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Student Name(s) ______________________________________________

______________________________________________ School Name ______________________________________________ Team Name/Number _________________________________________

KEY 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

School and team number: ________________________________________________________

Pts earned on this page_______________

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.



Division C

Part A: Asthma Outbreak after the Science Olympiad

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

Public health surveillance: the systematic, ongoing collection, analysis, interpretation, and

dissemination of health data for disease control and prevention.

Definition should include SYSTEMATIC, ONGOING, COLLECTION, ANALYSIS, INTERPRETATION and

DISSEMINATION of HEALTH DATA for DISEASE CONTROL AND PREVENTION or their synonyms.

Subtract 1 pt for each missing concept until you reach 0.

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. 100 (1 pt) – no calculations necessary

B. 32 (1 pt) – no calculations necessary

C. 132 (1 pt) – no calculations necessary

D. Age-specific ED visit rate (100/52408)x100,000= 190.8 per 100,000 population per day

E. Cause-specific ED visit rate (132/249562)x100,000= 52.9 per 100,000 population per day

F. Age-specific ED visit rate (4676/15263392)x100,000= 30.6 per 100,000 population per month

Score 1 point for each correct value. For rate calculations, add 1 additional point for (a) formula shown for rate,

(b) per 100,000 or other unit with each rate, (c) some statement of time e.g., per month or in May…for a total of

4.0 points per rate calculation

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))

E .



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

letter for the cell(s))

____D,F______

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.

IORL=(132 ED visits/day)/249562 persons = 52.9 EDvisits/day/100000 persons (1 pt)

IFL=(8654 ED visits/month)/19320749 persons=44.8 EDvisits/month/100000 persons (1 pt)

RR = IORL/IFL (Note – the “hook’ here is that both incidence rates have to have the same time frame – IORL should be

converted to ED visits/month or IFL should be converted to ED visits/day. This is done by either multiplying or dividing the

IORL or IFL by 31, respectively since there are 31 days in May). Doing this correctly shows an understanding of incidence and

relative risk and is worth 2 points. Attempts to do this show a recognition but not mastery and is worth 1 point.)

RR = (1639 ED visits/mo/1000000)/(44.8 ED visits/mo/1000000) = 36.6 OR

RR = (52.9 ED visits/day/1000000)/(1.4 ED visits/day/1000000) = 36.6 (1 pt.)

A RR of 1.18 shows they did not get the time difference and is worth 2 pts for the whole question.

Any other RR is worth 1 pt for the whole question.

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

outbreak?

may be an outbreak among persons aged 17 or less

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 YES NO

Outbreak NO YES

Epidemic YES YES



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) Yes The number is large

Outbreak (2pt) No Expected Number is Unknown

Epidemic (2pt) No Expected Number is Unknown

(1 pt per cell, 2nd

column – look only for the above answers)

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

be investigated.

1. Control and prevention; Severity and risk to others; Public, political, or legal concerns,

Program considerations; Training opportunities, Research opportunities 2. For asthma

specifically: Asthma related emergency department visits and hospitalizations are indicators of

uncontrolled asthma. Asthma can be a life-threatening disease if not managed properly (via access

to primary care physicians, preventive medicine, and health education).

1 pt each - scorer judgment - Accept any three of the above or other reasonable answers – do not accept two

versions of same concept – e.g. prevent severe disease and keep people from dying, prevention and control can be

counted as two.

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) Clinical information about the disease (1pt)

b) Information about the location or place (1pt)

c) Characteristics about the people who are affected (1pt)

d) A specification of time during which the outbreak occurred (1pt)

The above or paraphrase in any order.

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

Be flexible as long as each of the above 4 elements are addressed – need not be complete. Score: 1 Point for each

element of a case definition

Example : “A case is any person with (a) a doctor’s diagnosis of asthma (b) who visited an ER in

Orlando for (c) breathing difficulties (d) during the month of May, 2012.”



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.

No (1pt).

Although the large number of cases was observed over a large geographic area, we still need to know

the expected number of ER visits for asthma at these hospitals for the same time period in the past

(1pt).

