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. qzm4@cdc.gov

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

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 1978-79 4,692 1984-85 40,457 B 1990-91 16,036 H3N2+ B 1994-95 24,562 H3N2 1997-98 52,148 Source: Thompson, et al. JAMA 2003; 289:179-186

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; 289:179-186

Source: Meltzer et al. Vaccine 2005;23:1004-1014 Variability: Distribution of risk of hospitalization due to ‘flu: 6-23 mths, 1974-93 (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;23:1004-1014

Hospitalizations/ 1,000 for 6–23 months: Non-high and high risk groups Source: Meltzer et al. Vaccine 2005;23:1004-1014

Influenza-related Hospitalizations per 100,000 Persons* Age Group Non-high Risk High Risk 0 - 4 100 500 5 - 14 20 200 15 - 44 20 - 30 40 - 60 45 - 64 20 - 40 80 - 400 65+ N/A 200 - >1000 *(Barker, Am J Epi, 1980; Glezen, Am Rev Resp Dis, 1987; Can J Infect Dis, 1993)

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

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

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;91:572-579

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

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, 2005. Table 9.1

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: http://www.dhhs.gov/pandemicflu/plan/pdf/part1.pdf

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

20th Century Influenza 1918 “Spanish Flu” 1957 “Asian Flu” Approx. 675,000 deaths (U.S.), young adults affected 20 - 50 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

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

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: http://www.pandemicflu.gov/plan/tools.html

FluWorkLoss: Calculate days lost

FluWorkLoss

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

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

Data Input: employment and cohabitation rates

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

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

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”

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: http://www.pandemicflu.gov/plan/tools.html

Software for estimating impact Resource:FluAid 2.0 Software for estimating impact http://www.pandemicflu.gov/plan/tools.html (click on FluAid) Goal: State-level estimates of impact suitable for planning Goal: Easy to use - interactive Goal: Can run different scenarios

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

Examples of FluAid 2.0 output

Illustrating surge in demand for hospital-based resources http://www.pandemicflu.gov/plan/tools.html

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

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

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