1. Influenza pandemic: FluWorkLoss: Software to estimate work days lost
Martin I. Meltzer, Ph.D.
Senior Health Economist & Distinguished Consultant
Division of Emerging infections and Surveillance Services
NCDPCID
Centers for Disease Control and Prevention (CDC)
Atlanta, GA, USA.

2. Influenza epidemiology
Who gets sick?
How many get sick?
What happens to them (how sick)?
When do they get sick?

3. Predominant type/subtype
U.S.: Variations by Year in Influenza-Related Respiratory and Circulatory Deaths
Estimated annual deaths
Predominant type/subtype
Year
Ave. no.
deaths/year
H1N1
4,692
40,457 B
16,036
H3N2+ B
24,562
H3N2
52,148
Source: Thompson, et al. JAMA 2003; 289:

4. U.S. Influenza-related Respiratory and Circulatory Deaths: By age
Age group (years)
Average ‘flu deaths
< 1 26
1-4 66
5-49
789
50-64
2,626
65+
32,651
Average total
36,155
Annual totals vary from 17,056 – 51,296
Source: Thompson, et al. JAMA 2003; 289:

5. Source: Meltzer et al. Vaccine 2005;23:1004-1014
Variability: Distribution of risk of hospitalization due to ‘flu: 6-23 mths, (non-high risk)
Actual data: Median 194/100,000
Frequency
-600
-400
-200
200
600
400
800
1000
1200
1400
Rate of hospitalization/ 100,000
Source: Meltzer et al. Vaccine 2005;23:

6. Hospitalizations/ 1,000 for 6–23 months: Non-high and high risk groups
Source: Meltzer et al. Vaccine 2005;23:

7. Influenza-related Hospitalizations per 100,000 Persons*
Age Group
Non-high Risk
High Risk
0 - 4
100
500
5 - 14 20
200
65+
N/A
200 - >1000
*(Barker, Am J Epi, 1980; Glezen, Am Rev Resp Dis, 1987; Can J Infect Dis, 1993)

8. Some conclusions: Impact varies
By year, sometimes greatly (range: +/ - 50%)
By age (2- 5 times or more)
By risk: high risk vs. non-high risk (2 – 10 times)
SO: When evaluating potential impact:
Must allow for variations – even pandemics

9. Pandemic influenza When will the next pandemic occur?
How many deaths, hospitalizations, outpatients, and ill, self care?
Economic and other impacts
Implications for policy

10. When will the next ‘flu pandemic occur?
Time between start of pandemics
Years between start of pandemics 52 49 68 10 39
1918
1898
1957
1830
1781
1968
1729
Not a pandemic
Source: Adapted from: Potter CW. J Applied Microbiol. 2001;91:

11. When will the next ‘flu pandemic occur?
Influenza pandemics occur every 10 – 68 years
Last pandemic (’68) was 37 years ago
No change in conditions (perhaps “worse”)?
Not “if” – but “when” = inevitable
When do YOU think the next pandemic will occur?
The clock is ticking

12. How many might die? (Global estimates of death)
1969 mortality
0.7 million
1968 extrapolated
2 to 7.4 million
1918 mortality
40 – 100 million
WHO range
7 to 100 million
H5N1 rate extrapolated
1 billion
Source: Davis, M. “The monster at our door.” New York, NY: New Press, Table 9.1

13. Estimated impact in U.S. of next influenza pandemic: 2 scenarios (30% AR)
Characteristic
Moderate 1958/68-like
Severe (1918-like)
Illness
90 million
Outpatient medical care
45 million
Hospitalization
865,000
9.9 million
ICU care
128,750
1.485 million
Mechanical ventilation
64,875
742,500
Deaths
209,000
1.9 million
Source: U.S. Dept Health and Human Services Pandemic Influenza Plan: Part 1. Page 18. Available at:

14. What is missing from these estimates?
Any precise explanation of how estimates were calculated
Probabilities of occurrence

15. 20th Century Influenza 1918 “Spanish Flu” 1957 “Asian Flu”
Approx. 675,000 deaths (U.S.), young adults affected
million worldwide
1957 “Asian Flu”
69,800 deaths (U.S.), mostly elderly & chronically ill
1968 “Hong Kong Flu”
33,800 deaths (U.S.), mostly elderly and chronically ill
Interpandemic Flu (U.S.)
36,000 deaths
223,000 hospitalizations

16. Source: Meltzer et al. Emerg Infect Dis, 1999, 5:659-671

17. Pandemic Planning Tools at CDC
FluAid
Estimates total deaths, hospitals and outpatients
FluSurge
Surge in demand for hospital resources duration of pandemic
FluWorkLoss
Work days lost due to worker illness or care of ill family members
Instructions to calculate 1968 and 1918 scenarios
Access:

18. FluWorkLoss: Calculate days lost

19. FluWorkLoss

20. Data Input: Work days lost caring for sick family member
Work days lost are assumptions – little or no data to support
Do numerous sensitivity analyses
Source: FluWorkloss

21. Data Input: Work days lost due to employee illness
Work days lost are assumptions – little or no data to support
Do numerous sensitivity analyses
Source: FluWorkloss

22. Data Input: employment and cohabitation rates

23. Data Input: Duration and gross clinical attack rate
Source: FluWorkloss

24. Results: 1960/70s scenario: Proportion of lost workdays:
8 week outbreak, 25% attack rate 8% 7%
Max 6%
Most likely 5%
Proportion of lost workdays 4%
Min 3% 2% 1% 1 8 15 22 29 36 43 50
Days of outbreak
Source: calculated using FluWorkLoss

25. What FluWorkLoss does not do
Measure potential impact of other factors (e.g., school closings)
Identify exactly who will get ill
Smaller the community/ firm, larger the variability
Impacts measured from “large communities”

26. Calculating 1968 and 1918-type pandemics: Instructions
Basic instructions and template of draft report
Document in Word
Use FluAid and FluSurge
Produce 1968-type and 1918-type estimates
Available at:

27. Software for estimating impact
Resource:FluAid 2.0
Software for estimating impact
(click on FluAid)
Goal: State-level estimates of impact
suitable for planning
Goal: Easy to use - interactive
Goal: Can run different scenarios

28. FluAid 2.0: Example of data entry: Can use default values or alter

29. Examples of FluAid 2.0 output

30. Illustrating surge in demand for hospital-based resources

32. Locale Y: Results: Hospitalizations by week: two scenarios: 25% AR
10,000
20,000
30,000 1 2 3 4 5 6 7 8
1,000
2,000
3,000 1 2 3 4 5 6 7 8
1918-type scenario
1960s/70s scenario
Maximum
Most
Minimum
Weeks of pandemic
Weeks of pandemic
Source: Generated using FluSurge

33. Locale Y: Results: Hospitalizations by week: 1960s/70s scenario
Pandemic Influenza Impact
Weeks 1 5 8
Hospital Capacity
# patients in hospital
566
1,873
854
% hospital capacity* 7%
24%
11%
ICU Capacity
# of patients in ICU 98
831
637
% of ICU capacity
35%
300%
230%
Ventilator Capacity
# patients ventilators 49
416
318
% ventilator use
297%
227%
* Percent of all beds: actual beds available will differ

34. Conclusions Estimates are illustrative Wide range of potential impacts
Not absolute predictions
Value: Aid in planning
Wide range of potential impacts
Plans must be flexible