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

a. _Baseline numberof ED visits___________________________________

b. _Number of visits on May 12 increased________________________________________

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

Explain your answer.

Yes (1pt), there is an increase over baseline rate in May...the graph shows an unusual increase

over the background rate (1pt).

Accept “No” if they say that area is small or unknown and the situation represents an outbreak.

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?

_____Epi curve or Epidemic curve_____

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



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.

Scorer discretion - 2 pts per explanation Examples of possible answers include: Improved reporting;

Increased awareness or publicity; Greater number of susceptible people (more people with

asthma); New systems in place to detect cases (increased ascertainment); Incorrect diagnoses from

health care providers; Laboratory error (pseudo outbreaks); False positive test results; Real

outbreak

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

Person (1 pt) age, race, sex, occupation, behavior (1pt)

Place (1 pt) place of residence, place of work, place of social activity, room

in a building, travel (1pt

Time (1 pt)_ date of onset, date of diagnosis, date of report to health

authority, date of hypothesized exposure (1pt)

Scorers – must have person, place and time in column 1 (any order), aceept any appropriate example for column

2.

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.

Median and mode – any order

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

Proportion male = 48/103 = 46.6%

Proportion male = 55/103 = 53.4%



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

those affected?

Age _____Individuals tended to be younger__________________________________________

______________________________________________________________________________

Gender ___Roughly equal in males and females_______________________________________

______________________________________________________________________________

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

______Spot map_________________________________________________________________

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 _____ hour of onset or onset time_____________________________________

Y-axis ____ number of cases ______________________________________________

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?

For May 2012, the pollen, & mold levels remained well below normal levels for Orlando in May



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.

________ODDS RATIO____________________________________________________________

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

from Table 4. (show your calculations) Then, identify the product with the highest association with

asthma epidemic days.

Basic setup is

Epi day No epi day

Exposure A B

No exp C D

Cement: (2 points) A= 5, B=150, C=9, D=461, OR = 1.7

Wheat: (2 points) A=9, B=413, C=4, D=300, OR = 1.6

Coffee: (2 points) A=11, B=482, C=2, D=125, OR = 1.4

Soybeans: (2 points) A=15, B=259, C=1, D=478. OR= 27.7

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

___Soybeans______________________________________________________

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. (1 pt per row - .5 pt per cell)

Characteristic

Study Design

Case Control Cohort

Start with illness status and look for exposures X

Start with exposures and determine illness status X

Odds ratio used as measure of risk X X

May go forward or backward in time X

Participants are randomly chosen for exposure

Good for rare illnesses X

Good for rare exposures X

Relative risk used as a measure of risk X



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?

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. Write a 1-2 sentence explanation for these results that

you would give to the press.

The results from our investigations indicate the problem was most likely due to soybean dust

generated by unloading soybeans at an area grain elevator. Problems were 28 times more likely

to occur on days when soybeans were unloaded than on days when soybeans were not unloaded.

The likelihood of observing this great a difference by chance was 0.7 percent or 7 out of 1000 times

(give 1 point for trying and 1 point for addressing each of the above underlined statements)

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. Strength of the

association:

YES High odds ratio and statistical significance

2. Temporality: Probably YES

3. Dose-response: No

4. Consistency/coherence: no No

5. Biologic plausibility: yes Yes Soy bean dust is known allergen

6. 1-1 relationship: no No

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?



Scorers – accept any reasonable recommendation (3 are listed below). Prohibiting delivery of soy

products and closing elevator is an unreasonable recommendation – give half credit.

Install engineering controls to contain soy dust at the grain elevator.

Notify local school and events when soy shipments are scheduled.

Educate local medical staff & schools about the potential exposure & outcomes.



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?

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.

_____Expected or baseline number of cases of diarrhea_____________________________________

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

stage of the investigation?

______Descriptive_____________________________________________________________________

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.

Incidence = (32*52)/1124 = 1.48 cases per child-year

(1 pt for correct numerator, 1 pt for correct denominator, 1 pt for adjusting week data to year)

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

RR = 1.48/0.61 = 2.41



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 points) Which part of the descriptive epidemiology triad are you addressing by looking at the data

by classroom?

