the age distribution of the children at Fun Time Academy changed a great deal between

2012 and 2013, what technique would you need to use to compare the overall illness rates?

____________________________________________________________________________________

14. (16 points [2 points] each) Complete the following table. (Note: the letters correspond to the cells

in the table) Show your calculations and express in units.

A.

B



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C

D

E

F

G

H

15. (2 points) Which of the following statements are supported by the information in Table 2? (circle all that

apply)

a. Diapered children had greater risk for diarrheal illness than toilet-trained children during both time

periods.

b. Both groups experienced greater risk for diarrheal illness in 2012 than in 2013.

c. The excess risk among diapered children compared with toilet-trained children was significantly

greater in 2013 than in 2012.

d. The data support a hypothesis that the increase in diarrheal illness in 2013 involved both diapered and

toilet-trained children.

16. (2 points) You have 12 tests available and need to decide how to use them. Which of the following screening

schemes would you use if you wanted to test the hypothesis that this outbreak is caused by Cryptosporidium?

(circle best answer)

a. Select classrooms with the most ill children and test only those with a recent history of diarrhea.

b. Test only children with a recent history of diarrhea but select only one or two from each classroom.

c. Select one or two classrooms and test a few children with a recent history of diarrhea and a group of

children who have not had diarrhea (controls).

d. Screen a randomly selected group of children with a recent history of diarrhea and a randomly

selected group of children without a recent history of diarrhea.



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17. (2 points) Which of the following screening schemes would you use if you wanted to determine the

prevalence of infection in a group of students?

a. Select classrooms with the most ill children and test only those with a recent history of diarrhea.

b. Test only children with a recent history of diarrhea but select only one or two from each classroom.

c. Select one or two classrooms and test a few children with a recent history of diarrhea and a group of

children who have not had diarrhea (controls).

d. Screen a randomly selected group of children with a recent history of diarrhea and a randomly

selected group of children without a recent history of diarrhea.

e. Select the classroom with the most ill children and test everyone.

18. (4 points) List four of Marge’s observations that could have contributed to this outbreak.

a. __________________________________________________________________________________

b. __________________________________________________________________________________

c. __________________________________________________________________________________

d. __________________________________________________________________________________

19. (3 points) List three of Bill’s observations that are cause for concern in regard to this outbreak.

a. __________________________________________________________________________________

b. __________________________________________________________________________________

c. __________________________________________________________________________________

20. (3 points) Which of the below recommendations would you make concerning this outbreak? (circle all

that apply)

a. Exclude all children with diarrhea until their diarrhea resolved.

b. Screen all children and staff and allow only non-infected persons to enter the facility.

c. Screen all children, staff and household contacts and exclude all persons who were infected or were

household contacts of infected persons until they were no longer infected whether they had diarrhea or

not.

d. Implement a program of daily disinfection of floors, walls, ceilings and other environmental surfaces

throughout the building.

e. Instruct the staff in proper hand washing, diapering and other hygiene activities and monitor their

performance.

f. Exclude children with diarrhea from using water tables.

g. Install hand-sanitizer dispensers throughout the facility and encourage both children and staff to use them

rather than washing their hands.



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.

21. (4 points) The sensitivity of the laboratory test for crypto is 75%, the true prevalence of infection is 20%, and

you screen 100 children. If the specificity is 100%, how many infections will you miss? (Show your

calculations.)

22. (4 points) If you were to screen each child twice and consider a child to be infected if either specimen is

positive, what would be the sensitivity of the test? (Show your calculations.)

23. (2 points) Give two explanations for the four negative test results from children with symptoms.

a. _________________________________________________________________________________

____________________________________________________________________________________

____________________________________________________________________________________

____________________________________________________________________________________

b. _________________________________________________________________________________

____________________________________________________________________________________

____________________________________________________________________________________

____________________________________________________________________________________

24. (4 points) Now that you have a good idea about the agent responsible for this outbreak, write a case

definition that you can use for the remainder of the investigation.

____________________________________________________________________________________

____________________________________________________________________________________

____________________________________________________________________________________



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25. (2 points) What was the prevalence of Cryptosporidium infection among children and staff at Fun

Time Academy? (Show your calculations.)

26. (4 points) Using the laboratory test as the gold standard for identifying persons with

Cryptosporidium infections, what is the specificity of using watery diarrhea as an indicator? (Show your

calculations.)

27. (2 points) What does this suggest to you about where the outbreak started and where it ended?

____________________________________________________________________________________

____________________________________________________________________________________

____________________________________________________________________________________

28. (3 points) Based on what you have been told about the practices and conditions in this child care

facility, list three ways that Cryptosporidium infection would have spread from one of the above groups

to the other.

a. _________________________________________________________________________________

b. _________________________________________________________________________________

c. _________________________________________________________________________________



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29. (2 points) How can you explain the fact that your prevention measures were started at the beginning

of week 37 yet the greatest number of cases in both diapered and toilet-trained persons occurred during

that week (i.e., were your measures effective or not)?

____________________________________________________________________________________

____________________________________________________________________________________

____________________________________________________________________________________

30. (6 points) List three broad recommendations you would make for all child care programs in your

area to prevent this sort of outbreak from happening again.

a. _________________________________________________________________________________

____________________________________________________________________________________

____________________________________________________________________________________

b. _________________________________________________________________________________

____________________________________________________________________________________

____________________________________________________________________________________

c. __________________________________________________________________________________

____________________________________________________________________________________

____________________________________________________________________________________

Documents

ANSWER SHEETS - Mr. Dimmer's Website