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Science Olympiad » Disease Detectives Event» National Event Exercises
West Nile Virus


   

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West Nile Exercise
 

Answer Key

1. Define Public Health Surveillance.

Answer (5 points, one for each element)

  • Ongoing collection
  • Analysis
  • Interpretation
  • Dissemination
  • Action linked to health and risk factor information

2. Based on the data in Table 1, for which two age groups was the apparent risk of West Nile virus infection greatest? In the space in Table 1, show each calculation to support your answer and give all units. (Note: units must be given to receive credit.)

Answer (4 points, 1 pt for each correct age group, 1 for each corresponding calculation; must express as # cases/population/2 months, or 1 month) Age groups 70-79 and 80+. See table for calculations and units.

Table 1. Number of hospitalized patients with laboratory confirmed West Nile virus infection, New York City Department of Health, August 1 September 31, 1999.

Age (yrs) No. Patients (%) Population at Risk Calculations
0-19 2 (3) 2,324,081 Rate/100K/2mo
2 2,324,081 = 0.09

Rate/100K/1mo
(2 2,324,081) 2 = 0.05

20-29 1 (2) 1,553,981 Rate/100K/2mo
1 1,553,981 = 0.06

Rate/100K/1mo
(1 1,553,981) 2 = 0.03

30-39 3 (5) 1,549,111 Rate/100K/2mo
3 1,549,111 = 0.19

Rate/100K/1mo
(3 1,549,111) 2 = 0.10

40-49 1 (2) 1,177,190 Rate/100K/2mo
1 1,177,190 = 0.08

Rate/100K/1mo
(1 1,177,190) 2 = 0.04

50-59 9 (15) 867,331 Rate/100K/2mo
9 867,331 = 1.04

Rate/100K/1mo
(9 867,331) 2 = 0.52

60-69 13 (22) 814,838 Rate/100K/2mo
13 814,838 = 1.60

Rate/100K/1mo
(13 814,838) 2 = 0.80

70-79 18 (31) 534,785 Rate/100K/2mo
18 534,785 = 3.37

Rate/100K/1mo
(18 534,785) 2 = 1.69

greater than or equal to 80 12 (20) 281,054 Rate/100K/2mo
12 281,054 = 4.27

Rate/100K/1mo
(12 281,054) 2 = 2.14

Sex (yrs) No. Patients (%) Population at Risk Calculations
Male 31 (53) 4,289,988 Rate/100K/2mo
31 4,289,988 = 0.72

Rate/100K/1mo
(31 4,289,988) 2 = 0.36

Female 28 (47) 4,812,383 Rate/100K/2mo
28 4,812,383 = 0.58

Rate/100K/1mo
(28 4,812,383) 2 = 0.29

 

3. For which single age group was the apparent risk the least? In the space in Table 1, show a calculation to support your answer and give all units. (Note: units must be given to receive credit.)

Answer (2 points, 1 for each correct age group and 1 for calculation: must express as # cases/population/week, month, or 2 months). Age Group 20-29; See table for units.

4. Given that mosquitoes transmit this disease, give two explanations for the age distribution.

Answer (2 points, 1 per valid answer)

  • Older people are more likely than other groups to be bitten by mosquitoes: they may be less likely than others to use protective measures, or they may keep windows open for lack of air conditioning.

  • Older people are more susceptible than others to infection.

  • Older people are more likely than others to seek medical care: they may have severe disease and be hospitalized.

(Note: Students may give reciprocal answer concerning younger people.)

5. For which gender group is the risk of infection highest? In the table, show your calculations and give all units. (Note: units must be given to receive credit)

Answer (2 points). 1 point for group (men) and 1 point for calculation with units.

6. For the group you determine to be at greatest risk, give one explanation that might account for the increased risk.

Answer (1 point)

  • They may be outside more.

  • They may be less likely to wear mosquito repellent.

7. From Table 2, the relative risk of death among people with diabetes mellitus appears to be substantially increased. Explain the quantitative meaning of this relative risk.

Answer (2 points, 1 for quantifying risk elevation and 1 for mentioning reference group). The risk of death from West Nile virus infection for people with diabetes is 5 times greater than that for people without diabetes.

 




This page last reviewed August 27, 2004

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