PLACE (1 pt for PERSON since classroom and age are linked)

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

Prepare for fieldwork

Verify the diagnosis

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)

_________________________VEHICLE_____________________________________________

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)?

________________________1 A&B and 2 A&B____________________________________________

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?

______Direct age adjustment (1 pt for stratified analysis or age adjustment, .5 pt for adjustment)_________

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

in the table)

A. I diapered 2012 = 8 ill children /250 child-weeks = 0.023 ill children/child-week

B. I diapered 2013 = 20 ill children /362 child-weeks = 0.06 ill children/child-week

C. RR diapered 2013/diapered 2012 = I diapered 2013 / I diapered 2012 = 0.06/0.023 = 2.42

D. I toilet trained 2012 = 7 ill children/750 child-weeks = 0.0067 ill children/child-week

E. I toilet trained 2013 = 12 ill children/762 child-weeks = 0.0157 ill children/child-week



F. RR toilet-trained 2013/toilet trained 2012 = I toilet trained 2013 /I toilet trained 2012 = 0.0157/0.0067 = 2.36

G. RR diapered 2012/ toilet trained 2012 = I diapered 2012/ I toilet trained 2012 = 0.023/0.0067 = 3.43

H. RR diapered 2013/ toilet trained 2013 = I diapered 2013/ I toilet trained 2013 =

(give 1 point for plugging in right cells and 1 point for right answer )

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.

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.

1. one of the aids wash the kid’s backside off in the sink before diapering him

2. sink had a bunch of toys in it

3. kids were helping pass out cookies

4. were very careful and all used hand sanitizer



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

1. all used hand sanitizer before water play

2. see a couple of the kids drinking the water

3. emptied and cleaned out at the end of the day

4. hose them out, turn them upside down and let them air dry

5. toys used in the water tables are just allowed to air dry

(any three of the above)

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.

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.)

Sensitivity = .75% Sensitivity = TP/(TP+FN) Prevalence = 20% of 100 = 20 = TP+FN

.75 = TP/20 TP=.75X20=15 FN=20-15=5

(1 pt for right formula for sensitivity, 1 pt for correct use of prevalence, 1 pt for putting data in correctly, 1 pt for

correct answer)

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.)

Sensitivity = TP/(TP+FN) = .75 = .75/1 FN = 1-.75 = .25 = probability of being FN on one test, probability

of being FN on two tests = .252

Sensitivity of two tests = 1-.252 = .9375

(4 pts for correct answer, 3 pts for focusing on .25, 2 pts for focusing on .75, 1 pt for knowing sensitivity

would improve)



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

Their illness was caused by something other than crypto

There was an error in the test or collection

They had recovered when the specimens were collected

Accept any of the above or variants

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.

Clinical information about the disease (1pt) – history of watery diarrhea

Information about the location or place (1pt) – fun time academy

Characteristics about the people who are affected (1pt) – staff or child

A specification of time during which the outbreak occurred (1pt) - between week 34 & 40, 2013

(accept positive test for Crypto instead of or with watery diarrhea – give 1 pt extra if they use this as

confirmed vs suspect cases)

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

Time Academy? (Show your calculations.)

Prevalence = 51/183 = 27.9%

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.)

Specificity = TN/(TN+FP) = 120/(120+32) = 90.9%

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

It appears the outbreak started in the diapered children and then spread to the toilet-trained children

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.

Scorers – accept any reasonable answer. Examples given below.

Shared same water tables



Transmission at home

Transmission in early drop-off and late pick-up groups

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)?

Measures were effective. Crypto has a fairly long incubation period and those who became ill during week

37 were probably infected before prevention measures were implemented.

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. Educate staff and parents

b. Exclude any child with diarrhea from the child care setting until the diarrhea has stopped

c. Establish, implement, and enforce policies on water-play and swimming

d. Practice good hygiene.

e. Reinforce good diapering practices

f. Disinfect surfaces and objects, including but not limited to bathrooms, diaper-changing areas, food-

preparation areas, tabletops, high chairs, and toys.

g. Notify the state or local health department about an excessive level of diarrhea or any Crypto cases in

the child-care facility. Crypto is a nationally reportable disease.

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