Lesson 1 Activity
“Using Surveillance Data to Describe Influenza Activity”
PARTICIPANT GUIDE
Objectives

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Describe geographic spread of infections and deaths
Describe disease burden using laboratory-confirmed influenza from influenza-like
illness (ILI) cases
Describe severity using laboratory-confirmed influenza from severe acute respiratory
infection (SARI) cases
Describe groups at high-risk for severe disease using surveillance data
Instructions
In this activity, you will work with influenza surveillance data from the fictional country of
Los Olmos to describe the data using descriptive measures. Answer the following questions
using the background information and graphs displayed below.
Time allotted: 1 hour
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Background
You are the Chief Surveillance Officer in Los Olmos. You have been asked to
submit a report describing epidemiological data you have collected on
pandemic (H1N1) 2009 cases. The data have been collected over several
epidemiologic weeks throughout all 6 districts in your country.
Map of Los Olmos:
Mariposa
Los Olmos General Facts:
Geography: Varied—includes coastal areas and highlands
Climate: Tropical; rainy season traditionally occurs from May - October
Capital, Largest City: Mariposa--population 1,102,003 (District 2)
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Population of Los Olmos, overall and by sex, age, and district:
N
Total
%
6,339,479
4
Sex
Male
3,106,345
49%
Female
3,233,134
51%
0-4
733,542
11%
5-24
2,471,488
40%
25-49
1,874,880
30%
50-64
754,294
12%
65+
505,275
7%
District 1
887,527
14%
District 2
1,775,054
28%
District 3
1,331,291
21%
District 4
760,737
12%
District 5
507,159
8%
Age
1. Question
Suggested answer:
2. Question
District
Suggested answer:
\
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District 6
1,077,711
*N= Population size
17%
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Questions
1. You have collected the data for the past four epidemiologic weeks in the table below.
Before you begin your report, what questions do you have about the quality of the data?
Table 1: Counts and percentages of samples positive for pandemic (H1N1) 2009
influenza by PCR among ILI cases, by district, epidemiologic weeks (EW) 44–47, 2009
District*
Population
Pandemic Influenza Positivity
Epi Week
45 n(%)
46 n(%)
15 (10.0)
30 (32.0)
1
887,527
44 n(%)
0
47 n(%)
0
2
1,775,054
25 (11.0)
60 (28.0)
70 (30.0)
80 (38.0)
3
1,331,291
10 (8.0)
0
8 (5.0)
7 (4.0)
5
507,159
0
3 (75.0)
0
0
6
1,077,711
11 (5.0)
25 (15.0)
0
0
Overall
6,339,479
46 (8.0)
103 (14.0)
108 (18.0)
87 (20.0)
Source: National Laboratory of Los Olmos
* District 4 does not have any surveillance sites
2. Once you have reviewed the data for quality, you use it to create the graph below,
which shows the percent of laboratory-confirmed cases for pandemic influenza A
(H1N1) from ILI surveillance by district, for the month of November 2009. Based on
this information, how would you describe the geographic spread of pandemic influenza
(H1N1) during November?
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80
Percent of ILI cases with laboratory-confirmed pandemic
(H1N1) 2009, by district, November 2009, Los Olmos
Percent Positivity
70
60
50
40
30
20
10
0
44
district 1
45
46
Epidemiologic Week
district 2
district 3
47
district 5
district 6
3. What other information would you want to know about the increase of cases in certain
districts? How would you find that information?
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4. The table below shows the cumulative number of laboratory-confirmed pandemic
(H1N1) 2009 deaths in Los Olmos between May and December 2009 by district. What
does knowing the incidence rate for each district allow you to do?
Table 2: Counts of deaths and mortality rates for pandemic influenza A/ H1N1, by
district, Los Olmos, 2009
Incidence Rate
(per 100,000
population)
District
Population
Confirmed
Deaths
1
887,527
27
3.0
2
1,775,054
34
1.9
3
1,331,291
16
1.2
4
760,737
5
0.7
5
507,159
2
0.4
6
1,077,711
9
0.8
Overall
6,339,479
93
1.5
Source: Los Olmos National Laboratory
5.Two blank maps of Los Olmos are provided below. On the first map, use the mortality data
to show geographic spread using death counts. On the second map, use the mortality data
to show geographic spread using the incidence rate. (Hint: You will need to choose case
or rate ranges to accompany each category (very high, high, moderate, and low). Choose a
different color or pattern for each category and shade each district on the map according to
the category under which it falls. NOTE: Do not forget to include the rate or case
ranges on the legend so others can interpret your graph)
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Geographic Spread, Confirmed Deaths
District 1
District 6
District 2
District 5
District 3
District 4
Very High:
High:
Moderate:
Low:
Geographic Spread, Mortality Rate
District 1
District 6
District 2
District 5
District 3
District 4
Very High:
High:
Moderate:
Low:
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6. When reporting the data, which map would you choose to use to present mortality?
Explain your decision.
7. Based on the maps you created, how would you describe the geographic spread of
H1N1 deaths in Los Olmos? What are the possible explanations for the patterns you
see?
8. Review the data contained in the table below which shows confirmed cases of
pandemic (H1N1) in Los Olmos, by sex, between May and December 2009. Describe
which group is at higher risk of infection. Do these data tell you why there is a
difference between the two groups?
Table 3: Counts, percentages, and rates of pandemic (H1N1) 2009 cases, by sex, Los Olmos,
May through December 2009
Sex
Male
Population
3,106,345
N (confirmed cases)
480
Percent of cases
47%
Rate (per 100,000)
15.4
Female
3,233,134
6,339,479
551
53%
17.0
1031
100%
16.3
Total
Source: Los Olmos National Laboratory
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Graph 4: Influenza-like illness cases by epidemiologic week, Los Olmos 2009-2010.
Source: Epidemiologic surveillance Los Olmos
9. Using graph 4, describe the differences in the 2009 and 2010 influenza seasons, as
compared to the baseline (2003-2008).
Graph 5: Percent of hospitalizations for severe acute respiratory infection among all
hospitalized cases, Hospital Juarez, Mariposa, 2008–2009
2008
Percent SARI
2009
Epidemiologic Week
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Epidemiologic Analyses of Influenza Laboratory Data Page
10. From the graph above, describe the patterns of SARI cases in Los Olmos during
epidemiologic weeks 40-52 (approximately mid-October through December), 2009?
Also, discuss what additional information is necessary to assess if the patterns seen in
2009 indicate greater severity.
11. Do the influenza surveillance data from this activity allow you to identify populations
at highest risk for influenza infection? What about populations at highest risk for
serious complications after infection?
References
PAHO Health Surveillance and Disease Management Area. PAHO-CDC Generic Protocol
for Influenza Surveillance. December 2006. Available at
http://www.paho.org/English/AD/DPC/CD/flu-snl-gpis.pdf. Accessed February 11, 2010.
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Epidemiologic Analyses of Influenza Laboratory Data Page